Email: babin_perry@yahoo.com - Repair Home Page

Introduction to Car Audio Amplifier Repair
Gulim Font Confirmation:
All modern versions of Windows are supposed to ship with the Gulim font but it seems that some computers are missing the file. The font is the best I've found for this tutorial it's clean and extremely easy on the eyes. If the text in this paragraph doesn't look like the 20px example below, I'd recommend installing Gulim. Click on the image below to go to the instructions and file link.
This is an image, not a block of text.
Background Fonts
We both know that you're not going to read this section (that has no technical information) the first time you see it but I ask you to come back and read it soon. It really is important information that will help you navigate through the thousands of files included in this tutorial.
A Working Through the Content
The Quick Links menu at the top of the directory is for use after you've become familiar with the information on the various pages. To most effectively work through the tutorial, start with the Safety page, just below the - Directory - Repair header. Work down from that point. This will make the information easier to understand than skipping around.
B Resizing Content
I don't think this is news to anyone but I'll post it anyway. For those who are unaware, you can change the size of the text and images easily by holding the ctrl key down and rolling the mouse scroll wheel (or using + or - buttons on the keyboard). The shortcut ctrl-0 resets all. Try it now if this is new to you. If you'd like, you can make the content of the left pane completely fill that pane in this way.
In some instances, you'll want to search a long page. If you go to full-screen (F11) and resize, smaller, you can scroll a lot more quickly. When you find what you're looking for, find the number it corresponds to in the list. Click one of the 'Back to the Top' links and reset the size. Then click the number in the list to go back to where you need to be.
If there are no list numbers, highlight and copy a short segment of text. Resize and then perform a ctrl-f search for that text.
The reason that the two options are needed is because the zoom can travel quite a ways from the point where you are when zoomed out.
  • Other Navigation:
    For these to work as expected, you may need to click in the frame you want them to work in (main or directory) to have them work as expected.
  • Home Key:
    The Back to the Top links are generally best, where available, but the home key will get you to the top of the page (maybe higher on the page than you wanted to go, if you're looking for the menu). The BttT links are especially helpful for those who are working away from a computer desk (i.e. on the shop workbench) and may not have a keyboard immediately available.
  • End Key:
    Same basic function as the home key but it brings you to the bottom of the page (where there is often a Back to the Top link).
  • Page Up/Page Down Key:
    These step approximately one full page height per click and will repeat if held down.
  • Insert Key:
    This one can cause confusion because there is no indication which mode it's in. Try not to click it. If you accidentally do and you try to edit text, what you type will overwrite whatever was to the right of it. To complicate matters even more, it's not recognized by all software so where it interferes with one program, it won't with others.
  • PrtScn Key:
    This one copies what's on the monitor. Alt-PrtScn captures only the active window. These copy to the Windows Clipboard. Then you paste them into something like Irfanview, edit as desired then save as the file type of your choice, in the location of your choice. Type .PNG is often best for captures with sharp text, .JPG is better for captures that are more photographic in nature.
  • Scrolling Long Pages:
    Some of the pages are long and using the scroll bar handle at the right of the frame may not work very smoothly. If you click your center/mouse wheel button, the cursor on the screen will change and moving your mouse up or down slightly will scroll smoothly. The distance you move your mouse from the point where you clicked will determine the scroll speed. After scrolling, clicking the mouse wheel again will clear this mode of scrolling.
Background Color and Font Options:
For those who are really interested in this type of work, you will spend significant time with the tutorial. To help make it better for you (visually), there are now options for font and background colors.
Previously versions of the tutorial had strict font control but in recent re-writes, the control over the fonts was largely left to your discretion and will be whatever you choose. Arial or Verdana are web-standard fonts. Those two are OK for short periods but not for extended reading. If you have it, Gulim is a very fine/thin font that sometimes works better than the two previous suggestions. The likely default is 'Times' which is hard for me to read for long periods. Depending on the monitor, fonts from 14 to 24 pixels may be options for various readers. My preference is Gulim at 20px and that's what's set in the .css file (it can be changed). If you find yourself using the zoom feature (ctrl-mouse scroll wheel) often, you can change the default font in your browser. THIS page (more important than you might think) has several examples if you're not familiar with fonts.
If you're using one of the browsers (other than the recommended Safari or Chromium portable) that doesn't allow you to set a suitable font or adjust the font size (Maxthon browsers or the older Opera 12.14), you can set the font face and size in the .css file. Email me at the following address if you need help doing this.
babin_perry@yahoo.com
New options for the background have also been added. These options are not quite as simple as clicking a button but they only require that you:
1. Open a .css file in Windows Notepad (nothing else). 2. Copy and paste a number or name into a specified location (simple). 3. Save the .css file and reload the tutorial page to see the results. Change until you find what you like the best.
Remember that links for both the background and font instruction pages are at the top of this yellow table and that this page is the second one down from the top, in the directory.
C Flash Content in this Tutorial
This should have been resolved before you purchased the tutorial but if it wasn't...
This tutorial uses Flash graphics extensively. If you're using a mobile device like the iPhone or iPad, it's likely that you won't be able to view most of the interactive content because many of those devices can't display Flash graphics.
Using the right hardware and software:
To get the most from this tutorial, use it with a standard desktop or laptop computer with a full-sized monitor and a mouse/trackball. Use a Flash-capable browser. If you contacted me before purchasing the tutorial, it's likely that we've already confirmed that you have a suitable browser. If you want to find a different Flash-capable browser, go to THIS page or email me at:
babin_perry@yahoo.com
There may be instances (in some browsers) where you may not be able to enter values into the Flash graphic text fields if you try to enter them where the graphic resides on the page. If that happens, click the link below the graphic to open it in its own tab. This should resolve the problem. If not, email me.
Possible Monitor Options:
Today's monitors are typically in a wide-screen format and generally best suited for watching movies. They are not really formatted for viewing long pages. To see more, at one time on your monitor, you can go to full-screen mode. To toggle full-screen mode, use the F11 button/key. This will increase the effective height of your monitor.
If you're familiar with the operation of computers and hardware and are using the tutorial on a high-resolution, wide-screen monitor (which the tutorial doesn't need), you may want to rotate the monitor 90° and use the monitor in portrait mode. This is done by some who code or produce large vertical text documents. Do this only if the computer is exclusively used for the tutorial. It may not be suitable for daily use for other content.
I finally got around to doing THIS after repairing a monitor that needed capacitors (huge surprise :). It works well but takes a bit of getting used to.
If the monitor in portrait mode isn't quite wide enough to fit the two frames, there are a couple of simple options. One is to grab the frame between the main and directory and drag it over toward the directory. The other option is to right-click the link in the directory that you want to open and select open link in new tab. There is an Easter egg in the directory cells. If you click the upper corner of the cell, that will open that cell's link in a new tab.
Above, it was stated that you don't need a wide-screen monitor for the tutorial. An older 19" 4:3 monitor with a 1280 x 1024 resolution will work well (for normal mode, not portrait). Larger than 19" is a bit better but not necessary. I used an old Dell computer with a monitor on an articulated wall mount. The keyboard and mouse were wireless but I so rarely used the keyboard, it was only important that the mouse be wireless. If you have a neat workbench, neither needs to be wireless. What made it work so well was the articulated wall mount for the monitor (monitor had a VESA mount). Many people use laptop computers but with that, you lose all of the bench-space taken up by the keyboard of the laptop. With the wall mounted monitor, you lose absolutely no bench area and the monitor can be pulled in close when you need to see fine details on a diagram or datasheet. The vertical display may not be everyone's choice but the rest of the suggestions work well.
Side note... If the only option is a laptop computer, you can do this with an external monitor plugged into the laptop.
One last note... The most basic, 10 year old Dell or HP computer running Win7 will do all you need, to use the tutorial. Ask around and you'll likely find people willing to give you computers that are just taking up space.
Pre-Loading:
This pre-loading will work anywhere in the tutorial (except the Quick Links) and will prevent waiting for pages to load. If you want to open any/all of the tutorial links in background tabs so they will load and be ready when you switch to them, right-click >> open link in new tab.
Flash:
The embedded Flash files have advantages that make them useful. The vector aspect of the graphics means that they are essentially infinitely scalable. They will remain sharp, regardless of the magnification. They will, in some cases, contain large raster (photo) files. These take significant resources when used at high resolution. Many of the pages with these large files will cause slower computers to hesitate when you scroll over the large files. If this becomes a problem, grab the scroll handle and scroll the full length of the page several times quickly, the browser will store the files in RAM and from then on (until you leave the page), the page should scroll smoothly.
For all Flash files, you can zoom in (right-click and select from menu). To navigate when zoomed in, use the left mouse button (click, hold and drag). When opening a Flash file in a new tab, go to full-screen mode (F11) or at least maximize the window.
The various Flash diagrams can be printed at high quality if you open them in the stand-alone Flash player (if you installed all four Flash Player files). For many Flash diagrams, there is a link to open them in the new tab. If you copy the file name from the address field, find it in the tutorial files, in the Windows file manager and open it by double-clicking it there, it should open in the stand-alone Flash Player. From there, you can print it.
Remember that you're not limited to printing to paper. You can print to PDF and other formats. The options are likely in the printer options dialog box.
When you open a Flash file (extension .swf) in the stand-alone Flash player, it allows printing but there is another option for a small number of .swf files. There will be a .exe file with the same base file name as the .swf file. Many people will panic (for good reason) when they see a Flash-related .exe file. These files are harmless. They allow printing if you don't have the stand-alone flash player installed. Your anti-virus will likely warn you and scan it when you click on one but all will come back clean.
D Mains Voltage and Damage to the Scope Ground
The Term 'MAINS':
You will see the term 'mains' in the body of this tutorial. The term refers to the AC voltage supplied by the electric utility company. In the US, it's 120v, 60Hz at common wall outlets. Another common mains voltage is 230v, 50Hz. There are many others.
Connecting a mains-powered scope's chassis ground clip (generally connected via a banana connector on the front panel of the scope) or scope probe's ground clip to anything other than a 0v ground can damage the scope because the scope's chassis ground is typically connected directly to the mains ground. The GND on the scope in THIS image is obvious, as is the probe's ground clip lead.
For many 12v power supplies with 3-prong power plugs, the front panel output 'ground' terminal is also connected to that mains ground.
If you connect either of those scope grounds to power source (±voltage) inside an amplifier, the scope and/or the amplifier could be badly damaged because that voltage will try to pass through to the mains ground via the 3-prong mains power plugs. You'll essentially be shorting that supply voltage to ground. This can lead to excessive/damaging current passing through the scope's ground circuit because the large bank of capacitors, charged to high voltage stores considerable energy and that energy will be discharged into your scope.
THIS page has information that will help prevent you from using a damaging ground point for your scope.
E My Shorthand
:
You will find an unending number of dagger (AKA obelisk, or obelus) symbols of various colors. These allow explanations of various pieces of information without having a comma-enclosed comment several sentences long inside a paragraph.
There may be 10 yellow daggers per page but the small dagger (with paragraph text) and large dagger (below, on its own) open/close that colored pair. If you see another small dagger of the same color later on the same page, look for it's larger mate shortly below it (could be several paragraphs or images below).
~:
If you see the character '~', it means approximately. For example, ~15v means approximately 15v.
±:
If you see the character '±', it means positive and negative. For example, ±15v means positive AND negative 15v. This is commonly used when stating the output voltage of the various power supply circuits (±15v, ±rail voltage, etc.).
B+:
B+ is the positive battery terminal connection on the amp or the positive 12v source (depending on the context).
TNFG:
TNFG means Take Nothing For Granted. Confirm everything that could make a difference for the circuit you're troubleshooting. Make no assumptions.
xxx:
If you see a part number that has a lower case 'x' as part of the part number but the other letters of the part number are upper case, it means that there are several versions of the same basic part. For example the TLx94 could be a TL494 or a TL594 but, for the context, they are similar enough so that the TLx94 would cover both parts. The same goes for the L7815, L7805, L7809.... If the context was for the L78.. regulators in general, they would be referred to as the L78xx regulators.
Weeds:
You'll see 'a trip into the weeds' (or something similar) throughout the tutorial. These are (generally) short tangents with something that may be of interest. It's not generally completely useless information but may not be perfectly in line with the more relevant content on the page. For long paths through weedy areas, you'll generally have an option to skip over it.
Part Number Clarification:
If you see a lower case 's' at the end of a part number (particularly one that has other letters in upper case), that's the pluralization of the part number and is not part of the part number. For example, If you're instructed to replace the 'IRF3205s' in the circuit, the part number is IRF3205, not IRF3205S. There may be instances where you will see something like IRS21844S. The capitalized S suffix is part of the part number. IRS21844Ss would be plural.
There will be instances where multiple pins of an IC will be referenced. Let's say it's a TL494. If the pin referenced is pin 14 (which is the 5v regulator output pin, by the way), it may be referred to as 494-14. If there are multiple TL494s and they are designated as IC601 and IC602, that same pin of IC602 may be referenced as IC602-14.
PDF Page Number:
You will have to use PDF files with the tutorial. If you see it written that you need to go to 'PDF' page xyz, that means the number in the page indicator on the toolbar of the PDF reader. There are instances where the numbers on the original printed document don't match those of the PDF file. This should make it clear on what point of the document you should be looking, for the information.
Map Reference (MR):
In some documents like PDF diagrams (and maps), there are numbers across the top/bottom of the page and letters down both sides of the page. These are used to give a reference location on the page. This helps you to give the location of a part that may be difficult to find. For THIS diagram, if you were told to check Q126, you may be able to find it quickly (maybe) but if you were given the page number and the location/reference of page 1, F6, you could go directly to it. If you're using PDF Xchange Viewer, zoom out, align the horizontal and vertical markers (they show mouse x-y positions) to F and 6, then use ctrl-roll mouse scroll wheel to zoom in on that point.
PDF File Links:
There will be instances where you will click a PDF file link and it will open in a browser window. The application used by that browser may not be ideal. The file location will be shown in the browser's address field at the top of the browser window. You can:
  • Navigate to that folder and double-click the file to open it in the default PDF viewer
  • Or, copy the entire address, open your PDF viewer, choose the 'open file' option and paste the entire address into the file field at the bottom of the window.
  • Or, copy the entire address, open the Windows file manager (Windows Explorer, File Explorer) and paste the entire address into the address field at the top of the window and click enter. This will work for any files that have a default application associated with the file type.
  • Recommendation: PDF Xchange Viewer. It's fast, free and works very well.
  • You should have installed Safari for times like this. Safari is FAR superior to other browsers when you will encounter files/folders and PDF files. Other browsers open the PDF files in a generic PDF browser. Safari opens it in a Safari window but it opens it in your default PDF application. This retains all of the features you expect (including being to navigate with the hand tool). Safari !! If you see a horizontal rule at the top of a page that is colored like the one below, instead of the normal gray, the page will be nearly impossible to use, as intended, with anything other than Safari.
[ ]
PDF Viewer Access:
If you want a quicker way to access your PDF viewer, there are several options. The easiest is to pin it to either the Windows Start Menu or the Windows Taskbar. In Win7, all you have to do is right-click on the PDF viewer in the list of software/applications (instead of left-clicking, to open it) and select pin to either the Taskbar or the Start Menu. You can also send a shortcut to the desktop. Same process as before but you select Send To >> Desktop (Create Shortcut).
F Use the Suggestions as Starting Points
There are many tips in the tutorial. Most work well for me and probably will for most people. Use them as a starting point. You may (will) find a way to perform some tasks in a way that will work better for you... but, when first getting started, don't spend time TRYing to reinvent the wheel. Instead, spend time learning the material.
Although many tips will be in sections for a specific type of amplifier, don't let that give you tunnel-vision. Many of the tips can work for other amps, as well.
G Markers
For sections that contain checklists, important information or graphics, I've added markers. For text... copy the text between the markers and paste it into a text editor (Word, Notepad, Wordpad...). For items that cannot be copied and pasted, there will be specific instructions. Print the items and keep them handy for the first few repairs. If you see a '' next to a link in the index of a page, that indicates it's a section where you'll find the markers.
H What You Need to Know About the Links
There are many links to other pages. Many times, the link is to a point in the middle of another page. If your computer's hard drive isn't fast enough, the place where you land may not be precisely where you want to be. This means that you won't see the information that you're expecting to see. If the page loads in the same pane of the browser (to the left of the directory), let the page load completely (will take 3-4 seconds) then go BACK and click the link again. Generally, the second time you go to the page, you'll land in the correct location. For pages that open in a new tab, let the page load, close the page then click the link again.
For those who cannot get the page to load properly, I generally have the name of the page and the item number on the page. It will look something like this:
flameproof and fusible resistors (Resistors and Capacitors page, Item #6)
For links (both images and entire pages) that pop-up new tabs, close the new tab (ctrl-w is often quicker/easier than using the mouse to click the x) after your done with it. If you click another link and the pop-up window is in the background, the linked page will open in the background window and you may not realize it (leading you to think it's a dead link).
'Ghosted' Text:
There will be some text that will be barely visible (like the 'Back to the Top' buttons/links that you'll find on many pages). The text is generally non-critical and could be insignificant comments, options/links... If you left-click and drag to highlight the text, it will become clearly visible.
'Ghosted' <I:
If you see <I where you would expect to see a blank space, it's a snippet of information that will show up in a balloon if you place your mouse cursor over it.
Highlighted Links in the Directory:
There are some links in the directory that have a rectangle around them. These links are for pages with a heavy load (multiple Flash files and/or a large amount of content). These will take longer to load in Safari. The left-hand pane may turn white or seem to freeze until the page loads. For Safari, the wait can be up to 10 seconds for loading (but will depend on your computer), the first time you visit the page. After that, Safari should cache the page so subsequent visits will load more quickly.
Types of Links:
The following applies to the pages where all links are color-coded. There will be some links that open in new tabs. You can close the new tab after reading the pertinent information. There will be no 'back' option on these tabs/pages. When you click a link that doesn't open a new tab, it's likely that you're being redirected to a point on the same page that you are on. In those instances, selecting the 'back' option will get you to where you previously were.
  • A link with this color underline is an external link and best used with Chromium portable. Expect Safari to fail for any external (pink) links. These are typically the only links outside the tutorial files.
  • A link with this color underline is a link to a pop-up image. In Safari, it will open a new tab. To clear it, close the tab. In Chromium, it will open a pop-up window which needs to be closed.
  • A link with this color underline is an internal link. It will open a new tab. To clear it, close the tab.
  • A link with this style (gray) underline is an internal link but the content is on the same page that you're currently viewing. Clicking that link will bring you to the relevant point on your page. This is the only type of link, for most of the pages of the tutorial, where the 'back' button will be used to bring you back to the previous point you were viewing.
External Links:
The two most common browsers for the tutorial are Safari 5.1.7 and the portable version of Chromium. I like Safari but some of the external links won't work with it. Using Chromium portable may eliminate the external link problem and still give you the ability to view all of the Flash graphics.
With the ever-changing internet, some links will go dead. If a link no longer works, you can generally use a search engine to find the information you need.
Internal File Manager Links:
One advantage of Safari is that, when you click on a link to a Windows folder/directory, it opens the Windows file manager. This means, if you have an image viewer that allows you to scroll through images with a click or roll of the mouse scroll wheel, you can do so (IrfanView, highly recommended). Safari will also generally open files in their native/default application (important for .PDF files), instead of opening them in the browser's internal PDF reader, as Chromium portable does.
As far as I can tell, no version of Chrome will use the native applications. For graphics, every image is a separate link that you have to click. If you open the Windows file manager (Windows Explorer, File Explorer) directly and copy/paste the link into the address field at the top of the file manager and hit return/enter. This will bring up the folder and allow normal file interactions. More on this, below.
Navigating directly to file locations is much quicker if you have the Everything Search Engine installed. Drop a folder or file name (not the complete file link) into its address field and it immediately comes up. It works especially well if you can only remember part of the file name. Start typing and the possible file names start to come up. The more you type, the shorter the list becomes. When you see the file that you want, you have a couple of options. Either double-click to open the file or right-click it and select 'open path' to open the folder with the file you searched for. To test this, open Everything and start typing *500a2* or *200ix* in the Everything address field. The most efficient way to search is to type two asterisks and then start typing between them. You will see that it makes it very easy to find files, by name. Bear in mind that it doesn't search contents of files which will generally make it much quicker than the native Windows search.
The Windows Key:
By using the 'Windows' key + e, you will be able to open the file manager, directly.
You will see the following block of instructions (or a 'navigate' link back to here) in various parts of the tutorial. This helps you navigate much more efficiently.
Click the link above if you're using Safari (preferred browser for opening files and folders).
If you're using Chromium Portable, copy the link address (right-click link and select copy link address) and drop into the address field of Windows Explorer. Using the Windows key + E will open the Windows Explorer file manager.
^^^ Try this now ^^^
with both the Safari AND Chromium Portable browsers
  • Notes/Review:
  • There may be instances (in some browsers) where you may not be able to enter values into the Flash graphic text fields if you try to enter them where the graphic resides on the page. If that happens, click the link below the graphic to open it in its own tab. This should resolve the problem. If not, email me.
  • THIS is what you will see if browsing files/folders with Chromium. THIS is what you'll get when browsing the same files/folders with Safari.
  • Safari won't work for most external links. Use Chromium or, when Chromium portable won't work with the external links, copy and paste the link into your preferred online browser. You won't miss much, externally. Most are links to McMaster. For most links in the tutorial, Safari is far better than anything else.
  • When you go to paste the copied address into the address field of Windows Explorer, the word 'computer' will be there. Click on a vacant part of the address field and the background for 'computer' will switch from white to the default system color (generally blue). At that point, you can right-click in that field and paste the address. Then hit the 'enter' key to go to the folder with the files for that link.
    ^^ Will work for copied/pasted addresses that have the full file link (like the one below, small text so it would fit on one line) and will open folders in Windows Explorer. It will generally open files in their native viewers (good for PDF files). You can copy the text below and try it in Windows Explorer. Use the Windows key + E to open it as suggested above.
    file:///C:/power%20supply%20tutorial/power%20supply%20tutorial/repair_tutorial/miscellaneousstuff/jbl/bp1200p1_sm.pdf
    For partial names, use the Everything search engine (if you have it installed) and the asterisks (for more thorough searching) from inside the repair tutorial folder. When you right-click, THIS is what you'll see. Choose the Search Everything option and search as suggested.
  • The various links in the tutorial are generally set up to open in a new tab. If you click the links (as you should), you can have too many open tabs if you don't immediately close them. If you find one that you want to keep open but want to close the rest, right-click that tab and select 'close other tabs'. That will leave you with only the selected tab open.
    To keep more than one open, slide all the tabs you want to keep open to the left. Then use the option to 'close tabs to the right' (not an option in Safari).
CTRL-F:
Many keyboard shortcuts perform the tasks immediately but some like control-f require input. Control-f is 'find'. It brings up a dialog box or text input field and allows you to enter a word or string of text when you hold down the control key and while it's down, you press the F key. This works universally on virtually every Windows application. The Windows 'find' function is very thorough and therefore can take a relatively long time to complete a search. The wider the search field (the entire computer), the longer the search time. Searches of relatively small volumes, like the tutorial, don't take long... AFTER Windows has indexed the files. It does this, generally, when your computer is otherwise inactive.
The 'Everything' search engine recommended on the TT10 page (and above - it's wonderful software), item #22. The Everything search engine only searches file names but if you know the file name or any part of it, the returned file list is almost instantaneous.
As an example, I searched the tutorial for 500m (an amp model) with both the Windows SE and the Everything SE. Windows returned 85 items. Everything, only one (which happened to be the one I needed). Try it for yourself if you installed Everything.
I Component Part Numbers
Throughout the tutorial, you will see various part numbers for various components. The semiconductors that are available from the various manufacturers are not available forever. Some are available for only about a year. Some for 20 years or more. There is no way to avoid using part numbers and there is no way to suggest replacements that will be available forever. Although the semiconductors are the biggest problem, this applies to various other components as well. Keep this in mind when you come across obsolete part numbers. The part numbers used as examples were the ones available at the time that that part of the tutorial was written.
In some instances (the output transistors in class D amplifiers, especially) replacement semiconductors that are compatible with the circuit may be difficult to find. To find working/suitable replacements, it may take a bit of comparison of specifications and then extensive testing, trial and error. Some class D circuits may require a bit of re-design to get them reliably repaired. Keep this in mind when you find that an amp uses obsolete transistors when you give a quote to repair the amp.
J Radio Shack References
There are quite a few references to Radio Shack items. At this time, RS is still in business and still has some stores open. Even if Radio Shack disappears, some of the items mentioned in this tutorial will be available on eBay. As a side note (and possibly only of interest to those who grew up with Radio Shack catalogs) there is a great site that has old Radio Shack catalogs that you can browse. When you need a break from the tutorial, visit the SITE. if you're using a browser that won't work with the link:
http://www.radioshackcatalogs.com/catalog_directory.html
K Another of the Easter Eggs
For those who read the information in the yellow table above (again, that information is VERY important)... If/when you visit this page again, you can skip the content in the yellow table by clicking the 'Introduction to Car Audio Amplifier Repair' line of text above the yellow table.
If you used ctrl-mouse scroll wheel to resize this page, remember that you reset the zoom with ctrl-0.
Now onto Amplifier-Related Content
This can Make Repairing Car Amplifiers Relatively Difficult:
Getting the bad news out of the way, first... One aspect that makes doing this work more difficult is a lack of technical documents (service manuals, schematic diagrams, revisions, test procedures...). Do not expect any support from the manufacturer. It's rare. Some go as far as to deface parts to make it more difficult to repair the amp. This is especially true for the Brazilian types of amps (some are from Brazilian manufacturers and some are Chinese knock-offs).
If you're in this for profit (<< not a dirty word) and won't see many of the amps for which you have no support from the manufacturer and that have defaced components (especially the output transistors), PUNT. Let the owner send it to the manufacturer for repair. Don't let them make their problem your problem.
If you want to experiment with repairing an amp using parts that you believe will be reliable replacements, only risk this if you know the owner VERY well. Experimentation is a much better choice if you're working on amplifiers that you purchased to 'practice' on. Be aware that, just because the amp works for a short while in your shop, that doesn't mean it will be reliable long term. If it fails, prepare to be married to it.
If you're struggling to survive and you have the chance to repair a problem amp like this, don't. It could get costly (both time and money) and you don't need that if circumstances are already difficult.
Executive decisions like the one above will come up repeatedly. Make the ones that are best for you. There's nothing that says you have to repair EVERYthing that comes into your shop. I did this when I was first starting out... don't.
Properly repairing some amplifiers can be time consuming and to properly repair an amplifier means that all aspects of the repair are addressed. This includes properly adjusting the protection circuit components for some amplifiers (many of the Brazilian and Chinese amplifiers that have defaced parts). To get an idea of what's involved with a proper repair on those amplifiers read THIS page. The process is not trivial.
Repair Related Conversations:
For most all conversations related to the repair of the amplifier, it's best to have documentation. This is generally best done via text/email (email preferred) so that there is a clear record of the discussion and agreements as to the work expected, prices, warranty... This protects both you and the customer.
When contacting the customer, it's important to have one long email thread. This will make it less likely that fragmented messages will get lost. In all replies, let the previous email remain inline. This makes multiple copies of all messages in both the incoming and outgoing emails.
You may think that you missed nothing when you did the initial troubleshooting but initial troubleshooting can't generally find all faults and most definitely can't locate parts that are weak (fail unexpectedly during testing). Any time that you encounter a problem that could lead to a dispute, clear it up with the owner before you do anything more. It takes just a few minutes to send an email and costs nothing. After you get more experienced, you can adjust the policies regarding this to best suit your needs.
This will be mentioned again but you need to be aware that some customers will not pay for an amp that's not repaired up to their expectations. Some will expect a 20 year old amp to be 100% as when new (mechanically, as well as electronically). Through conversations, you can help determine what they expect. If the owner seems dodgy, punt! Just tell them you can't repair it. Do NOT tell them that you can't get the parts because some will want the part numbers and will try to get the parts themselves.
People can be Vicious:
Bear in mind that misunderstandings can wreck business relations and ruin your reputation if the owner of the amp feels he has reason to slander your good name... And many people become vicious if they feel like they're a victim (justified or not). Remember that, nowadays, the goal of too many people is reaching the status of victim. Victimhood gives them a way to get sympathy and being on the receiving end of sympathy floods their brain with feel-good chemicals (dopamine?) which gives them (as an addict to those chemicals) reason to carry out a vendetta against you.
And while in the neighborhood of dissatisfied customers... If you repair an amplifier and someone refuses to pay you because there is some sort of conflict on the final repair, do NOT pull parts and send it back with missing components if it was complete when you received it. This will give the owner a reason to ruin your reputation on social media or possibly through the BBB. Bagging and retaining all FETs until the repair is complete (repair paid, amp installed and working) is a good practice.
One of the problems with repairing amplifiers is that some parts are no longer available. This is especially true for custom manufactured components (potentiometers [there are so many variables], terminal blocks...). There will be times when the amp has to be made functional but it may not look OEM. This is a problem for some customers.
Price Quotes:
The right price for services sometimes comes up and there is no universally correct number. Factors such as overhead, the amount of work available and the market you're in will all make a big difference. Quotes and initial troubleshooting are covered, in more detail later on this page. On the TT2 page, item #13 has more information on giving quotes.
Questions about Brazilian Type Amplifiers:
This tutorial is intended to give you an expansive knowledge base for most all types of amplifiers, not only one type of amplifier. Brazilian amplifiers and their Chinese knockoffs are popular (mainly because they're cheap) and you may be looking for information on the specific Brazilian amp you have. There are just a few specific Brazilian amplifiers here but they really aren't that special. Except for their microcontrollers, they use off_the_shelf semiconductors. In that respect, they're like most other manufacturers. They sometimes design their circuits a bit differently but, if you put forth the required effort to understand the components covered in this tutorial, you will rarely have trouble repairing one... with the exception of finding the part numbers of defaced parts.
It's bit early to go into details but the term microcontroller (AKA MCU, µ-com or microprocessor) refers to an IC that can be anything, with reference to control circuits. The pins on it can act as inputs or outputs and the ICs have to be sourced from the manufacturer or one of their distributors. They cannot be purchased from normal electronics parts distributors. Think of them this way... They are essentially the same as a big pile of lumber and building supplies. What are they going to be? They could be virtually anything. Without documentation from the manufacturer, you don't have a clue what the various pins are, except for the power supply pins. When you get a Brazilian type amplifier in for repair and the amp doesn't function normally, there isn't much you can do if the MCU is the problem. Add to that, if you damage the MCU accidentally and cannot get a replacement, you just turned the amp into a paperweight.
Initially, avoid any of the Brazilian amps with defaced parts. Only about half of the Brazilian type amps have defaced components. When defaced, the original markings will be sanded/ground off and (generally) a single alpha-numeric mark will be stamped into the face of the component. For amplifiers with re-marked components, tell the owner what the manufacturer did to the parts and that he will have to return it to them for repair. This is not a reflection on your ability to do the work.
Initially, avoid any of the Brazilian amps with defaced parts. << Repeated intentionally.
THIS link is a meeting place for most all of the Brazilian-specific amp information. Read that entire page (not just from that link's landing point). Follow the links on that page and perform the searches as suggested and you will find quite a bit of relevant information for Brazilian type amplifiers.
The IRS2092, IRS2093 and IRS20957 Driver ICs:
These two ICs, when the output transistors are defaced, are some of the most problematic because if you can't determine what the original transistors were. This is because you will have to re-calculate the protection circuit components and/or perform extensive testing (possibly destroying various components) to ensure that you have properly repaired the amplifier. Virtually no one will do this as they should and why I recommend that you avoid any amplifier with defaced transistors, especially if the driver ICs use the on-board over-current protection.
When I asked why different techs weren't doing this, I received responses, some of which bordered on being abusive. Some people become irrationally defensive when you question their competence.
On-Board Over-Current Protection:
Most amplifiers use current shunt resistors and an external comparator (all to be covered in detail as you work through the tutorial) to detect over-current. This allows the use of virtually any replacement FETs of sufficient voltage rating... at least for initial testing.
Most of the amplifiers that use the 2092/20957 ICs utilize the internal/on-board over-current protection. If you have a bank of output transistors that has no FETs in it, the amp is likely to go directly into protect mode. This prevents you from checking drive signals, as you could with other types of class D amplifiers. If you try to use replacement FETs that are not identical to the original FETs, the amp could misbehave in a couple of different ways. It may go into protect prematurely (possibly even on startup) or it could fail to go into protect when it should (shorted speaker or wiring...). Ways to make these ICs behave well enough to allow proper testing will be covered in detail, later in the tutorial.
Redundant and needs to be...:
If you're working with an amp with defaced FETs and cannot get definitive answers on their part numbers, THIS page give some options. If this amp is likely a one-off repair and you're unlikely to see any more like it, it's not likely to be worth the time/effort to repair it properly. Let the owner send it back to the manufacturer or their authorized repair center.
To cater to those interested only in Brazilian amplifiers, I've tried to include the word Brazil in the text related to components and circuits commonly used in Brazilian amplifiers. Perform a ctrl-f search for Brazil on each page of the tutorial to see what relevant information there is for those amps on that page. This isn't the right way to learn to repair amplifiers but the request is so common that I've given up fighting it.
A 'Short':
The term 'short' or 'short-circuit' is going to repeatedly be used so we need to define it. Terms/components in the following graphic may not be familiar but what's important are the general concepts. The term 'short-circuit' (often reduced to 'short') simply means that, in some electrical circuit, the current is flowing through a shortened path (not flowing through the entire circuit that it's intended to be flowing through). When this happens, the most common effect is excessive current flow which often overloads components and causes various failures.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
A short can be due to a component failing (like those represented above) or by something bridging circuit points. One example of this could be the primary windings of a transformer shorting to the secondary windings of the transformer when they should be isolated from each other.
There have been many times where wire strands (from people stripping wire near the amp) have shorted components in an amplifier. Other times the short can be from a technician allowing their meter or scope probe to slip and bridge adjacent component terminals. Many of the ICs operating at relatively high voltages, like the audio driver ICs in class D amplifiers, have virtually no chance of surviving an accidental short between terminals. This why it's important to keep your meter probes sharp.
This is a significant problem where finely stranded wire is used. It's nearly impossible to strip it without losing a few strands. Too many people strip wires directly over the amplifiers. Even if it's stripped near the amplifier, strands can get into the carpet and work their way into the amplifier. If you see strands of wire in an amplifier, explain what has happened, what to avoid doing in the future... and tell them to carefully vacuum the carpet in the vehicle to remove all stray strands of wire.
Errors in Service Literature:
When you find an OEM service manual or schematic diagram that exactly matches the make/model of the amplifier you're servicing, don't assume that it will be 100% accurate. There are mistakes, revision changes, engineering drawings that were never supposed to be released, part obsolescence... You will rarely find a 100% perfect match for the amp you have. Use common sense, look at the circuit design and try to determine why there is a difference. If the part looks original (section on that upcoming), leave it as-is unless you have a very good reason to change/replace it.
Help me to Better Help You:
There is a good chance that you will ask me to help you with repairs. This is expected. One problem that needs to be avoided is sending me poor/erroneous/incomplete information. One of the worst is when I ask for voltages and people are too lazy to give exact meter reading. Now, I don't want the exact meter reading if you're using a Keithley 2002 meter<Iwith 8 digits to the right of the decimal (2v range) but I do want/need the 3 digits to the right of the decimal when asking for meter readings... even if they are zeros If you're using a standard multimeter, give me precisely what's on the display for whatever reading I'm asking for (voltage, resistance, diode-check readings on components...).
Think Logically:
I know it's generally an ancient concept but common sense is important. Use what you have and develop that ability. Think logically. On far too many forums, I've seen people throw out suggestions that made very little sense and were only very rarely useful (and even then, only by luck). When you start to make a change, of any type, carefully think about what you're trying to achieve and whether the proposed change will do what you want.
Common Sense Defined:
Ordinary sensible understanding; one's basic intelligence which allows for plain understanding and without which good decisions or judgments cannot be made.
The American Heritage® Dictionary of the English Language, 5th Edition
Don't do anything blindly. If that's how you're going to try to do this work, you have very little chance of ever being a competent technician. If you don't perform tasks/troubleshooting in a logical manner and ever encounter a real tech, you'll be considered to be a hack, or worse.
Initially, you will use what you know to think through various problems, replacing only those parts that need to be replaced. Occaisionally you may encounter problems that could use a bit of guesswork but those are rare. If you are struggling with troubleshooting a problem, email me and I'll try to help. Troubleshooting via email isn't perfect but it's generally successful.
babin_perry@yahoo.com
You'll see the word 'competent' used repeatedly. There are people who can get an amp back to functioning but far fewer who completely understand the circuits and strive to deliver an amplifier that's at least as good as it was originally. Slight improvements can often be made in the protection circuits to make the amp more reliable. The information provided in the tutorial is what the average working technician would know after several years in the business. The knowledge would likely cover different amplifiers but the level of knowledge would be equal.
Powering an Amplifier During Testing:
If you're asked to provide the voltage on various points in a circuit, unless otherwise directed, you must have a 12 volt supply voltage applied to the B+ and remote terminals of the amp and the amp ground connected to the ground terminal of the 12v power supply. Rarely, you may be asked to leave the remote terminal with no voltage applied (so the amp wouldn't power up normally) but, again, that would be rare. Powering only remote (no 12v supply voltage connected to the B+ terminal of the amplifier) is common when checking power supply drive signals in older Rockford amplifiers. << Ground isn't mentioned but you will never likely be asked to power up (in any way, for any reason) without ground connected. There is an advanced form of troubleshooting that will require not having the amp grounded but that is not performing any test on the amplifier, as an amplifier. It's used to find defective components.
'12 volts' (12v, B+, anything similar) is going to be a generic term used for the power supply for amplifiers throughout the tutorial. This is adopted from the 12v automotive charging system which isn't exactly 12v but that's an easy way to refer to it. Car amplifiers are typically designed to operate from about 10.5 volts DC to about 16 volts DC because the actual charging system voltage in a vehicle can vary quite a bit. Anyway... 12v in this context means a DC power source that is of suitable voltage (12v-13.5v, is optimal) and current capacity (will vary greatly depending on the task at hand) to power-up a car amplifier.
This is for amplifiers that have only the remote turn-on input to control the amplifier being on/off and without that remote voltage, the amplifier's power supply (and therefore the amplifier) would be shut down. There may be amplifiers that use signal-sensing on the RCA inputs (may be used if you're using a cell-phone for the signal source, which has no remote turn-on voltage to send to an amplifier) or DC detection (often used to sense when an OEM head unit with a bridged internal amplifier is being used as the signal source). The second two examples are a different can or worms, so to speak
Colored Text Corresponds to Circuit Points in the Graphic Below:
Above, 'B+' was noted as a possible 12 volt designation (as B+ and ground). When you see B+, look at the context. For the input to an amplifier, it's 12 volts. If you see it as the designation for the positive supply terminal of a 'chip' (Integrated Circuit, IC...), it could have a different meaning. For example, you will see circuits with positive and negative supply voltages of B+ and B-. In that context, the B+ would be a +15v supply and the B- would be -15v and having a negative component, you would know that it comes from the output of the amplifier's switching power supply. I know that much of this language is foreign to those new to amplifier repair work but just read along and all will become clear.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
The terms/abbreviations chip, IC, I.C., Integrated Circuit may be used interchangeably through the tutorial. The term 'chip' is not really acceptable when referring to ICs so I'm trying to replace it where appropriate. Where it is more acceptable is when referring to small SMD (Surface Mount Devices) i.e. chip capacitor, chip resistor...
±15v:
Sorry for all of the clarifications but some people are very new to electronics and this needs to be done. The ±15v specified in the previous text is another generic value. This is intended to be the supply voltage for the various preamp ICs like op-amps. The actual voltage can vary. Rockford uses supplies as low as ±9v (specified as ±9 but actually a bit higher). MTX commonly uses ±18v. ±15v is nothing more than another generic value like 12v was used, above.
Negative Voltage:
When I was just starting out, the concept of negative voltage was very confusing. It shouldn't have been. It's all about a reference point. If you're in a 3-story building and on the second floor, you can easily understand that you have one floor above and one floor below. Voltage is all about reference points and for a multimeter, the point where the black probe is placed is the reference.
If you have two D-cell batteries in a flashlight, stacked end to end (connected in series), the flashlight will operate off of 3v (each battery is 1.5v). If you place the black probe on the negative of the 'bottom' battery and touch the top terminal of the top battery with the red probe, you will read 3v. If you touch the black probe to the center of the two batteries and the red to the negative terminal of the bottom battery, the meter will read negative 1.5v...
Enough Blah, blah, blah...
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
Fuses:
If the amp has on-board fuses, all fuse holders should be filled with the correct fuses (as designated by the manufacturer). All fuses should require a bit of force to insert and remove them. A loose holder could cause an intermittent connection or could cause the holder to overheat and melt, making it unusable. This can present a problem for you if you repair the amplifier only to find out that the holder is defective and not available as a replacement part. This may mean that you won't get paid for the repair if the owner wants the amp back to original condition.
You should read 0 ohms (or whatever your meter reads when it's set to ohms and the multimeter probe tips are held tightly together) across each fuse when they are out of the amp. There are many amplifiers that have multiple fuses in parallel. For those, having a single good fuse when all others are blown would make all look good (read 0 ohms). If any fuses (out of the amp) read as open (no change in the meter display when the probes are touched across the fuse terminals), they need to be replaced. More on fuses can be found HERE. Read down, at least, to 'Fuse Taps:'.
Checking the Meter and its Leads:
Each time you use your multimeter (to check anything, for voltage, this is even more important), you should set the meter to ohms and hold the metallic probe tips tightly together. The meter should read less than 1 ohm. The resistance will typically be approximately 0.1-0.2 ohms. That low resistance is the resistance of the meter's wire leads. What's important is that it reads very low ohms. This tells you that the meter leads are intact. If you have defective leads (or a defective meter) and go straight to testing for voltage and the circuit you're dealing with is high voltage (mains voltage, 110+ volts), not knowing for certain that the meter is reliable could be lethal. For most instances in car amp repair, a bad lead simply means a lot of wasted time.
Text and Data:
If you're giving me part numbers, use upper case letters:
IRF3205 is much better than irf3205
If you're sending me a voltage/resistance/? meter reading and the display reads 0.345:
0.345 is much better than .345 or a partial reading like 0.34 or .34
Positive and Negative Readings:
The negative symbol () is very important. If the meter reads negative voltage, you need to include that. It will be assumed that all voltages are positive unless you make it very clear that they are negative. This simple omission can waste a huge amount of time. If you don't know what it looks like to have a negative reading, check the voltage across your 12v power supply with the meter probes properly oriented. Then reverse them and the meter will display a negative voltage (assuming that you're using a digital multimeter).
Model and PC#s for Amplifiers:
When you ask for help, you need to give the exact (EXACT) model number on the amplifier... NOT the model you think you remember. This prevents wasting time from the assumption that the amp is one model but it's actually an earlier or later model with virtually the same exact model number. Good quality photos of the main and any driver boards is also helpful.
Rockford has had a habit of stuffing the same board into more than one model amplifier. If your amp is a Rockford, send the PC# as well as the model number. Finding a diagram for a particular board number is more likely to be successful than looking for a diagram using a model number. Sample PC numbers for older amps, PC-****-*. For newer amps 1325-*****-**. The 2-digit suffix is the revision number and not generally critically important.
Meter Reference Point (contact point for black probe):
When measuring voltage, if you're measuring the voltage on the primary side of the power supply (the '12v' side), using the primary ground (the connection to the chassis ground of the vehicle) as the reference is perfectly fine. For this, you will typically place the black meter probe on the amplifier's main ground terminal.
When measuring the voltage on the secondary side (the audio side of the amplifier's switching power supply transformer) you need to confirm that the primary and secondary are connected, to some degree. The most common connection is a 1kΩ (1000 ohms) resistor between the primary ground (main ground terminal) and the secondary ground (transformer secondary center-tap or the non-bridging speaker terminals). If you measure 1000 ohms or less between the primary and secondary grounds, you can use the primary ground as the reference (placement for black meter probe) for your multimeter. If you read more than 1000 ohms between the primary and secondary grounds, use a secondary ground as the reference.
Not 100% reliable for more complex amplifiers. For basic amplifiers (virtually all class B or class AB amplifiers) there is only one secondary center-tap choice. It's the same as the secondary ground. For more complex amplifiers, it's common to have secondary windings in series. Amplifiers with this transformer configuration will have significant voltage on their center-tap windings. Instead of being a secondary ground, they are actually the output windings from the previous series-connected transformer. For multimeters, it makes no difference if you place your meter's ground probe on the 'hot' secondary center tap. For a mains-powered scope, it's a huge problem. This will be explained in excruciating detail on the Switching Power Supply Troubleshooting page. If this is the first time through the tutorial, continue below. If you've already read through this entire page, click HERE. Continuing to go on to item #39 of that page will be overwhelming for most rookie techs.
The non-bridging speaker terminals are highlighted by the red arrows in the image below. For this diagram, they use the BTL designation for bridging. The bridging terminals are the left positive and the right negative. As you can see by the heavy/thick black line connecting the other two terminals (the two terminals that are NOT used for bridging and the ones you would use as the secondary reference), they have a direct connection to each other and to ground (heavy black lines are typically ground). These lead back to the secondary ground. THIS is a partial diagram showing the heavy black ground lines back at the power transformer. These images were taken from the Sony XM-1004 service manual.
Initially, you can generally find the non-bridging terminals by finding 0 ohm continuity between the terminals but remember that the non-bridging terminals will be one of the positive speaker terminals and one of the negative speaker terminals of the amplifier. Confirm that those terminals also read 0 ohms to the secondary winding of the power transformer.
For the First of Many Times:
When troubleshooting, especially when you have very little experience, do as much work as possible with the heatsink-mounted components tightly clamped to the heatsink. This will greatly reduce the risk of component failure from overheating (which can sometimes happen within just a few seconds). The components referred to here are indicated below. Of course, those in the photo are not clamped to the heatsink and would be at risk of failing unless you were paying very close attention to their temperature (it's easy to get distracted and to forget to do this).
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
Trouble Getting Rock-Solid Numbers:
When you're measuring the voltage on a circuit, you may find that, if you go back to confirm the values you found the first time through, those numbers aren't precisely the same. That's to be expected and you will nearly always double-check voltages when they're being used for troubleshooting. Various components are temperature sensitive. When an amp is run for any length of time, the components change in temperature. You shouldn't rush when doing this but you should get the readings in a timely manner and (when possible) after the amp has had power applied for about a minute or so... and run back through the pins a second time to make sure you have the voltages correct.
Many times, is not the precise voltage but the voltage in relation to the voltage on another point in the circuit. If you're told to place the black probe on a given point/component terminal, it's likely important that you do as instructed. If it's not possible, ask for suggestions.
An example of this (^^^) is when told to measure the voltage on one of the power supply driver ICs and you're told to place the black probe on pin 7 but you figure that pin 7 is connected to ground so you'll just place the black probe there... well, not all grounds will be at the same voltage. If the voltage on pin 7 is a few thousandths of a volt from the ground pin and the voltages are critical, the voltage on pin 7 has to be subtracted from ALL of the voltages you give which is a huge pain in the... Not everything is as easy as clicking a 'like' button. Get used to it.
Too Much Too Soon?
There is a page that's here to help you learn about reference points when measuring voltage. If you're brand-new to multimeters and repair work, it may be more than you need/want to know at this point. If you want to give it a quick look, click HERE.
Just Don't!
Don't use the 'continuity' mode on your meter.
If you want to know more about using multimeters in general...
Most Working Technicians Don't Have Any Desire to be Teachers:
Be aware that most techs don't want to do tech support. You may find a few who will, on a limited basis, but be mindful that they are trying to run a business. Unless you're paying them for their time, they're likely just being polite when they answer the phone or an email regarding tech support. If they do try to help, offer to pay them for their time.
That doesn't apply to me. I'm retired and enjoy providing tech support to those who do what they can to make the process flow well the entire reason for this partitioned block.
If you're asked for a photo of the board (or anything else in the amp), don't send a blurry, poorly lit image (too dark, huge [make that any] flash/light flare in the photo...). Take pride in what you do and do your best, realizing that your best may be at the sharp end of a steep learning curve. Continue taking photos (that cost nothing) until you get a good quality image with the components of interest in good focus/lighting. If the extra 10 minutes it takes to get a good photo isn't worth the time, the amp evidently isn't worth repairing. After you learn how to take a good quality photo, it only takes seconds to get acceptable results.
You Have to Know... (items 1-5 below are monumentally important)
One of the first tasks you perform do when repairing an amp is to remove all defective components. While there will be sections that give you a guide on how to troubleshoot amp faults, none of those will do any good if you don't know the components, how they're supposed to work and how to test them. This page will help greatly on learning those components and what to check for. Don't just skim over the information.
The statement above is fairly generic but below are some specific items that you have to know to make electronics repair work easier (possible?). The knowledge you need to do this work isn't insignificant and acquiring what you need to know will take some real effort. Don't expect everything to be as simple as tapping a thumbs-up icon on a social media site (unless you have a 200+ I.Q.).
You can expect wasting many hours of your life if you attempt to do this work without learning the basics. The items in the following list likely won't mean anything to you at this point (they will seem like random words) but you will understand them (very well) as you diligently work through the tutorial. If it takes a week of doing nothing else but getting to fully understand the function of each the next individual items as you come to them, take that time.<IIt will save FAR more than that time in the future. Seriously, expect to flounder in vain if you fail to learn/do the following.
  1. The functioning of the switching power supply driver ICs (IC = Integrated Circuit = 'chip'). The most important is the TL494/TL594/KA7500 (all VERY similar). People who have been working at this for 10 years, or more, still haven't taken the time to understand this IC and waste more time and money replacing perfectly good ICs than you'd believe. It's as bad as replacing perfectly good capacitors, for no reason. This power supply driver IC has many different features but its response to the inputs on its pins is very predictable if you just take the time to learn how it works.
    Although you won't see it much in this tutorial, if you reference other technical websites or datasheets, you will see a switching power supply referred to as a DC-DC converter (or shortened to converter i.e. boost and flyback). The term converter is used because it takes DC voltage (12v in a vehicle) and converts it, ultimately, into one or more other DC voltages.
  2. The function of op-amps (operational amplifiers). These are used in virtually every amplifier. They can be confusing if you don't take the time to understand them. The basics are easy and the more complex characteristics like knowing the precise output with varying configurations and resistor combinations can be understood with a bit of study. The op-amp page of this tutorial has interactive demos to help you understand the op-amp in most configurations.
  3. This is one that I've just about given up on but it's such a wonderful thing that I keep trying. Using your mains-powered scope in differential mode... It's using two probes/channels (much like you do with your multimeter) of the scope to view a signal with more resolution than you can see, when using only one channel of your scope. It shows you the difference between two points in the circuit. This is somewhat easier for older analog scopes but if you know how to use your digital scope, it is easy to do.
  4. The use of DC coupling on the oscilloscope is another pointless battle that I will continue to fight. If you're trying to determine if drive signals are acceptable with your scope in AC coupling mode, you may as well be using a bleeping Etch-A-Sketch.
  5. Take notes and photos and keep them well organized. More on that, later on this page (and others).

I try not to be too repetitive in this tutorial but you'll see me repeatedly rant about the items above... not because I want to annoy you but because I want you to succeed. You'll also see this again... If you're honestly interested in this type of work, you need to read this material like you want to know it, not like it's punishment for something that you didn't do. Let's hope you read it more carefully/thoroughly than the yellow section at the top of this page (that, according to records, has never been read in its entirety << a battle that I've long since given up on).
Protect Your Assets (CYA):
If you have assets (home, cars, savings...) and want to protect them against possible lawsuits, you may want to form a company (either LLC or become incorporated). What I know about either could be written legibly on the head of a straight pin with a broad tip felt marker. There is plenty of information about this online. Use your preferred, modern browser. This is a topic that could be used by malicious sites to steal personal information and you want to protect yourself.
And again, if you're not using a signal source with a grounded shield (remember, only $10 in parts) and an intermittently shorted transformer causes a car fire (that could be parked in an attached garage), you'd better hope your A is well C'd by insurance and/or LLC protection.
Don't Void the Warranty:
If you're going to disassemble an amplifier, be warned that opening many amplifiers will void the warranty. If the amplifier is severely damaged, breaking the warranty stickers/seals may well cost the owner of the amplifier hundreds of dollars if it has to be sent back to the manufacturer (you'll be at their mercy). You first want to check to see if the amplifier actually has a problem. Many times, the problem is in the vehicle and the amplifier is just fine.
BEFORE opening the amplifier, ask the owner if it's under warranty. If it is, inform them that the warranty will be void if you open it. If it's supposed to be under warranty and the tamper-evident label/sticker is already broken, immediately show the owner so he knows that you didn't break the seal. This is only one advantage to talking with the owner when he is there to drop off the amp. Avoid problems before they become problems.
If you take in repairs via shipping/mail, include this type of information on the site so that your customers know what to expect. THIS is a link to a sample of what I used to have when I was taking in repairs. I'm sure that all of the forms are well out of date (some of this is from about 2009) but it may give you some ideas of what to include.
Amp Modification:
It seems that everyone wants to get more power out of their amps. This tutorial only includes modifications that resolve design flaws. There is no magic bullet when it comes to getting more power out of an amp. You have to change virtually everything to get any useful gains and even then, the heatsink may not allow anything more than short bursts at the higher power because it can't soak enough heat from the transistors. Using replacement transistors that are rated for higher power won't generally do anything to boost power output and may cause more problems that could require a re-engineering of the circuit.
The term transistor has been used but hasn't had a detailed description as of yet. That will come in time, but will have to be introduced in steps because there is no simple, comprehensive way to cover them. For now, understand that the transistors are the majority of the electronic devices that are tightly clamped to the heatsink and are the workhorses in an amplifier. They do virtually all of the hard work, pass all of the high-current and dissipate the most heat of any of the components in the amplifier. Below, the transistors are in the yellow rectangles. Of the other four devices clamped to the heatsink, two are voltage regulators and two are rectifiers.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
It's Easy to Destroy...:
...perfectly good semiconductors (transistors, rectifiers, regulators...) if the amplifier is powered up without having the semiconductors clamped tightly to the heatsink. Even with no speakers connected and no audio signal, an amplifier can fail catastrophically within seconds if the components that are normally heatsink mounted are not being cooled by the heatsink. This will be repeated elsewhere but this is VERY important and it's common to create MANY other problems because a component failed due to it overheating. This is a simple mistake that can be costly in replacement parts and labor (troubleshooting plus the time to replace the defective components). For those into sports, this would be considered an unforced error that cost the team the game.
A HUGE Mistake:
One case in point... I was working on an MTX amplifier and had removed the clamps from some of the components. I powered up the amplifier for a few seconds and a regulator transistor overheated and shorted. This happened very quickly. When the transistor shorted, it destroyed (explosively) several SMD (surface mount device) capacitors, both fans, several SMD semiconductors and several SMD resistors.
If it's not possible to work on a particular problem/fault with the amplifier in it's original heatsink, you can use a makeshift temporary heatsink that will keep the components relatively cool (at low power/idle).
Summing up the previous 2 paragraphs, take your time, pay attention to the temperature of components and follow suggestions offered in the tutorial. Keeping components clamped to the heatsink when testing is one of the most important. It may be time consuming but when you first start this type of work, simple mistakes can cause you to get discouraged. Don't let avoidable mistakes derail you.
Don't be Lazy/Ignorant:
Above, the term 'heatsink' was used. Many times, the term is shortened to 'sink' when referring to the heatsink. Do NOT use 'sync' as an abbreviated form of sink. It's an abbreviated form of synchronize. Those who are educated/experienced will consider you to be un-educated or worse, an idiot.
When asking for help, many of those who are trying to help will not help anyone who they feel are too stupid to warrant their time. I will generally try to correct those using incorrect terms (until it becomes obvious that someone is too lazy to try to make an effort to educate themselves). That said, I will refuse to help those who won't, at least, try to write properly (punctuation, capitalization, spelling).
Until you know an amplifier well, you should always have the semiconductors clamped to the sink when the amplifier is powered up and you should have either a current limiter or a relatively low-rated fuse (10-15 amp) in series with the B+ line. Having the semiconductors clamped to the sink keeps them from overheating. The low-rated fuse in the B+ line helps prevent excessive current flow if something is significantly wrong with the amp. Later, you'll see how low value resistors (in place of the low-rated fuse) are used to allow the amp to power up while preventing excessive current flow.
Preferred Fuses:
I use ATC/ATO fuses when I need to protect an amp with a fuse. ATM and ATM-LP may also be OK choices since they're very similar to the ATx fuses. Fuses like 5x20mm or AGC fuses may blow more easily than the ATx fuses, are more difficult to find and may not be, in any way, a good choice. Fuses like the MAXI or AGU of the same rating as the ATx fuses will typically take longer to blow and are much more expensive than the ATx fuses. If you stock them as replacements for blown/missing fuses in amplifiers, you can use them but go to the next lower fuse value than you'd use with the ATx fuses. THIS is a link to the Fuses page where you will find more information on all of these fuses, alternative fuses and fuse holders.
Reduce Number of Variables when Troubleshooting
This paragraph should not be necessary if you're thinking logically when troubleshooting an amp but it has happened so many times that it has to be included. When troubleshooting a problem and ESPECIALLY when asking for help troubleshooting a problem, you need to reduce the number of variables as much as possible.
One of the most annoying problems for me is when someone uses the amp's gain control to adjust the output of an amp instead of using the signal source's or some other inline volume control.
If you have a problem and email telling me that the amp shuts down or has some similar problem when you get the gain to x-position, expect a long delay for a reply... if you get one at all. Use a proper signal source (preferably a proper head unit) that has its ground connected to the same ground as the amplifier being tested and adjust the signal level with the volume control on the signal source.
When you adjust the level with the gain, you are introducing a second variable. The problem could be with the gain control or could be a problem that corresponds to a particular output level of the amp. If you think it's the gain control, set volume on the head unit to different levels. If the problem occurs at the same position on the gain control, the problem is likely due to a dirty or defective gain control. If the problem corresponds to the output level, that points to a different type of problem.
Potentiometer Based Level Controller:
THIS link is for a section of the Potentiometers page of the tutorial and shows how to use a potentiometer as a level controller. I've been using this type of volume control in the Bench Switcher that I built back in 2005. It's always at hand and you can adjust the volume much more quickly than you can with any digital volume control. The example shows a Radio Shack part (which is still available, in limited quantities, on eBay and elsewhere in 2025) but virtually any potentiometer of 10k-100k will work perfectly. A logarithmic taper is ideal but not imperative. It's not even a requirement that the pot be a dual element component. There's nothing that requires a stereo signal for testing amplifiers.
READ THE ABOVE SECTION UNTIL YOU CANNOT POSSIBLY FORGET IT
Taking Photos as a Backup Plan:
The next image may seem odd for an amp repair tutorial but it may be one of the most important tools you have. This tutorial is about much more than just the repair aspect. There will be many tips that I wish I'd have heard earlier in my time doing repairs. Most are more valuable (for someone who will do this for more than a couple of weeks/months) than you can imagine.
When working on amplifiers, there will be times when components fail and that failure causes one or more parts to burn to a point where all markings are destroyed. This can be a problem when the manufacturer can't or won't tell you the value of the component or when the service manual/schematic diagram isn't available.
Most people won't use a camera and will refuse to use anything other than their beloved phones. Some phones can take photos as good as a camera but, even an old inexpensive camera like the one above, can get photo after photo effortlessly. This is a 20 year old<I2MP camera and it takes wonderful macro photos. Not many of these are left but newer Nikon CoolPix cameras can do an even better job... again, effortlessly. Ask around, you will likely find people who will give you (or sell cheaply) an old camera they have laying around. Get yourself a good set of rechargeable AA batteries (likely what the old camera will use) and a charger. I used Eneloop batteries and the Eneloop Pro were the best AA rechargeables I'd ever used. Check Battery Junction for reviews on batteries.
THIS link is to the photography section of the basic repair page online. It's likely that you've already seen it but you may want to read it again. THIS is a link to my macro-photography page and goes deeper into taking photos of small objects.
Organization is Key:
Don't discard the photos that you take. Start a folder with sub folders that have the amp make, then the individual models. The Rockford T1500 is an extreme but shows that a lot of data (200+ total files in 15 folders) is collected for some models.
Be Thorough:
When you take photos, be sure to take photos of the faces/part numbers of the original heatsink mounted components. Also take photos of the electrolytic capacitors in the amp... from the side showing their voltage rating, their value and whether they're 85C or 105C caps. This is something I failed to do, far too often. Many times amps are second-hand repairs and the parts are missing or could possibly be the wrong parts. If the manufacturer won't help, your photos of an identical make/model amp's components may be your only reliable source for the part numbers.
After taking the photos, look through them on your computer (or anything with a good monitor). Look at the various resistors (and other small components) to confirm that the photos are of sufficient quality to allow you to read the markings clearly. Don't just look at the center of the photo (where it's likely to be in focus). Make sure that the camera didn't focus on the top of a tall capacitor or transformer, leaving the resistors and such out of focus. THIS is a better photo of the area with the resistors in focus. Check the quality of the entire image. Also know that the parts that you feel are unimportant are, many times, the ones you need to ID so get photos of everything. There will be small, low-profile components that will obscured by larger components. Take photos from enough angles, move wires out of the way... to capture everything. The original photos of the reduced images above can be found in the JL 500/1 rev10 folder:
miscellaneousstuff/jlaudio/jlaudio500/jl 500 rev10/
Resolution:
Save the files at a reasonable resolution. You don't want files that will unnecessarily take up drive space. Adjust and remember the resolution you use for the best cost/benefit ratio (regarding storage space). Not only do you take up space with excessive file sizes, it takes longer to process them (building thumbnail databases, scrolling through images quickly...).
Start with this as a suggestion and adjust to suit your needs. Take the photos so that you can easily read the component values (markings on all SMD components and all resistors) at about 3/4 of the full size. It's easy to pull back to 75% in Irfanview and likely in other graphics software.
The photos of amps should be taken before you begin repairs. Sometimes, a part goes up in flames when you apply power. That can also happen after you replace a part that restores current flow to parts of the circuit that previously had none. Taking photos of the finished product is also good, especially if you replaced parts that were parts burned beyond recognition or obscured by soot.
Optional Photos:
Although the previous paragraph focused on internal electronic components, there may be a few other items you may want to photograph. I had one 'collector' complain that I installed the bottom cover backwards (model/information/serial number label was on the wrong end of the amp). I did but it was insignificant... to me.. but not to him. I did THIS more times than I like admitting. Fortunately, the labels saved me. Taking a few overall photos of an amp before you start disassembling it may prove useful.
Internally, there are a couple of features that you may want to photograph. The first is the transistor clips/clamps. In some instances, they will only fit properly in the original configuration but can be installed with other configurations. If you perform enough repairs, you'll see quite a few amps with numbers on the clamps. I've numbered clamps and even marked heatsinks for clamps that would be difficult to mark but photographing is a cleaner way to do it.
The screws are another item. There will be instances where screws that look different (chrome/dull gray/black) will be used in the same numbers and will fit in various locations. Again, some people get upset if their amps are not exactly the same (physically) when returned to them. I know, they shouldn't be going back into it but some will. Some people have spent hours looking at their beloved amps and are finicky about slight changes. Some will consider the amp improperly reassembled if it's not precisely the same.
You can use Tamper Evident labels and tell them that the warranty will be void if the labels are removed but I'm not sure if you can legally void the warranty if they do break the seals. I doubt that many people would take you to court but with social media, they may be able to damage your reputation.
Cost of Storage:
Digital photos cost nearly nothing, now that storage drives are dirt-cheap ($35 for an SSD drive that will hold more photos than you're likely to ever take). Save to one drive and backup all files to a second drive at least once a month. Keep the second backup in a different location than the first, in case of fire or theft. If you lose one copy of the files, back it up immediately. If you can justify the cost of (private) cloud storage, that may be an option for the backup. You want at least one copy of the photos stored locally because (if you're like me), you'll reference them regularly and local access is MUCH faster than with cloud-based storage. It also give you options for the image viewer (Irfanview, recommended).
Connection to Backup Drives:
My preferred backup storage is a SATA SSD drive. The main storage drive is plugged into a SATA port on my motherboard. To connect externally to a backup drive, I have two options, either a USB to SATA cloning cable or a docking station. Plugged into USB 3.0 (the fastest I have), the transfers are fast. You can backup to a USB flash drive but they can be unreliable and slow.
It may be difficult to, initially, justify the cost of storing the images but I have been taking/collecting photos... for 20+ years and a cost of less than $100 is a bargain to protect all of those photos... not to mention the great resource they are in finding the values of burned/missing parts. The backups are also for all of the service literature (diagrams, service manuals, etc.) I've collected over the years, much of which may no longer be available.
Storage of Notes Alone:
While photo storage is very important, the storage of notes (particularly of voltages taken from the various circuit points in a working amplifier), is important because they are a valuable resource. This means that they should be protected, as well. These take up virtually no space in text format (best format because it allows them to be easily edited) but even as a photo/scan produced from a handwritten page, they don't require a lot of storage space. If you don't have a secondary storage drive (an inexpensive [Wal-mart, less than $10] USB drive is perfectly suitable), send the notes to yourself in an email and make a dedicated folder in your email account in which to save the note files. Some may choose to store files in their phones but unless you have the phone sync'd with a cloud storage, I wouldn't recommend it since phones get lost/stolen and you wouldn't want to lose the files.
Take Notes:
This can make the difference between success and failure. Well taken notes let you to make a reference for yourself that you may not be able to get from any other source. Follow the links for note taking each time you see them. Good records and reference information can make the difference between making money or losing money for many repairs.
In addition to taking photos, record various characteristics like the idle current. This isn't, necessarily, just for an amp you're repairing. This can be taken from amps known to be in good working condition (you'll be asked to bench-test amps to see if they're working before being installed by a car audio shop. Having this information (and any other information that you record) can help determine if there is a problem with the various drive circuits.
This may or not be viable for everyone reading this but most cell phones can convert voice to text. If you don't want to take the time to write anything down, use the voice to text feature on your phone and send the text messages to your computer. Then move them to the appropriate folder on your computer. Don't store everything on your phone. They get lost or stolen and you don't want to lose (possibly) years worth of valuable data.
On many amps, there is an initial idle current (power supply operating only) then a jump in idle current as the bias circuit is engaged (class B, AB... amps, can commonly be seen in Rockford amps). For switching amps (class D...), when the output stage is enabled (the output transistors begin driving a square wave rail-rail), there is also an increase in idle current. You'll see more encouragements and suggestions for taking notes throughout the tutorial.
It may also be helpful to note if any components operate at high temperatures. Large resistors will almost always run hot at idle (not referring to the emitter/source resistors which are large but almost always run cool at idle). Inductors will run hot in some (most) amps. In many amps, they idle at such high temperatures that you cannot hold your finger on them for more than a second (unless you're a welder, by trade). The components that you're most likely to note are integrated circuits running hot.
Amps That Fix Themselves...
Amps that fix themselves are just as likely to UN-fix themselves. If you receive an amp for repair that has a problem and the problem miraculously resolves itself, do NOT consider that amp repaired. Intermittent problems are common. Many times, there will be an intermittent short or an intermittently open connection that will temporarily disappear and no matter how you stress the board (flexing/tapping..), you won't be able to make the fault return. If you charge owner for repairing the amp, EXPECT the amp to come back. If you tell the owner that the problem is intermittent and that you're not 100% sure that you found it, it will be better than if you tell him it's definitively repaired.
If you let customers know that there may be a problem and that you'll cover it (repair it for no additional charge), they're more likely to be understanding. You should, however, explain to them that you will not cover additional damage if the amp is improperly installed. The alternative to this (and better in my opinion) is not to charge for the repair. When you do something that should not solve a problem and it does (replacing parts that checked OK after you removed them), you should suspect that it's a coincidence and something else changed as well.
One example of a power supply that may have an intermittent short:
While the amp is powering up normally, twist/push/pull on the transformer and inductor (if it has one) to see if the current draw changes. Shorted transformers and inductors can (and do) cause intermittent problems. Windings can short to other windings, to the circuit board and to adjacent components. When stressing the transformer, it's best to power the amp up through a current limiter. For amps that won't power up through a current limiter, use a low-rated fuse. A 7.5 amp fuse will typically work for small amps. Except for really high powered amps, you shouldn't need more than a 15 or 20 amp fuse. Use the lowest value that you can to offer the best protection for the power supply FETs.
The twisting/pushing/pulling test will be used often (ideally, several times on every amp from the time it's first back to functioning and again just before the top/bottom cover is installed). Don't forget it. It can save valuable time and prevent embarrassing boomerang amplifier repairs. See TT5, item #1 for more on this.
As a side note, one problem with using current limiters (which are very useful) is that some amps will never power up from a power supply that has current limiting below about 15 amps. There have been requests for help from too many people using a 3 or 5 amp supply that have wasted many hours troubleshooting a problem that didn't exist. Item #6 on the Equipment page has more on using a current limiter.
Rail Voltage:
In general, when you see the term rail voltage, it's a voltage (or pair of voltages, ±) produced by the amplifier's switching power supply (the part with the large toroidal, wire-wound transformer). This is (generally) the source of power for the output transistors. The output transistors drive voltage/power to the speakers. In most amplifiers, this rail voltage is the greatest voltage (positive and negative) and can produce the highest current of all of the voltages generated by the power supply.
For the majority of amplifiers, the rail voltage will have positive and negative components (above and below ground/0v). For some amplifiers, like those in many class D amplifiers, there will only be a positive rail voltage for the output transistors. There will likely be ±supply voltage for the preamp components but only positive rail voltage for the output transistors.
This (the use of toroidal [doughnut shaped] transformers), like so many things, is not absolute. Many transformers used by Japanese, Brazilian and even American manufactures (like Zapco) are square transformers (cheaper to produce in large numbers).
'Generally' because you can use the term for voltages other than the main (output) supply rails. For example, you may see the term ±15v rails. This would be the regulated, low-voltage supply that's typically used for the various preamp-level components.
Yet another set of rails... The ±15v voltage regulators may have their own set of rails at approximately ±20-25v. These are often produced because the voltage regulators often have a limit to their acceptable input voltage so their input can't be taken from the full output transistor rail voltage. The lower voltage rails are often produced by a dedicated set of windings on the power transformer.
In some amplifiers, there is a low-current, higher_than_rail driver voltage that's produced that's approximately 10-15v above the main rail voltage. This allows the output transistors to be driven more efficiently (delivering closer to 100% of the rail voltage). In those amplifiers, the driver voltage would technically be greater than the main rail voltage.
Warning!!
There will be amps that have a fault that causes it to drive significant (well over 1v) DC voltage to the speaker. This isn't simple DC offset, especially when rail voltage (30, 40, 50v, or more) is driven to the speaker. This can be a fire hazard and can destroy expensive speaker(s) connected to the faulty channel. If the fault is intermittent, the amp cannot be used until positively repaired. If you have to repair it, be absolutely sure that you find the intermittent problem.
The same applies to an intermittently shorted transformer that's driving B+ (12v) to the RCA shields. You were warned about this previously on this page in the note about grounded shields (which was entirely ignored/dismissed). If you refuse to make and use the simple adapter, you had better have plenty of insurance, an LLC or both.
If you can't definitively find the fault, do not accept payment for repair. Tell the owner that it's not repaired and would be dangerous to use it as it is. This is critically important if you want to limit liability. If the problem reoccurs and destroys speakers or causes a fire, you could be held liable. Find the fault or return it to the owner at no charge. If you charged a deposit, return that as well. You want to make sure that the owner can't say that he paid you to do anything and that what you were paid for resulted in any type of loss. People are litigious (some, enthusiastically so). Don't give them a chance to think to themselves... ka-ching (or is it, cha-ching) for anything you do.
Repairing Amplifiers for Amp 'Collectors':
When repairing amplifiers, and more specifically older/vintage amplifiers, you need to determine if the owner is a 'collector' or someone who simply likes older amplifiers. The two are very different. A collector will likely know every scratch/dent/ding on the amp. They may even be aware of all minor defects on the inside of the amp. While you always want to take care not to do any damage to an amplifier, you have to be especially careful with amplifiers for amp collectors. Sometimes, when repairing an amp, you may allow the barrel of the soldering iron touch a wire or some other component with a relatively low melting point (like the plastic casing for the capacitor below). For a standard repair, this may be absolutely insignificant but if it happens when working on a collectable amp, it could be a significant mistake. Part of the value of the amp may be that all of the wiring is original and in perfect condition. If you accidentally melt one of the wires (striped wire used in vintage Orion amps) and an exact replacement isn't available (short of buying an identical amp to salvage the damaged parts from), you may have problems when the owner comes to pick it up.
What Type of Work do they Expect You to do?
Something else that you need to discuss with collectors is the level of repair. Do they want you to undo all previous repairs that don't look original. This could include replacing resistors that are not the same size or physical appearance of the original parts. You also need to determine if they want a repair or a complete refurb. A repair would get it back to good working order. A refurbishment may include replacement of ALL of the electrolytic capacitors and ALL of the heatsink mounted semiconductors. A complete refurbishment may take a full day or more where a repair may only take an hour or so. You need to know what they expect to quote the price accurately.
Move Carefully:
When working on amps, you'll likely have lots of wires connected to the amp. Since it's not really practical to have all of the wires cut to the shortest length possible (because many have to work with multiple amp models), it's easy to become entangled in the wires (they can even get caught in the chair and will be pulled when the chair is rotated). If this happens and you get up to go get a part or look up a datasheet (or for any other reason), you must be extremely careful not to pull the amp off of the bench. Doing so can do extensive damage. When getting up, do so slowly and make sure that you are clear of all wires before walking away. If the work-surface is more rubbery than slick (laminated countertop material...), this is less likely to happen but the rubbery surface won't eliminate the risk of pulling items off of the bench.
In a similar way, I've seen people disconnect an amp (or so they thought) and when they begin to walk away, the amp is nearly pulled out of their hands or something is pulled off of the bench when the wires (that they 'thought' were disconnected) tighten up. Again, Be careful and take your time. This may seem obvious but when you're deep-in-thought, learning something new and you're distracted, it's easy to make simple mistakes.
Irreplaceable Parts:
Some of the older, valuable, collector's item types of amps had knobs that could be (accidentally) pushed back into the face of the amp, breaking the potentiometers. Since these old potentiometers are well out of production and virtually impossible to find (if they need to be replaced), it's imperative that you not break them.
Below, one knob has a shoulder and the other does not. The ones without the shoulder are the type that can cause problems. When you get an amp that could have an issue with the knobs breaking the potentiometers, remove the knobs immediately and keep them attached to the bottom cover or heatsink of the amp. The knobs are nearly as hard to find as the pots so you do NOT want to lose them.
Do not use tape to attach the knobs to outside of the bottom cover. The paint is often on the verge of peeling off and tape can pull it off. Even the blue painter's masking tape will stick aggressively if left in place for a long period of time. If this is for a collector, he will NOT be amused if the paint and/or markings are damaged.
Put the knobs/accessories in a Ziploc type bag and use a piece of string/wire/zip-tie to attach the bag to one of the mounting holes in the cover or to a screw that's screwed into the end of the heatsink all but about 1/8". If a significant length of screw extends from the heatsink, it could easily be broken off and could be difficult to remove. If the amp has to be shipped back to the owner, protect the knobs or leave them in the bag and let the owner reinstall them.
If you don't keep the knobs (or any accessories) attached to the amp, make a note (that cannot be lost) of the 'safe place' where you put them and what the container looks like. I've put hundreds of items in a safe place... and forgot what/where that safe place was. With my luck, when I finally find that place, I'll also find Jimmy Hoffa.
3D Printed Parts:
Everyone knows that parts can be printed in 3D but, for the most part, the parts are not printed with a perfectly smooth finish if printed by a desktop printer. Higher quality parts can be produced but it typically takes a much more sophisticated print process. This can be done by internet printers (in either plastic or metal). The replacement parts will have to either be modeled by you or scanned into the computer by a laser scanner. This is doable but can be expensive.
Just to Confirm...
You did read EVERYTHING in the yellow table at the top of the page, didn't you? If not, you WILL miss out on some of the features and content. It will take just a minute or two to read it. For example, what do you do when you click on a link and the landing point on that page isn't what you expected? Generally, people close the new tab/window and let themselves believe that clicking the link was pointless or a mistake. A mistake, possible (some links are broken because content was moved to a more appropriate location), but done for no reason, not likely. If you find such a link, email me.
babin_perry@yahoo.com
Take Your Time:
Although some people are better at this type of work than others, virtually anyone can learn to do repair work. If you have no experience with this type of work, when you open the first amplifier, it will look completely foreign to you. It's unlikely that you'll know what any of the parts are and if you know what they are, it's unlikely that you'll know what they do. That's to be expected. Although there is a lot to learn, it's really not too difficult. If you don't remember/absorb everything the first time you read it, it may be discouraging but that's also to be expected. Each time you read through it, you'll pick up more and more information. If you perform a few repairs and re-read part of the tutorial, more points/concepts will begin to make sense. Keep in mind that this tutorial contains VERY little irrelevant information. Virtually everything here is important. I'll suggest that you read through the entire tutorial once BEFORE you attempt the first repair. This will let you know precisely what information is provided. Then, when you begin to work on the first few pieces, you can refer back to the relevant sections.
Note:
If you read this page carefully and follow the links provided, it should take you at least several hours to cover this information. If you want to run through it quickly and then, at a later time return and read it thoroughly, thats OK. If you're new to electronics and repair work, I strongly recommend that you take your time.
Before Installing New Parts:
When initially troubleshooting, you will often do the absolute minimum to get the amp to function at the most basic level. This allows you to determine the severity of damage to the amplifier. When doing this, you will often use as many of the original parts as possible, generally removing only the ones that are preventing the amplifier from functioning and replacing a minimum number of parts to get the amp up and running. When doing this, it's common practice to use parts that survived from other repairs (that had to be replaced so you could have matching parts in the final repair of a previous amplifier). This is covered in a bit more detail on the Class D - Type 1 page. Read THIS section (in the cordoned area) and return. There is much you need to know before you can understand what's on the rest of that page.
This will be repeated throughout the tutorial but you will have instances where you have parallel components that have to share the load equally. This is where you need components that have matched characteristics. You won't typically need to do anything more than to use components that are from the same production batch (have matching date codes).
Problems After Installing New Parts:
There will be times where you find a significant number of defective parts and install their replacements and the amp won't power up. Too many people just start pulling all of the new parts to recheck various components/circuits (possibly some that were dismissed as OK, previously). If this happens, try to find a way to disable various sections of the amp to see if you can get the amp to power up, in part, without having to waste hours removing parts, clearing vias and reinstalling parts. Email me if you need help with this sort of problem.
babin_perry@yahoo.com
Have a Good, Logical Reason for Most Everything You Do:
To expand a bit on the statement above... Too many people, for some unknown reason, feel the need to remove all of the power semiconductors (those clamped to the heatsink) to check them. For virtually 100% of the times when an FET fails, it will be obvious in the board (0 ohms between at least two of their terminals). It's possible/common for all of the power supply FETs to fail but, except for very large amplifiers with large capacitor banks, output FETs typically only fail one or two at a time. Check them in the board and when you find one that has suspect readings, pull it alone. If you have questions (before you waste time pulling a dozen or more FETs), email me.
Some of the items in the next diagram will be unfamiliar but you can understand the basics. The center-tapped rectifiers (like the MUR1620CT) will appear to be shorted between their outer terminals. That's the transformer that's making them look shorted. The fine white line shows the current path that your meter reads when checking the diodes in the circuit. If the center-tapped rectifiers are not reading 0 ohms to the center terminal, there is no need to pull them for checking out of the circuit.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
Mistakes, Smoke and Fire:
I know you won't like this but... If you're like virtually every other person who has learned to do this type of work, you will make mistakes. Repeat, YOU WILL MAKE MISTAKES. You WILL short out components with your meter probes. You WILL install parts the wrong way (backwards). You WILL remove parts and forget where they go. All of these mistakes will lead to the destruction of parts and will be a gut-punch to your ego. It's not the end of the world when you make a mistake (but it will be annoying).
When parts start to fail in a dramatic way (smoke, fire, tiny explosions), DON'T panic. Calmly remove power from the amplifier and assess the damage. If someone says that they've never damaged any parts doing this type of work, you can be sure that they're either a liar or haven't done much repair work. With experience, you'll be less likely to destroy otherwise perfectly good parts. When you set up your work bench, use a quick-disconnect like the one shown under TT5, item #23.
Browser Issues and Missing Images
The next image shows how you can tell if Flash is working. The first image below (on the left) is what the next section should look like and the second image (on the right) is what some browsers will show. If this happens when using the suggested browsers, email me at:
babin_perry@yahoo.com
Flash Working Normally Flash Failed
Amplifier Current Draw:
You'll see the phrase 'excessive current draw' used often. It means that an amplifier is drawing more current from the 12v DC power source than it should (generally at idle, no load and no input signal). For most small to medium sized amplifiers, the current draw at idle is 0.5-2 amps. For larger amplifiers, the current draw can be as high as 5 amps at idle. Of course, when you connect a load (speaker) to the amplifier and drive signal into it, the current draw will increase as the amplifier produces power into the load. If you power up an amplifier and the amp meter on your 12v power supply swings to the maximum current and doesn't IMMEDIATELY fall back to approximately 1-2 amps of current (for small to medium sized amplifiers), the amplifier is drawing excessive current and you should not apply power again unless you do so through a current limiter (to be covered later) or until you find and repair the fault that's causing the excessive current draw. It's important that you are able to quickly switch off (or disconnect) the 12v power supply if there is a problem.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
In the above demo, the current draw only becomes excessive after remote voltage is applied. This is indicative of (most commonly) shorted audio output transistors but can also be due to a shorted rectifier, transformer or maybe even stray wire strands that have fallen into the amplifier. If the amp draws excessive current before remote voltage is applied and the power wires haven't been inadvertently connected with reverse polarity (backwards), you'd immediately disconnect the amp from the power supply and pull the cover on the amp to begin troubleshooting. If an amp's power supply connections are connected with reverse polarity, it can sometimes damage internal components. If you do this and you're lucky (or have the proper protections in place on your bench), it may not do any damage and making the proper power connections will allow you to continue testing.
When an amp is drawing excessive current, the power semiconductor components that are normally clamped to the heatsink can heat up very quickly and can fail within a few seconds. That's why you must carefully monitor the current draw of an amplifier if you don't know for a fact that it's in good working order. It's important that you always have the heatsink-mounted components clamped tightly to the heatsink when testing an amp if you don't know if it's working properly. Even if it is working properly, when testing the amp at anything more than minimal power output (with all protection devices, current limiters, etc... to be shown later) in place, you should have the heatsink mounted components clamped.
It's important that you always have the heatsink-mounted components clamped tightly to the heatsink when testing an amp if you don't know if it's working properly. << I know it's odd to dagger a sentence then simply repeat it but this sentence is just that important and for those who are doing nothing but skimming this (exceedingly important) page, maybe they will read at least one iteration of the sentence. It's a bit like the repeated warnings not to buy replacement semiconductors from eBay/Amazon.
In the following image, it may appear that the un-clamped transistors are against the heatsink and could transfer heat to the heatsink but that's not the case. When the clamp was removed, the transistors lifted just slightly and would overheat quickly. In a situation like this, if these transistors would fail (these are the output transistors), it would stress the power supply and could cause it the power supply FETs to fail catastrophically. In an amp like this (Power Acoustik A3000DB), this mistake could require that you replace nearly 50 parts (16 PS FETs, 16 gate resistors, 10 audio output transistors, driver transistors...). Take the time to clamp the transistors when the amp is powered up until you're experienced enough to know precisely what to expect. And... don't make the mistake of starving your amp for current.
Starting with Appropriate Amplifiers:
I always suggest that newbies begin with the simplest of amplifiers. The simplest amplifiers are typically the budget, class B (to be covered later) Asian amplifiers (from China and Korea). They generally have simple problems and they don't destroy a significant number of parts when they fail (generally). I would strongly suggest against starting with many of the American brands (particularly those that use surface mount components). Amplifiers like those from JL, MTX and Rockford can be difficult to repair. They are very good amplifiers but are much more complex than the cheap stuff. If your first repair attempts require that you repair complex problems in complex amplifiers, you'll get discouraged and will most surely be doomed to failure as a service/repair technician. If you start with the amplifiers that I suggest, you will build your confidence and have a much better chance of succeeding in this business. Even if you are an extremely intelligent person, this still applies to you. There's no point in making this business harder than it has to be.
Reality Check:
  • This has happened so many times... Seriously. People start with an 8000 watt amplifier (Taramps MD 8000.1 is VERY common) and have only a 20 amp supply to test it. These are often people have yet to master soldering/desoldering and don't have the proper tools to do the work. Ask yourself these questions if you're thinking that you can properly test really large amplifiers. If you don't test it as it should be, and it fails when the owner reinstalls it, will you know if you missed something or if the owner caused it to fail again?
  • How on Earth are you going to properly test an amp (to full power) that can draw 800 amps of current? The MD 8000.1 was over 900 amps on the YouTube dyno run.
  • Even an 8D battery (full datasheet) would not be able to supply enough current at the rated voltage (at least 12.6v) to test that amplifier properly.
  • Are you willing to spend the money ($thousands) for a proper mains powered supply to test an 8000w amplifier for more than a few seconds?
  • Do you even have the electrical supply in your shop to supply approximately 60 amps at 220v to that mains-powered power supply?
  • What are you going to use as a load that can take full power from the amplifier for more than a few seconds?
  • As another example with a much smaller amplifier, the amp two images below is the 500/1. The 1000/1 won't start reliably on my mains powered supplies. I must use an external battery for it to start reliably and to test at anywhere near full power, even though the mains supplies are well rated for the full power current draw of the 1000. JL amplifiers, in general, are not good as starter amplifiers.
  • This will be repeated but you should buy some cheap, simple, broken amplifiers (pawn shops, audio sales/installations shops...) to hone basic skills. Too many try to win a marathon before they learn to crawl. Don't be one of that group.
In the words of one of history's greatest philosophers: I'm pullin' for you. We’re all in this together.
Another reason to start with small, simple amplifiers is that you will destroy far fewer parts when you make a mistake or fail to find all of the problems before you apply power to it. Replacing the damaged parts will be much less expensive and much less time consuming. For example, if you're working on a small (50Wx2) amplifier and you make a mistake, you'll likely have replace no more than 4 transistors. The total time to replace them is likely less than 5 minutes. If you make a mistake on an amplifier like a Rockford 800a2 (which has the transistors soldered to the insulators), the time to replace the parts will be closer to an hour. The parts will be more expensive and there will be many more to replace.
The first image below is the type of amplifier you want to begin with (Bazooka EL1500). There are MANY different amplifiers of similar complexity that make good amplifiers on which to learn. The one after it (JL500/1) is NOT something you want as your first repair. Although the repairs on the JL can be simple, they often require significant knowledge to repair them. For example, the first amp has a single power supply that is the source of all power for the audio section. The JL has three (3) independent switching power supplies. Two are used when the amplifier is in operation. The third runs only in 'signal detect' mode. The Bazooka uses simple through-hole parts that are easy to deal with. Through-hole parts have wire terminal leads that are inserted into holes, from the top (component side) of the board. The leads are soldered on the bottom (solder side) of the board.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
The JL uses mostly surface mount (no wire/through-hole leads) components. Most of which are only 0.050" x 0.080". Some of the SMD resistors are only 2/3 the thickness of a US dime (0.33" vs 0.50"). If you try and fail to repair several complex amplifiers, you'll likely give up... believing that you're incapable of doing the work. If you start with appropriate amplifiers and you learn what's in this tutorial, you will VERY likely succeed. There are more photos of these amps in their respective folders in the miscellaneousstuff folder of this tutorial. If you're not using the Safari browser, click HERE to find the best way to access that folder. If using Safari, you can access the miscellaneousstuff folder directly/properly.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
Read down through the Notes/Review section at that link. It shows you the differences in what you see with Safari vs what you will see with other browsers.
Far too many people refuse to use the Safari browser but it's absolutely the best option for the tutorial (especially when Irfanview and PDF Xchange Viewer are installed). It opens the Windows file manager when you click on a folder link and allows easy browsing of those files. Other browsers (unless you're using an old version of Internet Explorer) just provide a page with individual links. Not all links to folders are critical information but are generally provided because they can be useful. If you're not usiung Safari because you had trouble installing it, email me.
babin_perry@yahoo.com
Don't be a Parts-Changer... Please
One thing that all competent technicians know is that it takes a lot of work/effort to become truly competent. Some people are driven to become competent and for those people, it's not a chore. Others who get there may have to force themselves to do what's required... but they get there. The last group may seem competent to those who don't know the business. To truly competent techs, an incompetent tech shows their ignorance the instant they open their mouths.
I don't know if you've ever heard the term 'parts-changer' but it's most certainly not complementary. When repairing ANYthing, you are much better off if you understand its operation well. To do that, you have to understand its components and how they work together. Without that, you're going to be a parts-changer, at best. You will never get the respect of anyone who knows what they're doing if that's all you are.
Take the time to understand the components and the general operation of the amp you're repairing and logically follow the circuit to find the faults. Don't think you have to know every component, every circuit, every amplifier before you start. You start with the basics (plenty of that in the tutorial) and learn new devices/circuits as needed. Only rarely should you hit a point where you have to guess at what's wrong. Working logically will get you, either to the exact defective components or to a small group of components that you need to check. Don't be satisfied with only being a parts-changer.
One thing that makes doing this work more difficult is a lack of technical documents and schematic diagrams. It's generally easy (not always free) to get service manuals for Japanese amps and for older Rockford amps. For many others, you have to be satisfied with 'close enough'. Fortunately, there are MANY clone type amps so it's possible for a schematic diagram that IS available to be useful for many other amps. More on this, as well as some sources for service manuals and schematic diagrams can be found on the TT4 page, item #7.
The Generic Class D - Type 1 is relatively common and service manuals like those for the JBL BP1200.1 can be helpful for many amplifiers. THIS is a short list of type 1 amplifiers.
Please put forth the effort to become a genuinely competent technician. It says a lot about your character in general when you are what you claim to be instead of simply frontin' (slang for putting up a false front, being a fake).
Tolerances:
Before we get to the common components section, the concept of 'tolerances' should be mentioned. When anything technical is manufactured, whether it's a piece of machined metal, a special rubber compound or an electronic component, that component is designed to have certain specifications. Since it's essentially impossible to have all produced components absolutely, precisely the same, there will be variations. Generally, there is a range of variations (often determined by it's use in the final assembly) in the component that are acceptable for that particular component. The acceptable range of variations are referred to as tolerances. For most components, the tolerances are stated by giving the marked specification plus or minus a percent of that specification. For example, ±1% or ±5%. In electronic repair, you will replace components with equal or better tolerances of the original.
Datasheets, in General:
Datasheets are important documents that you will use to identify various electronic components that you'll encounter. More than 800, for the most commonly used components, are included in the Semiconductor Datasheets folder. Datasheets are published by the manufacturers of the components and give virtually anything and everything you could possibly need to know about that component. They can vary from a one page document to a ridiculous 500+ page document for a microcontroller. Fortunately, most datasheets are no longer than 20 or 30 pages and the relevant information is near the top of the document, on only 3 or 4 pages.
Specifications on Distributor Websites:
Distributors (even reputable distributors) are not infallible. There will be times when you see specifications for a component and it appears that one component (with the same essential part number, just a different prefix/suffix) has significantly different specs (current rating is commonly wrong). For those parts, open both datasheets and look carefully at the specification and all parameters.
One common specification that changes is the current rating for two different temperature extremes. As an example, the continuous current rating for an FET (given in the datasheet for the IRF3205 click to open) may be 110 amps at 25°C and only 80 amps at 100°C (virtually all electronics are derated as their temperature increases). When the distributor was filling in values for current, one may have chosen the 25°C value and the other the 100°C value. When you open the two datasheets, you can compare the two matching specifications.
Derating is mentioned above. When looking at the various datasheets, you'll see that virtually all graphs showing the characteristics of a component are given as a curve. This is especially true for temperature-related specs.
For that FET, there are notes about the silicon current capacity and the package current capacity. The silicon rating is good information for quick surges but the package has to be able to pass the current and may not be able to pass the full silicon value continuously. As a side note, the silicon value is short term only because the thermal conductivity from the silicon isn't infinite so the silicon will heat relatively quickly and lose current capacity.
Specifications and Terminology on Competitor's Datasheets:
Comparing specs on datasheets from one specific manufacturer is an apples-to-apples proposition. It's not always so straightforward when comparing component specs from competitors. The differences in testing procedures and terminology can lead to confusion. This is to be expected and sometimes, you have to (sort of) read between the lines to understand the differences.
Common Amplifier Components
Below is a list of the most commonly used electronic parts that you'll find in an amplifier. In most of the descriptions, you will find a link to a different page in the tutorial. They will give you more information on the components. Most pages will have photos to let you see samples of each component. If you're trying to rush through this tutorial (not good <<seriously, not good), spend at least 60 seconds on each of the linked pages for each component below. Even in that short time, you'll likely learn something new about that particular component.
~~~~~~~~~~~~~~~~~~~~~ End of Common Amplifier Components ~~~~~~~~~~~~~~~~~~~~~
Measuring and Recording Values:
What immediately follows isn't intended to be an introduction to troubleshooting. It's a common scenario.
Several points above mentioned measuring voltage, resistance, etc... After looking for any obvious physical damage, the first troubleshooting you'll do on an amplifier that won't power up fully is to measure voltage. Then, if voltage is missing at a certain critical point (power supply terminals of the switch-mode driver IC...), you will trace the circuit between the points where voltage is present and correct (possibly back to the B+ and remote turn-on terminals) and where the voltage is notably absent to find where it's being lost (due to an open trace, resistor, transistor...).
This is still a very early point in the tutorial (only the second page in the order it's intended to be read)<Iso you haven't learned what voltages should be present at various circuit points and on the pins of the most common ICs. Not to get too far ahead of ourselves, but, in general you will start with the primary side of the power supply and the switch-mode driver IC and work from there. Without this IC functioning, the entire audio section is likely to be 100% inoperative.
When measuring voltage on any circuit board, the board is going to be energized. It's best not to make contact with the live circuit. Most importantly, you want to avoid contact with high voltage present on some boards. For sensitive circuits, making physical contact with the circuit can result in changes in the circuit's operation. At the very least, the conductivity of your skin can skew readings in high-impedance circuits but that same conductivity can cause some circuits to malfunction, possibly to the point of causing component failure.
In the image below, the silicone rubber pad is placed so that a right-handed person could rest their left hand while probing the circuit and writing the values down with their right hand. This is the quickest way to collect readings if you don't have anyone to write the values down for you. The silicone rubber works very well. It's non-conductive and prevents your hand from moving, unexpectedly, causing the probe to short between closely spaced pins (which can lead to catastrophic failure of the amplifier, even if using current limiting or a low-rated fuse).
When checking voltage on a live circuit, having a probe slip or trying to get to difficult-to-reach points can cause headaches that you don't need. For a few tips that may be helpful, try THIS section of the Know Your Meter page.
Data Collection:
Now, back to the point of this section, collecting data. You'll find various .ods files in the tutorial. Some are templates while others include collected amplifier data. The .ods files are OpenOffice spreadsheet files with voltages for various components in an amplifier. Since there is no space for a keyboard (I don't like the pull-out keyboard trays) on my bench, I fill in the blank spreadsheet by hand (double-checking all voltages) and then either scan the paper document on a flatbed scanner or enter the values into the spreadsheet file on my computer. Whether scanned or in .ods form, there is a record of the voltages that you can use as a reference later. The image below shows the raw version. template - do not modify.ods is the blank version of the spreadsheet for OpenOffice (a free office suite) - Calc if you want to use it.
After you find it, copy it to the folder for the amp you're repairing (where you stored the photos of the amp that you took, for future reference) and edit the copy.
Click the link above if you're using Safari (preferred browser for opening files and folders).
If you're using Chromium Portable, copy the link address (right-click link and select copy link address) and drop into the address field of Windows Explorer. Using the Windows key + E will open the Windows Explorer file manager.
If you are capable of navigating your computer's file manager, and can go to the folder more easily, the file is in the following location:
repair_tutorial\ods template files\templates to be edited
Navigating directly to files locations is much quicker if you have the Everything Search Engine installed. Drop a folder (i.e. templates to be edited from above) or file name into the address field and it immediately comes up.
You'll find data like you see above helpful when you have intermittent problems. Taking the voltages when the amp is working properly AND when it's malfunctioning can help you to see what changes and can help lead you to the problem.
Need Help?
If there was anything in the previous section that was not clearly explained (either in the text or on the linked pages) or if you have questions about something covered above, email me at:
babin_perry@yahoo.com
Examples of Various Electronic Devices
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The board in the image above has 'through-hole' components. For those, pin 1 often has a square solder pad (zoom-in to see it). The same goes for pin 1 of many/most through-hole transistors. The IC above has a line on one end of the body. That end of the IC has the first and last pins (numbers 1 and 8 for this 8-pin DIP IC). The IC above provides both the line and a notch. Either/both are going to be found on the IC, depending on what the manufacturer chose to use.
For both types of ICs, the notch in the silkscreen outline (when used) will indicate the pin-1 end of the IC.
The board below mainly uses 'surface mount' or 'SMD' components. Some (none below) SMD ICs also use a line to indicate the pin-1 end of the IC, as you saw above. If you look at the ICs below, there are several that have dimples. These all tell you that that's the end with pin number 1 of the device. If you find an IC of this general configuration that has no such mark (only text), looking at it with the text right-side-up, the bottom left pin is pin 1.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
This doesn't necessarily apply to an IC with terminals around the entire perimeter or for ICs with terminals distributed in a matrix under the body. For those, look up the datasheet for the pin numbering scheme.
Identifying Pin 1:
Various manufacturers (both IC and Amplifier manufacturers) use their own ways to identify pin 1. Virtually all will have pin 1 on the left edge, bottom when the text is right-reading. Here are a few examples.
This first one has the notch in the silkscreen, the cut-out notch in the molding and a dimple/indentation on pin 1 of the IC.
In the silkscreen below, you see a triangle and a beveled corner used as pin 1 indictors. The IC uses a dimple.
This one is of an optocoupler and they are somewhat different, for some reason. The IC itself uses a sloped front edge on the edge that has pin 1. Its silkscreen uses the notch. The second image with four 4-pin ICs (also optocouplers) have a square notch cut alond the entire front edge. The board layout uses a square pad for pin 1.
These two ICs use a line to indicate the pin 1 end of the IC. The silkscreen uses a notch as well as pin numbers being printed on the board.
The SIP IC here has a notch in the top of the IC that marks the pin 1 end of the IC. The PC pad is square for pin 1.
In the next image, you can see that the silkscreen has an additional line that frames pin 1.
Repair Difficulty
This section was moved to its own page. It's not critical information. It's more of an idea of the general types of repairs you might expect to see and to help you decide if they're worth your time.

Prevent Headaches/Damage
The following is a list that should help you from making a few of the most common mistakes. These are important and can help save you significant time and money.

Learn the Trade or Find Another Line of Work
Foreword:
The text in this small section applies to those who are charging for the work they do and are charging the owners of the equipment for the perfectly good parts that they're replacing. If you are just absorbing the cost of the perfectly good parts you replace or are working on your own equipment. You're cheating no one (other than yourself if you won't take the time to ask for help or read the available material).
Again... Parts Changer << VERY Bad!
If you're proud of getting an amp working by randomly replacing perfectly good parts until you accidentally stumble upon the faulty part, you have the wrong mindset. People who work like that are incompetent "technicians" and if you charge the owner for replacing perfectly good parts, you likely fall into the category of being crooked.
How would you categorize a mechanic, HVAC tech, plumber... that did the same thing to you? And, I know, there will be some reading this that do all of their own mechanic work (including complete rebuilds on race engines) and can repair anything else that they own. This won't likely apply to you. If you're intelligent enough to do all of that, learning what's in this tutorial will be no problem and you would have no reason to blindly replace perfectly good parts.
Somewhat Random but Relevant Notes
Much of this is covered in detail in other parts of the tutorial. This is an introduction to the process. The following is a basic sequence of tests that you'll perform when you repair an amplifier.
Work Methodically:
When you begin to do anything, act as if someone (company owner, supervisor, head technician) is looking over your shoulder and will want a logical reason for what you're doing. Would there be that logical reason for what you're doing or are you acting blindly, out of ignorance? << Before you start chewing nails and spitting out barbed wire... Ignorance is simply the lack of knowledge about some subject. Everyone is ignorant about something. Ignorance has nothing to do with intellect/intelligence. If you don't want to appear ignorant about electronics when you work with a competent tech, do the hard work to learn the trade. It's as simple as that.
There have been a number of people who have asked for help with strange problems that didn't need to be problems. When performing any type of repair, you should do so in a logical, methodical way. Too many people are trying to test various points in ways that I've never even thought of doing and are sending me oddball meter readings.
As a simple example, when you measure voltage, you have to place your black meter probe on some point. That will be your reference point. Before choosing that reference point, you should fully understand what you're measuring and what the proper reference for that measurement is. The proper reference point isn't always the ground terminal on the amp but it's MUCH more likely to be the reference than the B+ terminal. I don't know where people get the idea that the B+ terminal is where they should place the black meter probe... but that's what some people do.
How, Precisely, is the Amplifier Malfunctioning?
When performing repairs, you test the amp to see how it's malfunctioning, find and replace the defective components and re-test to see if all problems have been solved. A competent technician will understand the various components and will know what those components need to function properly (various voltages, etc, ground on the correct terminal[s]) and will confirm that all are present and correct. Where they are not correct, he will determine why and work logically, from there to find the fault (out_of_tolerance resistors, defective voltage regulators, open traces...).
Don't be 'That' Guy:
Again, far too many people refuse to take the time to learn the way that the basic power supply driver ICs (TLx94, SG352x...) function (not even on a most basic level... Oh wait!... It's all on a basic level) and if an amp won't power up, they blindly replace a perfectly good driver IC with another perfectly good driver IC and... it's a huge waste of time. Take the time to learn the components. If you don't, you will never be a competent technician.
Before blindly replacing parts, please email me. It costs a lot less to send an email than it does to replace perfectly good parts.
babin_perry@yahoo.com
These ICs can sometimes present confusing behavior but, for the most part, there are a small number of terminals that have to have supply voltage or be grounded or have various terminals below about 3.5v but there's not much more than that to understanding them... and people still replace perfectly good ICs. If you feel that the few notes here are a bit weak regarding driver ICs, you're absolutely right. There is far more on the Power Supply Troubleshooting page (approximately 15 pages on the TL494 driver IC, alone). Remember, this is still only the first technical page of the tutorial.
The replacement may not actually be perfectly good if it wasn't purchased from a reputable distributor like DigiKey, Mouser... Sources like eBay/Amazon are not good choices for buying semiconductors. There are some reputable sellers but there are also MANY sellers who are selling counterfeit or second-rate components. I know... you already have accounts set up at eBay/Amazon and it's too much trouble to sign up for a free account at distributors where competent techs buy their parts. It's likely many of you will not heed this warning until you've spent days/weeks fighting a repair, only to find that the bargains that you found on eBay/Amazon are junk. eBay and Amazon are perfectly fine if you need a new fishing hat, semiconductors...NO!
Basic Test Equipment:
Also, expect to have unreliable/misleading readings from cheap multimeters. In a later chapter 'Know Your Meter', you will see examples of this. Many cheap meters have lots of features but have circuits that produce readings on what the meter 'thinks' it's seeing. A more expensive, complex meter will have more sophisticated circuits and firmware and can produce reliable readings. Now, I don't expect a hobbyist to go out and spend $400 on a new multimeter but if you're using a cheap meter that appears to have all of the features and capabilities of a more expensive meter, don't expect the same reliable readings of the more expensive meter. You should also know that there are relatively inexpensive meters (like the Fluke models 10, 11 and 12 will be seen on the equipment page) that are often better suited for troubleshooting than an expensive meter.
I'm no elitist. For general repair work. My meter of choice is a Fluke 10, 11 or 12. I understand that not everyone has access to the perfect equipment. This is one reason that so many alternative methods/suggestions are given through the tutorial. If all you have available is a meter that is less than ideal, at the very least, test it extensively to find it's faults and use it within those limitations.
Making Assumptions << Avoid:
Many times, the owner will assume that a red LED means that the amp is in protect mode. Some amps (many Kenwood amps and others) use a red LED for the power LED. For many of those Kenwood amps, there is no protection LED. If the amp is in protect, the red LED won't turn on. For those who never really paid attention, a red power LED can be confusing, especially if the system has a problem, like one speaker not playing.
If the owner calls before dropping the amp off to you, you may be able to ask a few questions and resolve the issues he's having without having to stop work to check out his amp. If you can get him to email you, that can be even more productive in many cases. Email is good because you can give him a list of points to check and he'll have all of them in writing. If you give him a list on the phone, you can be sure that he'll forget at least some of what he needs to check. If you're busy, tell him that you charge $20 (or whatever you choose) to check out an amp but will help via email for free.
While not absolutely necessary, it's often good to number each question you ask and then leave a blank line (to set off each question) between that numbered question and the next numbered question. Then, if they don't answer one of the questions (the fourth question), all you have to type is #4?.
LED Output Colors:
Above, the red LED in a Kenwood was mentioned. These LEDs typically (always?) have a red lens. A red lens means that the LED will be only red and can't be a multi-color LED (the type often used for both power-on and protection). LEDs with a clear lens could be any color, even multi-color. It's common for a 2-color LED to be used as 3 color LEDs by lighting the two main colors at the same time to make the third color (red and green lit together make orange, approximately).
More Professional Options:
When marking receipts, invoices, repair tickets..., there are a few terms that may make it look a bit more professional than writing P.o.S. on it. A price quote for a repair is 'approved' or 'declined' by the owner. If the amp isn't worth repairing, the term 'uneconmical to repair' (UTR, shorthand) is commonly used.
Don't Destroy Perfectly Good Test Speakers:
Some amplifiers will drive rail voltage to the speaker terminals when they fail. This can very quickly destroy the test speakers (covered on the Equipment page, item #9). If you don't have the DC blocking capacitor shown under item #9 before connecting speakers to the amp apply power to the amp (including remote voltage) and measure the DC voltage directly across the two speaker terminals for the channel being checked (red probe on the positive speaker terminal and the black probe on the negative speaker terminal). If you read more than a fraction of a volt, the amp is in need of repair. Typically, you'll have less than 50mv (0.050 volts) DC across the speaker terminals. Do this with no input signal to the amp (no RCAs plugged in or volume at minimum).
The DC is what's important because it may not be obvious when you connect a speaker has DC voltage driven into it. You should hear a loud click or pop but you may miss it. This is especially true if you connect the speaker and then power up the amp. Working in this sequence may not produce a pop through the speaker if the amp has a soft-start feature. ...One more instance where it would be necessary to have your scope on DC coupling if you were looking for DC with your scope.
If you have an excessive AC voltage across it, that's going to be obvious because AC voltage would cause a loud tone to be produced. The exception, where AC may not be audible, may be ultrasonic oscillation but that's rare... Actually both of these are rare for class B or class AB amplifiers. DC is the normal output when the amplifier has a fault that causes it to drive voltage to the speaker terminals.
If you want to check for ultrasonic oscillation, you can do so with your scope.
While it's not very common, it is possible to have oscillation on the speaker terminals of a class D (switching) amplifier if it has a shorted inductor in the LC output filter and has blown through all of the filter caps between that inductor and the speaker terminals. If you've removed the cover, the blown caps should be either vented (tops blown open) or the caps being shredded.
An LC filter is nothing more than a low-pass filter. Class D amplifiers have a high-frequency 'carrier' waveform that's modulated then filtered out, leaving only audio. It's very like the low pass crossover that you'd install on a midrange or woofer to filter out higher frequencies.
It's important that you not use the primary ground (the main supply ground) as the reference (point of contact for the black meter probe) because various faults can make the primary ground an unreliable reference point. Measuring the voltage directly across the two speaker terminals for each channel is the most reliable way to test for DC voltage.
Click HERE to open this graphic in a new tab. Right-click to zoom. Left-click to drag.
Alternatively (when looking for excessive DC voltage on each channel), you can touch your scope probe to the 'live' (bridging) speaker terminals but there can be a few different issues with using the scope. If you have it in AC coupling mode, you may miss the DC, if present. If you don't realize that there will be signal on negative (bridging) speaker terminals and only check the positive terminals, you could miss the DC on the terminals. If the amp is internally bridged (like the Massive 3000) and you only check the positive terminal, you could miss the DC. Touching every speaker terminal with your scope probe will prevent most of these mistakes.
The paragraph above was to help prevent damaging speakers but can also be helpful in troubleshooting. When an amp has a fault (such as shorted output transistors) that will drive DC voltage to the speaker, it generally immediately drives the amp into protection mode. That means that the DC going to the speakers will only be a pulse that lasts as long as it takes for the protection circuit to respond and shut the amp down. This is such a short period of time that it's difficult to see with a multimeter or a scope.
Just to clarify...
It was stated that you may not be able to see a fast pulse with a scope. Unless you have a storage scope, you may not see the pulse. A scope can easily display fast pulses but that applies to a continuous train of pulses as you would have in a switching power supply or in a class D output stage (examples of both will be given later in the tutorial). For an analog scope, there is a short delay between the input and the displayed waveform. This can prevent very quick, non repetitive, pulses from being displayed. You could use your scope in X-Y mode and that should eliminate the delay in displaying the pulse... Or, you could try one of the following.
Options?
The two most obvious options are to use a fairly rugged speaker with NO capacitor in series with it. The second is to use a less rugged speaker with a 100V+ capacitor in series with it. A 10uF mylar/film cap will work. If you're using your normal test speakers (6x9?), you likely already have a 100uF bipolar in series with them. That's OK as well.
You can't reliably use a capacitor alone. If you have DC, the capacitor will charge on the first application of DC and the subsequent pulses may not be audible. Connecting a 10k ohm drain resistor across the capacitor will help prevent the cap from remaining charged. The resistor and parallel capacitor make up what was referred to as a bass-blocker.
A 'drain' resistor isn't a special type of resistor. 'Drain' is its function. It drains the charge in the capacitor. The resistor can be just about any resistor. A standard 10k 1/4w resistor would be a good choice.
The speaker-based options above will allow you to hear a tick or pop as the amp tries to power up. If you connect the speaker to one channel at a time and power the amp up several times when checking each channel, you may hear a pop that alerts you to which channel is causing the problem. This isn't something that you would commonly do but it can sometimes help in troubleshooting.
The Ever-Versatile Incandescent Lamp Option?
Another option would be to connect a 120v incandescent lamp (incandescent, not LED, not CFL/fluorescent) across the amplifier's speaker terminals (no speaker connected unless protected as described, above), but, depending on the length and amplitude of the pulse the lamp may not light enough to be useful. The lamp can, however, be useful where an amp has a problem that causes DC to intermittently be driven to the speaker terminals, especially where the DC is causing too much of a pop through your capacitor-protected speaker.
To find what you can expect from the lamp, tap its terminals across the secondary ground and one rail, very quickly, then hold it to see what to expect if DC is applied to the lamp. Bear in mind that, when testing the brightness across the rectifiers, the lamp will draw some current from the amp so watch the temperature of the PS FETs if they're not tightly clamped to the heatsink. This test will take only a few seconds so heating isn't likely to be an issue.
The 'LED' above was a 120v LED lamp which may have various circuits and may or may not be of any use there. What would work is a pair of reverse-parallel connected LEDs with a series resistor. These would be fast to light up and could likely be made from bits and pieces that you already have. A similar piece is shown on the TT6 page, item #19. You wouldn't use the series-connected capacitor. The resistor would need to be chosen based on the rail voltage. The value would have to limit the current, for full rail voltage, to what's safe for the LEDs you would use.
Using the lamp, connected directly across the speaker terminals of the channel producing intermittent DC, you would push on various part of the board, on various components, heat, cool... do everything you could to try to cause the amp to produce the intermittent DC.
12v Power Supply Protection Circuits:
You need to know that many (most) 12v power supplies (the ones used to convert AC mains voltage to 12v DC) have built-in protection circuits. When an overload is detected on the power supply, the power supply will shut down the output and the voltage will drop to a couple of volts or less (to 0v if the protection is provided by a circuit breaker). If it's an automatic protection circuit, the voltage will go back to 12v when the overload is cleared. I prefer the simple current limiting resistor but if you won't use one and rely on the current limiting or over-current protection of the power supply, get to understand how it works so it doesn't confuse you when the amp draws significant current. Amplifiers without a softstart circuit will have a significant inrush as the rail caps are charged. This is normal operation for many amps.
Starving an Amp for Current:
This happens a lot so it bears mentioning. Some people are so afraid of damaging parts that they limit the current too much on their power supplies, starving the amplifier for current. In MANY cases, this causes the low-voltage protection to prevent the amp from powering up. The problem becomes a low-voltage problem because when a 12v power supply limits the available current, the output voltage drops (the same as with a series current limiting resistor, but not always as predictable as using the resistor). Even if the amp doesn't have a dedicated low-voltage protection circuit, the driver ICs have a minimum voltage requirement. If an amp won't power up, allow more current while very carefully watching the current draw and the temperature of the heatsink-mounted components (if they're not tightly clamped to the heatsink). If it attempts to power up, but won't and any components are getting hot, that can quickly lead you to the fault and is much better than wasting hours due to excessive current limiting.
As an alternative to current limiting, use a 10-15 amp ATC/ATO fuse and clamp all semiconductors down tightly to the heatsink as was suggested above. For more on current-starving an amplifier, click HERE.
Sounds for Use When Troubleshooting
A 'signal source' was previously mentioned. In many instances, the best signal source is a standard head unit playing music. Although the radio is annoying due to commercials, it's good because there is virtually never any silence. If you use a sine wave generator or test tone files, beware of these... If you use a frequency that's filtered by the amp's crossover, you may be led to believe that the amp has no output. If you use a sine wave that's the same frequency as the mains frequency in your area, sensitive circuits could pick up that noise and make you think it's your test signal. This is made more likely if you have fluorescent lamps/lightning nearby.
The test tones were available when you downloaded the tutorial. They can be used. There are also various test tone tracks available in the temp folder of the bcae1.com site. The 80hz800hz8khztestsignal01 test tone is a good track that won't typically be blocked by a crossover. It's available HERE.
For class D sub amps, I'd recommend using a test tone less than or equal to 100Hz. If you're using a function generator (Equipment page, item #12) to produce the signal, you will set it to produce a sine wave, not a triangle or square wave. If you're using your phone, portable mp3 player, tablet or laptop as the signal source, you should know that some amplifiers will not work properly if the signal source is not grounded to the same ground as the amp. This has caused significant time to be wasted for too many people. Again, on the Equipment page, item #11 shows a simple way to get a shield ground even if you don't want to use a proper head unit for a signal source.
Another alternative is various types of noise (pink, white, brown). White and pink noise cover the entire audio spectrum. These are generally used to test frequency response but can be used for a signal if you don't feel like listening to music. White noise is flat across the spectrum. Pink starts off on the low end of the spectrum at the maximum output level, then rolls off at 3dB per octave. Brown noise is similar to white but rolls off at 6dB per octave. These are in the Test Tones you downloaded when you downloaded the tutorial. If you didn't get them or if you want to get the latest version of the tutorial, email me.
babin_perry@yahoo.com
A music track will be suggested below.
Audacity:
This is a program that can generate the various test files that you may want or need for troubleshooting and/or testing. It's relatively easy to learn and use. The download link is under item #22 on the TT10 page.
Don't get discouraged if you're lost at this point. This page is nothing more than an introduction. I will begin filling in the blanks and going into much more detail. Continue reading the pages in order and the overall operation of an amplifier will become much more clear.
Familiarize Yourself with Various Amplifiers:
If you want the following page to work as smoothly as [insert something that's really smooth here], switch to the Safari browser before going to the next linked page. It makes everything work so much better. You can use other browsers and eventually get the destinations to work but with Safari, click and it's done.
In the directory, there is a link named Images and Notes for Other Amplifiers. Below that are links to pages with information on individual amplifiers. In the miscellaneousstuff folder there are files/folders for more than 100 different amplifiers (thousands of photos). Some pages have thumbnails and links to larger, higher quality images. For others, the high resolution images are in the folders. For many amps, you will find notes for common problems.
For reference and to make it easy to find, this page is 2 chapters above the Website Section directory. The link (has a blue underline) to the '- Directory - Website Section' is provided on the home page of the tutorial. This section of the directory is easily identifiable as you scroll down in the main directory because chapter icons end at the website section. The page you want has a white icon with a few amp manufacturer names. The page includes a significant amount of information about using Windows (for those who only know how to use Android or iOS). For those who know Windows well, you can click the 'MiscellaneousStuff Quick-Links' link at the top of the page to jump beyond the Windows instructions.
Many buyers have completely missed the information and images in the miscellaneousstuff folder mentioned above. If you don't read through those folders, you will miss a VERY large part of the information that you paid for.
The amplifiers range from the very old (mid 1980s) to some relatively new models. If you read through all of the pages and look at all of the images, you will become more familiar with amplifier layout and common problems.
Click on any files in the Windows file manager folder. swf, gif, png and jpg files are graphics files. txt files are text files (will likely open in Windows Notepad) htm and html are website type files (which will open in your default browser unless you select a different browser).
Default Browser:
You can set Safari as your default browser and cause no change in the use of your preferred online browser. Very few people store web pages on their computer. All commonly visited web pages are linked in the preferred browser which is opened directly. If you don't want to set Safari as your default, you can right-click and open the website type files in Safari by choosing Safari from the drop-down dialog box when you right-click on the website type file.
Right-click >> Open With >> Safari
Save Yourself Some Time for Older Amplifiers:
Before working on any amplifier, you REALLY need to browse the folder(s) for the manufacturer of the amp that you're repairing. You may not find the exact amp you're working on but similar amps may have similar problems and the notes may help you from making mistakes.
When you open a sub-folder in the miscellaneousstuff folder there may be many files and you'll have to search for the txt or htm files. If you sort the files by date modified (most recently modified at the top), the txt and/or htm files are likely to be at or near the top because they're the files that repeatedly get modified/edited.
If you don't have a good graphics viewer, use Irfanview. When it's being installed, it will ask you about file associations. Select only JPG, PNG, TIF and GIF. De-select all others until you decide that you like the viewer.
Another good viewer is the FastStone image browser. It's also free. Both of these viewers allow you to step from one image to the next with the mouse scroll wheel. If you are going to view more than a tiny fraction of the images, this will be a very important feature.
The images in the individual amplifier folders are typically very large. It is unlikely that your monitor will be able to display them at full resolution AND have them fit to the screen. There are two options. You can allow the browser to resize them (and allow the entire image to fit on the screen). Or, you can allow the image to appear it's actual size and use the scroll bars to see all parts of the image. The first option will result in relatively poor resolution. The second option will give much better resolution.
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