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Basic Troubleshooting
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Troubleshooting computers is like solving the problems you solve in everyday life. Once you understand the basic structure, you can easily determine where the problem lies. Of course, this page is designed to guide you through the steps that are generally taken when a computer fails to operate properly. If you have only one computer and it fails to function properly, this will do you no good (it can't be read on a computer that is inoperative).
If your computer fails to power up (you can hear no fans running and no lights are lit when you press the power button), check the following:
If the lights light up when you press the power button but you get no display, check the following:
If the computer and the monitor have power but you still cannot get it to operate, you may want to have it checked by a computer tech. If you are somewhat adventurous and want to try a few more things, read on. Many times, a computer will not power up simply because one of the connectors on one of the components inside the computer isn't properly seated. If the computer was moved (or dropped) just prior to it becoming inoperative, there may simply be a loose connection). To check this, unplug the AC mains power plug from the computer's power supply (this is very important). Pull the left side cover off of the computer. On all connectors, gently press them to be sure that they're properly seated. There will likely be be several power supply and IDE connectors that are not to be connected so don't be alarmed if you see connectors that are unplugged. After you've checked all of the connectors, replace the side cover, plug the power cord into the computer's power supply and try to power up the computer. If it still won't power up, you may need to call a technician. However, if you own (or can borrow) a multimeter and you want to check a few more things, go to the next section. If, when you press the power button, the computer's fans start to turn, then shut off, you could have power supply problems or there may be something loading down the power supply (causing it to go into protective shutdown). When you press the power switch, the green wire in an ATX power supply is connected to ground (by the motherboard, not drectly grounded by the switch). At that point, the power supply is switched on and all of the various voltages are generated. When the various voltages are within a specified tolerance, a signal is generated on another of the power supply pins (the power OK pin) and the processor is then switched on. All of this takes well under a second and most people never realize that it's happening. ATX power supplies can be tested by disconnecting them from the motherboard and connecting the green wire to any of the black wires. This will turn the supply on. At that point, you can test the individual voltages. If all of them are close to the rated voltage, the supply is likely OK. If the power supply tried to start but wouldn't start (or wouldn't run for more than a second) when it was plugged into the motherboard, you should suspect that something is pulling too much current. Plug the power supply back into the motherboard and disconnect all of the drives' power connectors as well as any accessories such as fans. Again, try to power up the computer. If the PS starts normally, begin reconnecting the power supply to the accessories and drives (one piece at a time and trying to start the machine after each piece is plugged in). If you find that one piece is preventing the machine from starting, you've likely found your problem. You may be unaware of the fact that the actual output voltages are rarely precisely at the rated voltage. The following voltages are from a relatively inexpensive supply. The variation from the rated output that you see here is relatively common and this supply will work fine in most computers. Of course, when the power supply is loaded by the computer, the voltage WILL change somewhat. This is an UN-loaded power supply. As a side note, sometimes the output voltage of some of the outputs will actually increase when the supply is loaded. This often happens when the regulated output (generally the +5 volt output) is loaded down. The reason it happens is that the pulse width of the power supply is increased to maintain the regulated 5 volt output. When the pulse width is increased, all of the other outputs will increase (the 5v output should remain constant). Recently, some power supplies have begun employing two independent sets of regulators. This will help keep more of the output voltages within a tighter tolerance.
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![]() If the machine will not start with no accessories plugged in but the power supply powers up fine with the green wire shorted to the black wire (don't try shorting green to black while it's connected to the motherboard), the processor may be dead. This is a somewhat difficult situation. When troubleshooting computers, it's common to simply replace the questionable component with a known good component. Since you won't know whether the motherboard or the CPU is defective, you may want to plug the questionable CPU into a known good test board. If the test board has insufficient protection and the CPU is shorted, the PWM regulator in the test board could be damaged (leaving the board irreparably damaged). If you plug a good CPU into a questionable board that has a defective PWM regulator, then you will kill the test CPU. Many times, if you have a blown CPU, it's best to replace both the CPU and the motherboard. If you decide to swap the CPU to check it, make absolutely sure that you have the correct heatsink properly installed BEFORE applying power to the unit. Some CPUs have no thermal rollback/shutdown protection and if the heatsink isn't properly installed, the CPU will fail within seconds.
When you assemble a new machine, sometimes it won't boot up the first time you turn it on. The problem could be a defective component, a connector that's not properly seated or a BIOS/motherboard setting that isn't right. These are just a few of the possibilities.
Sometimes, a computer will simply fail to boot. If you haven't done anything that could be causing problems (installing/updating software/drivers), some of the system files may have become corrupted or some piece of hardware may have failed. If the computer starts to boot (it shows signs of life), it means that the power supply is probably OK. If it repeatedly fails to boot into Windows, you need to try booting to 'safe mode' (covered earlier in the tutorial). If it boots into safe mode, it indicates that the computer's hardware is likely OK and the problem is probably software/driver related. Unless you want to go through extensive troubleshooting, the best thing to do is to go back to the last restore point. Restore Points were covered earlier in the tutorial.
If you installed a new piece of hardware to upgrade an older (but still functional) piece of hardware, the first thing to do is to remove the new piece and reinstall the old component. If the system again begins to boot and works as it did before, the new piece of hardware could be defective or causing some conflict in the system. Its drivers could be corrupt (if you downloaded them) or they may have some sort of incompatibility with your other hardware/software. If you're not going to try to reinstall the new piece of hardware, you should uninstall the drivers for the component that you tried to install. If the machine will still not boot after reinstalling the old component, you may have pulled a connector out of its socket. Try pushing on all of the connectors on all components (don't forget the memory modules) to be sure that they're all properly seated. If that doesn't work, try booting into safe mode. If it boots there, your hardware is very likely OK and you simply have something loading during boot-up that's causing the system to crash. At this point, you can do a couple of things, you can go back to the last restore point (it should have been created when you installed the drivers for the component that caused the problem). You can boot in safe mode and uninstall the drivers that you recently installed and/or you can go through the startup list (run >> msconfig >> startup) and start removing components until the system boots. If you're removing items from the startup list, begin with the ones that seem to be related to the hardware that you recently installed.
If the computer attempts to boot but crashes repeatedly, boot to safe mode and go to START >> CONTROL PANEL >> ADD AND REMOVE PROGRAMS and uninstall the software. We covered the procedure to uninstall software earlier in the tutorial. If the computer still refuses to boot, you may have to go back to the last restore point.
One of the most important tools for troubleshooting strange software problems is Google. There is no way that any one web site can cover every problem. If you have a problem, take note of the EXACT wording of the problem (take and save a screen-cap if you have a poor memory) and search Google. If you enclose the error statement in parentheses, it may make the search more successful. You may have to follow several links because many of the solutions offered on the forums or in the newsgroups will not be the solution for your problem. If you're having trouble with a specific piece of software, try the software's home page. Look in the 'support' and 'FAQ' sections of the site.
Sometimes, a computer will not boot due to a corrupt file in the OS or a defective hard drive. The problem you face is determining which is the culprit. To make it easier, you can use one of the 'live CD' versions of Linux. The live CD version will run entirely from the CD. The hard drive will not be used unless you choose to do so. This means that you can boot a computer without a working hard drive. After downloading any one of the many free live CD versions of Linux, you burn it to a CD. When the live CD is in the CD ROM drive and you boot, the computer will boot to the Linux OS (assuming that you have the boot order set with the CD having higher priority than the hard drive). When it boots, the Linux OS will load drivers for the LAN, sound cards, video cards and anything else that's needed. Although, it can not possibly have drivers for everything, most of the live CDs do a very good job of finding suitable drivers. While using the Linux OS, you can check the drive. It will allow you to go through the various directories just as you would in Windows. Keep in mind that the terminology is somewhat different than in Windows and it may take a bit of time to get used to the OS but in time, you can easily master it. While in the Linux environment, you can use any of the various devices (LAN, sound card, video card, CD/DVD drives...) to determine whether they're operational or not. I've used the following live CDs: Notes: Below is a screen-cap of the Knoppix desktop (the actual desktop looks much better, cleaner). As you can see, I've opened the 'My Documents' folder. The interface is similar to Windows.
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Perry Babin 2005 All Rights Reserved
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