How to Diagnose Bad Parts
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We all have them.... problem children...  and in our case... personal computers.  The following is a general overview of what to do with temperamental computers...

First check:

• Does the machine have a tripped circuit breaker?  Check the back of the box
• Did you just add a new board? Take it out and see if the problem corrects itself...
• Is the machine booting, but just not behaving? Check your conflicts
• Before you "remove the top and begin to swap" - do the laziest thing first... if the video doesn't appear to work, swap monitors before swapping video cards.....
• Identify if the problem is hardware or software - if the machine boots, and only hangs on one program - it is probably software and not hardware.   Possible causes: bug in software, incorrectly installed, card or driver not compatible with software
• Check the vendor's website - often times, they will list the known bugs & offer a fix for them.

Raising Up the Dead (Computer that is)

General Rule of Thumb 1 - Assume there is only one problem - Unless you know the machine has had a catastrophic power hit, there will generally only be one problem.

General Rule of Thumb 2 - if you are getting absolutely no response to the machine at all - swap the power supply before the motherboard - it is the usual culprit. If the fan is blowing and the unit hums or buzzes with power, then you can assume that the power supply is ok - move onto one of the two approaches below.  If the fan doesn't start right up - the problem is simple - you cooked your PC the last time you used it. 

It is possible that your power supply is smart enough to know not to start up if there is a short in the motherboard - however, you should get some sort of response from the fan, even if it is brief.  If you do not get a moving fan when you try to power up, suspect the power supply.

When a power supply starts up, there is usually a quick 'click' sound from the speaker.  Once you hear the click, the power supply is telling the motherboard that it is ready to go.  If you don't hear the click - you probably have a bad power supply.

Tip: With the computer shut off, unplug the power supply from the motherboard and then turn the computer back on.  If the fan operates when disconnected, but not when it is connected, it is a good sign that the motherboard is headed to the motherboard graveyard.

Approach One: Two machines - hopefully you have the luxury of two machines - one well and the other not so well. 

Swap out parts one at a time. After testing each part, put it back in its original computer - you don't want two dead computers do you?

When you find the part that doesn't work in either computer - assume you have hit the jackpot. Cross check it by taking the same part from the good computer and putting it in the bad computer (with the rest of its original parts in place) & try to boot up.  Remember that most of the parts you could possibly swap are configured in the CMOS & it will have to be adjusted for the machine to boot entirely.  You may want to do this in order to retrieve lost data from a machine - but otherwise, you might not want to actually change CMOS settings - it might be enough to know that the machine will boot once you have good parts in there.

Approach Two: One machine - 

Strip down the machine to the bare minimum. Add parts back in until it boots or behaves abnormally - viola, the bad part!

The Bare Minimum:

• Power Supply
• Motherboard
• Speaker
• Memory

Then add back in: 

• Video Card
• Hard Disk Drive

Turn it on - you should observe several things: The fan should start up.  If it doesn't - it is pretty straightforward as to what the problem is - the motherboard, or the power supply.  Start by swapping the power supply first.

Assuming it does start up (see above if it doesn't), you should hear a series of beeps - it is saying "Where is the video card?" So, the next step (after powering down of course) is to add the video card. If you get past this phase, start adding the other components in, one by one and noting the behavior of the machine. When you get to a point where it won't boot after installing a particular unit, suspect that unit.

Reference: PC Upgrade & Maintenance Guide 2003 Edition www.sybex.com

Last Update: 05/28/2005 09:17:05 PM.