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Short overview of how to troubleshoot bad hardware when a pc does not post

nobus
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So, if your PC is old or new and it does not boot or has no display then what do you do?

Precautions :
-During connecting or disconnecting devices, be sure to have the AC electrical power disconnected
-Temporarily ground yourself, or use a wrist strap to prevent electric static discharges from destroying certain components.

Here are my troubleshooting procedures:

-With a new motherboard: verify if all mounting standoffs' holes correspond with the holes in the motherboard!!
   Or test the motherboard outside the case, on a wooden  (non conductive) surface
-Clean the system from dust, then  test with the minimum setup:
 - Disconnect all peripherals devices (including the drives, CD, DVD, printers and keyboard) and network cables, except for the motherboard + CPU + 1 ram stick, video card, monitor and power supply
-Verify that the 4-, 6- or 8-pin CPU Aux power plug is connected
-Verify that the VIDEO card has a power connecter - if yes, connect the power to it!

Now, power-on  your PC.  On boot, do you have a display?
-if NO it is one of the connected devices: RAM, Power supply , video card or monitor.  So, if possible, swap ram, power supply, video card or monitor - leaving only motherboard and CPU
-test the ram in each slot, sometimes you have abad slot, causing ram problems
-if YES, then disconnect the AC electrical power, and start reconnecting each of the peripherals, devices and cables (one at a time) until the problem shows itself.  Before each of these reconnections, you need to follow the precautions above.
*** note : if the fans are running, this shows there is 12 V present from the power supply; this does not mean the power supply is ok, you still need 3.3 V and +5 V as well; and other signals.

Additional tests and things to try :
-boot without ram, it should beep; (also, without video card)
-try the bios default settings, (if possible) or clear the bios by removing AC and the bios battery
-renew the CPU heat paste, and verify that the heat sink is mounted flat on the CPU, allowing for a good thermal contact
-you can also check the motherboard for bad capacitors as shown here :   http://en.wikipedia.org/wiki/Capacitor_plague
- test parts on another  PC to know what is ok - and what not - if possible
***note :  if you are using 4 sticks - note that many boards do not run well with the ram bus loaded heavily like that, causing deterioration of signal levels and wave forms ! --> so test with 2 sticks max ..

The term POST refers to the Power On Self Test  procedure - here a link  with a short explanation  http://www.pchell.com/hardware/beepcodes.shtml
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nobus
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Comments (19)

Fred MarshallPrincipal
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Commented:
nobus:  Sorry, if I was unclear:
Today I have an issue that's not covered here that I could find:
 The power supply does not turn on.  (Replaced it with a new one).  No fans, no lights, nada.
 The caps look good.
 I removed all the memory, disconnected all the peripherals power and still the same thing.
The condition where the power supply doesn't turn on at all AND the issue isn't the power supply itself doesn't jump out at me.  Granted I don't see this happen very often but I was left with the question.  Since then, my research suggests that it's not an often-mentioned problem.

Since then, you told me separately that clearing the BIOS would be a good idea as would checking the CPU pins.  These turned out to not be the issue in this one case but here I figure you're more about how to tackle such things.

So now I understand:
I didn't clear the BIOS originally thinking it wouldn't matter and asked: Would it?  I understand now that the answer is Yes.
I didn't fiddle with the CPU mount thinking it wouldn't matter and asked: Would it?  I understand now that the answer is also Yes.
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Commented:
in general, when a problem arises, you advance by eleiminating possible problem items, till the problem cause is found
that's why you need to follow in this case the bios sequence, and check all partts
fred hakimRetired IT
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Commented:
The step that always gives me the most heartburn, is after you have eliminated all the connected items (memory, video, PSU) and are left with deciding between the motherboard and the CPU.  

Sometimes, I don't have an available good matching part (correct socket/gen).  But even if I do I'm reluctant to put a possible bad CPU into a good mobo, or even more, a good CPU into a possible bad Mobo for testing,  my fear is a failing part could damage the good part I use for testing.   Am I just being paranoid?  How do you make that decision?
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Commented:
chances are  : bad mobo = 95 % - - bad cpu = 5%
so the choice is easily made
Fred MarshallPrincipal
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Commented:
You might briefly mention asking the question "is it worth it? for some of this.  It depends on the intended audience.
I tend to always replace the power supply first.  It's easy, it's cheap and there are generally PSUs on the shelf.
 I'd say the same: PSU 95% Memory 5%.

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