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Edeneye asked on

Can I assume motherboard has failed?

I have a computer that exemplified thermal failure. It would shut itself down after a period of using it, the time frame getting shorter and shorter. Then it failed to reboot at all. This is all the person told me.

When I got it, it would not even POST. Upon visual inspection, the CPU heatsink was packed solid with dust. Other components looked ok.

After cleaning everything, the computer would still not POST. PSU tested out ok, but I swapped it anyway and still got nothing.

Then I stripped it down piece by piece until I only had the motherboard powered. Never did I get a post message or BIOS beeps of any sort.

Would you assume (like I have) that the motherboard (at the very least) has failed?
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PCBONEZ

8/22/2022 - Mon
ASKER CERTIFIED SOLUTION
Peter Hart

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rindi

That would most likely be the case. The CPU should still work though.
PUNKY

Did you re-apply thermal paste for cpu and heatsink?
Peter Hart

...and without thermal paste it not work...?
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nobus

>>  It would shut itself down after a period of using it, the time frame getting shorter and shorter. Then it failed to reboot at all.  <<    that points to overheating
>>   the CPU heatsink was packed solid with dust   <<    so does this.
the P4 cpu's have a thermal stepdown feature, so the most likely failed component is the motherboard; as said, but if you replace it with a newer one, you'll have to buy a new cpu as well (also said)
i assume the 4-pin auxiliary power plug is connected?   yellow/black wires?
PCBONEZ

Asus P4P800-xx boards are known to use Chem-icon KZG series and OST brand capacitors, both of which are known to be high failure rate parts.
- Especially if installed anywhere near a heat source. (CPU or VRM areas.)
PCBONEZ

Apparently some of them have shown up with GSC brand or Elite brand caps as well.
These two are worse than the first two I mentioned.
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ASKER
Edeneye

Thanks. That's what I thought, I just wanted to hear the same from someone else.
ASKER
Edeneye

Thanks everyone.

The symptoms and the lack of BIOS beeps led me to believe it was the motherboard, I just needed a second opinion.

I haven't (and probably won't) test the CPU which could be fried too, although the stepdown feature may have saved that, I don't know.

Visually the capacitors look ok, but I have seen bulging/exploded caps in the past. They could be the culprit though.

Thanks again.
PCBONEZ

For future reference (other readers to).
-
I've had a number of motherboards with failed Chem-icon KZG capacitors that had zero visible signs of failure.
-
They LOOKED fine, but if removed from the circuit and checked for capacitance and ESR with appropriate meters they are WAY out of specifications. (Capacitance low down to 1/3 to 1/2 of spec and ESR as much as 200x max spec.)
-
KZG are medium brown with white lettering. (KZG is marked in white too.)

.
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