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Brainstorming Needed (PC Repair)

Posted: Tue Jun 19, 2012 4:07 pm
by Yrzuli
So last night Anaie started having issues with his computer. He got a BSOD which pointed toward his vid card (NVidia), but while researching it, there seemed to be absolutely no consensus as to whether it was a driver issue, or a hardware issue. He's had these cards (SLI's pair) for a couple of years now. One guy had stated that when he removed his card he found melted transistors, so I recommended that we take out the 'primary' card and use the 'secondary'.

Prior to this, he'd tried changing drivers while in Safe Mode (the only way he could boot) to no avail.

As if this wasn't enough, now it seems like his power appears to be failing? Thought it might be the button itself, but today when I booted it up, I got it passed start-up to the Windows logo (sat there for 10-15 seconds) when the power suddenly cut off. The only power cables we changed where removing the ones to his old card.

I'm wondering if the sudden power failure could be coming from a signal from the CPU? While we were de-dusting the interior (don't think the case has been opened since we switched the video cards), I'd forgotten that I'd gotten what I can only describe as the most fucking stupid heatsink/fan combo in the world. It attaches to the mobo via little twist knobs, and I completely had forgotten that it would remove the entire thing, not just the fan. We had to fight with it to get it re-seated, but I didn't have any silver paste to reapply. Could this be causing the sudden power loss?

So fellow PC builders, give me your thoughts.


Sticking this here as a note to myself (gotta check, think my dad has a multimeter; hopefully if he does, he knows where it's at):
[quote]Try to verify (as well as you can) that the PSU works. If you have a multimeter, you can do a rough checkout of a PSU using the "paper clip trick". You plug the bare PSU into the wall. Insert a paper clip into the green wire pin and one of the black wire pins beside it. That's how the case power switch works. It applies a ground to the green wire. Turn on the PSU and the fan should spin up. If it doesn't, the PSU is dead.

If you have a multimeter, you can check all the outputs. Yellow wires should be 12 volts, red 5 volts, orange 3.3 volts, blue wire -12 volts, purple wire is the 5 volt standby. They can be checked in operation from the back of the main power plug.

The gray wire is really important. It sends a control signal called something like "PowerOK" from the PSU to the motherboard. It should go from 0 volts to about 5 volts within a half second of pressing the case power switch. If you do not have this signal, your computer will not boot. The tolerances should be +/- 5%. If not, the PSU is bad.

Unfortunately (yes, there's a "gotcha" ), passing all the above does not mean that the PSU is good. It's not being tested under any kind of load. But if the fan doesn't turn on, the PSU is dead.[/quote]

Re: Brainstorming Needed (PC Repair)

Posted: Tue Jun 19, 2012 4:18 pm
by Grainger
Auto, rapid power off like that suggests something is tripping the thermal sensors or the PSU is toast. No silver paste is a REALLY BAD THING (tm). Unless you lapped the cpu and the heat sink/fan your thermal conductivity is crap without it - like stuff is going to melt crap !! (That's probably why the machine shut off in 15 secs - cpu thermal sensor tripping)

A bad power supply is a bastard as it can, and will, cause just about any error message making you think its something else entirely.

Air cooled SLI (or XFire) rigs tend to get insanely hot too, heat failure of anything is always a possibility.

After fixing the silver paste issue I'd replace the PSU next.

Re: Brainstorming Needed (PC Repair)

Posted: Tue Jun 19, 2012 4:25 pm
by Yrzuli
My PSU should still be good, so I'm thinking of stealing it from my "dead" PC and re-wiring his. I really, REALLY hate that heatsink I got for his comp (I don't recall having issues with it originally, but dear god it was pissing me off last night!!) so I need to see if I can find old order slips stating what his CPU is so I can get a replacement heatsink.

Good to know that might be the source of the sudden power failure. It's what I thought, but needed a sounding board. (And there is the remnants of the paste on both the CPU and heatsink, I did not wipe them clean.)

Re: Brainstorming Needed (PC Repair)

Posted: Tue Jun 19, 2012 5:49 pm
by Pincus
Power supply. Also notoriously hard to test. A multimeter is really the first test, you also have ripple and power dips...and that test equipment is not common or cheap.

Re: Brainstorming Needed (PC Repair)

Posted: Tue Jun 19, 2012 5:56 pm
by Krinathalasa
Sounds like power supply too. When mine went it took my video and sound card with it somehow. Fucker.

Re: Brainstorming Needed (PC Repair)

Posted: Tue Jun 19, 2012 6:12 pm
by Kharzak
when bob's machine had a failing power supply some years ago it wouldn't even turnover. i guess on the scale of power supplies failing it was on the worse end. made it easy to diagnose without any tools

Re: Brainstorming Needed (PC Repair)

Posted: Tue Jun 19, 2012 7:36 pm
by Abric
I have a new (i.e. not used) PSU and a video card for sale! I may also have some thermal paste (for free). If you need me to search for it, let me know. Just don't text... phone is off.