PC not longer powers up after clean up

H

hmz

2[H]4U
Joined
Jul 26, 2005
Messages
3,343
So I took my cousin's PC to clean it up, replace a few 120mm fans and shit like that. Was working fine.

Cliffs.

1. Replaced 2 120mm fans.
2. Replaced the stock intel HSF. Had to take it out the MB to install the back plate.
3. Put everything together and push the power button - no sign of life, except the light on the PSU turns on and the mouse lids up.
4. Tried to short the 2 pins on the MB, but still no go.
5. Double checked the cables. Everything is tightly connected.

So what happened?
 
So the PSU and mouse lit up, but did they stay lit up or just momentarily?

Can you ensure that the motherboard isn't shorting on a metal edge or screw?
 
Dark Shade said:
So the PSU and mouse lit up, but did they stay lit up or just momentarily?

Can you ensure that the motherboard isn't shorting on a metal edge or screw?
Click to expand...

Mouse and the PSU stay lit up.

Just removed all screws on the MB, but no go.
 
get it out of the case and build it up on the bench in a minimal config, mobo, 1 stick of RAM, CPU and GPU if no onboard video

short the on button pins and report back
 
jojo69 said:
get it out of the case and build it up on the bench in a minimal config, mobo, 1 stick of RAM, CPU and GPU if no onboard video

short the on button pins and report back
Click to expand...

This. Especially check the new HSF mounting.
 
ok, next try the paperclip trick on the PSU

disconnect it from everything and short pin 15 to ground

paperclip_psu.jpg
 
Forget to plug in any additional power cables on the motherboard? New fans causing a short?
 
jojo69 said:
ok, next try the paperclip trick on the PSU

disconnect it from everything and short pin 15 to ground

paperclip_psu.jpg
Click to expand...

Just tried this method and no go. So I guess the PSU is dead? But how could I killed it?
 
Did you remember to turn it back on? I know, stupid question...

I've had a strange PSU problem like this before as well.

I put in a new MB, CPU, GPU, RAM, etc. and for some reason it refused to boot up. The PSU was a good one, was less than 6 months old, and had plenty of head room wattage-wise for the new system. For some reason, it refused to turn back on...

I replaced the PSU and everything worked fine!

Then I took that "failed" PSU a couple of years later and put it in an old case with a bunch of old hardware just to see if everything worked for a build for my youngest son and presto, it worked fine...

It's a good reminder that everything electronic actually runs on PFM, not some microsopic movement of electrons. ;)
 
there you go, could have been worse

don't blame yourself, sometimes shit is just ready to break...who knows

what exact PSU are we talking about here and how old is it?
 
Ok, just tried to short the MB again with only one stick of ram, vga. Upon turning the PSU on, the cpu fan makes a move for like 0.5sec and stops. Same thing happens when powering off the PSU.

The PSU is a thermaltake 450W and it's old.
 
but the PSU does the same thing when you paperclip it right?
 
Whenever I test PSUs I hook up at least one fan to see if it starts up.

Do like mentioned earlier; hook up the PSU to the wall, hook up at least one 12v case fan, and short pin 15 to ground and if the fan starts up, then you know the PSU is at least turning on, you just don't know if it's supplying all the different voltages.

If you do this and it turns on, I'd reseat the CPU and HSF and try again.

EDIT: I just had a thought -- you said you replaced the HSF and added a backplate... could the backplate be laying on top of something on the backside of the mobo and shorting it out? Basically, you introduced the fault somewhere along the lines, so I'd look very closely at everything you touched and look for stupid problems.
 
Hooked up a 120mm fan, paper clipped the PSU and the fan starts spinning for like 5sec and stops. So, the psu is dead?
 
yes

open it up and have a look at the capacitors

(standard disclaimer about always unplugging mains powered equipment before opening)

my bet
2011-10-09_200331_caps_bulged.jpg
 
jojo69 said:
yes

open it up and have a look at the capacitors

(standard disclaimer about always unplugging mains powered equipment before opening)
Click to expand...

+1, PSU is toast... It should run that fan all day long without stopping. You didn't have anything else hooked up right?
 
Ah yes, the dangers of replacing heatsinks....

I cooked an Abit motherboard back in the day swapping a dustbuster coolermaster heatsink with a zalman for my brother.... (Decent rig too for its time: AthlonXP 1900+, 512mb ddr1, and a 9800pro). The look on his face.... So sad.

Anytime you have to remove the motherboard and pop on a new backplate etc. It's risky business in my experience....

The only bigger mistake I can recall was using one of those thermal sticky pads on a A64 3200+ instead of using thermal paste.... NEVER AGAIN.
 
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