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pc power problem

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Need some help diagnosing a pc problem. First time happened a few weeks ago. Shut down pc before bed, next morning I notice pc is still running(screen is black/off). Can't do anything except turn off… Read More
athunder Avatar
7m, 1w agoPosted 7 months, 1 week ago
Need some help diagnosing a pc problem.
First time happened a few weeks ago. Shut down pc before bed, next morning I notice pc is still running(screen is black/off). Can't do anything except turn off power. Try to turn back on but nothing happens.

After opening up, cleaning, and generally checking all connections, power suddenly comes on and works again, and continues to work fine, until today.
Same problem, shut down last night, this morning screen is off but computer is still humming. Powered off then won't start up. Opened, cleaned, checked, no obvious issues, still can't power up.
Changed power cable, suddenly it boots up!
Shut it down and moved power cable to original power socket, won't power up. Maybe it's power socket..moved back to one that worked, won't boot up again.

Little power light on motherboard is always on when switched on.
I'm stumped at what's causing this, thought it must be psu but why sometimes it works and power light inside is on.
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athunder Avatar
7m, 1w agoPosted 7 months, 1 week ago
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#1
Found a spare HD power cable inside and switched that around and it booted up.
Old power cable now in 2nd HD, and oddly, that is powered up and accessible too.

Seems to be working again now but im still :|:| at the cause of this.
#2
Is it just the PSU that hums? or are hard drives spinning up? Is the PSU on the old side of things?
#3
Did you build your PC yourself?
If so check that the motherboard isn't grounding with the case anywhere, check that the graphic card and any pci slot cards are sat correctly, check that the heatsink and fan aren't loose.

Assuming you've checked all these try sitting the case on it's side or stood up if it's normal on it's side then turning it on. If it boot then something is causing a short.

If it's still no booting then take everything out of the case. Paper clip method the psu to see if it powers on with nothing connected.
If it won't power on then it's the psu and it needs replacing, if it doesn't work then bare bones the system.
Start with just the motherboard (inc cpu and heatsink) and 1 stick of ram.If it boots then add any more ram then test again.
Repeat with the hdd, gpu and then anything else you have attached until it fails to boot.
Once it fails to boot remove remove the fault part, test it again then replace the faulty part.
#4
Fandango_Grim
Is it just the PSU that hums? or are hard drives spinning up? Is the PSU on the old side of things?

Primary is an SSD, so can't really tell, PSU is pretty old now(6 years old, wasn't cheap one, 800w + very quiet).

Edited By: athunder on Sep 19, 2016 17:28: more info
#5
joedastudd
Did you build your PC yourself?
If so check that the motherboard isn't grounding with the case anywhere, check that the graphic card and any pci slot cards are sat correctly, check that the heatsink and fan aren't loose.

Assuming you've checked all these try sitting the case on it's side or stood up if it's normal on it's side then turning it on. If it boot then something is causing a short.

If it's still no booting then take everything out of the case. Paper clip method the psu to see if it powers on with nothing connected.
If it won't power on then it's the psu and it needs replacing, if it doesn't work then bare bones the system.
Start with just the motherboard (inc cpu and heatsink) and 1 stick of ram.If it boots then add any more ram then test again.
Repeat with the hdd, gpu and then anything else you have attached until it fails to boot.
Once it fails to boot remove remove the fault part, test it again then replace the faulty part.

Yes self built, everything's connected, I had to turn it on side to open it up so that's already been done.
As mentioned above it's now running again since i switched the power cable inside to the primary SSD, but oddly the cable that was in the SSD is now in the secondary HDD, and that is also working.

Guess when I boot it up in the morning i'll find out if it's fixed or not.
thanks for the suggestions
#6
Are you shutting down the PC or is it going into a sleep cycle ? Removing the PSU cable will cause a full power down and reset if it's in a sleep cycle.
#7
kester76
Are you shutting down the PC or is it going into a sleep cycle ? Removing the PSU cable will cause a full power down and reset if it's in a sleep cycle.

I shut it down, although I don't normally wait around to check, last night shut down ok, and this morning boot up fine again. Seems a very intermittent fault, maybe it was that power cable to the drive.
#8
athunder
Fandango_Grim
Is it just the PSU that hums? or are hard drives spinning up? Is the PSU on the old side of things?
Primary is an SSD, so can't really tell, PSU is pretty old now(6 years old, wasn't cheap one, 800w + very quiet).


I mean, to me it sounds like your PSU is just under performing with age - if you DC your Graphics card from your PSU/Mobo (is it a power hungry 5-6 series nvidea? [you said your PSU was 6 years old]) and the whole thing springs to life you just need more Watts bro.

PSUs lose power over time, and generally speaking they have improved dramatically over the past few years, so you may not need to replace 800W for 800W.
#9
athunder
kester76
Are you shutting down the PC or is it going into a sleep cycle ? Removing the PSU cable will cause a full power down and reset if it's in a sleep cycle.
I shut it down, although I don't normally wait around to check, last night shut down ok, and this morning boot up fine again. Seems a very intermittent fault, maybe it was that power cable to the drive.

I think your confusing things here with a dead PC and a PC that doesn't boot. A dead PSU/faulty wont get past POST and may spin fans and power CDROMs etc but no POST. It sounds like your PC is posting but it isn't booting the HDD ?
I think your PSU is fine as any major issues with the 5v/12v rails and the PSU would be dead/standby and no way is that drive drawing too much power to boot. I would say that your HDD spin up time might be the issue or the drive could just be dying.

Make sure that you have set your bios only to boot your OS drive and not to skip to the 2nd HDD if the 1st struggles to spin up in time.
#10
kester76
athunder
kester76
Are you shutting down the PC or is it going into a sleep cycle ? Removing the PSU cable will cause a full power down and reset if it's in a sleep cycle.
I shut it down, although I don't normally wait around to check, last night shut down ok, and this morning boot up fine again. Seems a very intermittent fault, maybe it was that power cable to the drive.
I think your confusing things here with a dead PC and a PC that doesn't boot. A dead PSU/faulty wont get past POST and may spin fans and power CDROMs etc but no POST. It sounds like your PC is posting but it isn't booting the HDD ?
I think your PSU is fine as any major issues with the 5v/12v rails and the PSU would be dead/standby and no way is that drive drawing too much power to boot. I would say that your HDD spin up time might be the issue or the drive could just be dying.
Make sure that you have set your bios only to boot your OS drive and not to skip to the 2nd HDD if the 1st struggles to spin up in time.

Yesterday when I posted this, pressing the power button did nothing, no lights, no fans, no beeps, nothing.
As of now, since using a different power cable to the SSD, everything is fully working(though I'm not convinced the problem won't come back).
#11
athunder
kester76
athunder
kester76
Are you shutting down the PC or is it going into a sleep cycle ? Removing the PSU cable will cause a full power down and reset if it's in a sleep cycle.
I shut it down, although I don't normally wait around to check, last night shut down ok, and this morning boot up fine again. Seems a very intermittent fault, maybe it was that power cable to the drive.
I think your confusing things here with a dead PC and a PC that doesn't boot. A dead PSU/faulty wont get past POST and may spin fans and power CDROMs etc but no POST. It sounds like your PC is posting but it isn't booting the HDD ?
I think your PSU is fine as any major issues with the 5v/12v rails and the PSU would be dead/standby and no way is that drive drawing too much power to boot. I would say that your HDD spin up time might be the issue or the drive could just be dying.
Make sure that you have set your bios only to boot your OS drive and not to skip to the 2nd HDD if the 1st struggles to spin up in time.
Yesterday when I posted this, pressing the power button did nothing, no lights, no fans, no beeps, nothing.
As of now, since using a different power cable to the SSD, everything is fully working(though I'm not convinced the problem won't come back).
Sounds more like your power switch is faulty. A PSU will always produce low power when switched on so that motherboard light will be lit, even a damaged PSU will pulse the fans when the power switch is shorted.

Unless that molex/sata power connector is shorted it will make no difference on the PSU.

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