Question I killed my PC

Mar 22, 2021
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I was swapping out a faulty hard drive the other day when suddenly my PC stopped powering on. This is the system:

ASRock Z390 EXTREME4 Motherboard
Corsair CX750M PSU
Gigabyte GeForce GTX 1660 6GB Graphics Card
4x16GB Corsair DDR4 Vengeance LPX Black RAM
And various hard drives

This is what I tried so far.

PSU removed and tested all pins of the power rail. All produced the correct voltage.
Power rail pins 14/15 shorted and PSU fan powered up beautifully
Removed the HDD I installed.
Removed the PWR_BTN and shorted the pins
Put the RESET switch on to the PWR_BTN pins
Removed all RAM and added one-by-one
Checked visually for blown components.

What I do have is the pulsating green LEDs on the motherboard so I know something is working.

Ideally I don't want to strip every component off the board. When I say there is no power, the PSU fan does not even start spinning. It is totally unresponsive. But I know it works.

If anyone has any ideas that would be great.

Otherwise my next steps are to remove and reset all components starting from bare minimum (CPU basically). Then I guess replace the mobo.
 
possibility you shorted something on the board when changing drives. to troubleshoot this you would need to start by following NightHawk's suggestion.
having a similar system available to test your components in may make this much easier. if you have a friend, family member, etc with a similar setup.

or you may have knocked the main 24-pin connector or something else loose.
try reseating all cables and cards to the motherboard, and the PSU if it is modular.

to test RAM you should try each stick individually in each DIMM slot one at a time.
you never know which stick or which slot may have malfunctioned.
 
Mar 22, 2021
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Sounds good. I'll give it a go. I would have thought though that at least I would have got the PC to boot to at least some stage, even to the BIOS.
 
Mar 22, 2021
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If the PSU fan isn't spinning either

  1. psu failed
  2. something is tripping a protection
  3. nothing is telling it to turn on
PSU should be fine because I tested the voltage. When I connected pins 14/15 manually it powered on and the fan spun up. It's only while connected to the mobo that it doesn't do a thing.

I also shorted the power pins which I assume is the signal to turn on.
 
Mar 22, 2021
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OK I have stripped it bare. All it has is the CPU and one stick of RAM (also tried with no RAM). And no power to anything.

So I guess its either the motherboard or the PSU. And PSUs are cheaper so I'll try that first.
 
Mar 22, 2021
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I am having another think. I tested the PSU again and I am getting perfect voltages from the pins. It must be something on the motherboard, either not sending the on signal or something else. I am going to look in to a new motherboard. Annoying as this one is only a couple of years old.
 
Mar 22, 2021
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A PSU giving voltages when connected to nothing/under no load is not the same thing as 'PSU must be good'; far from it.

It could still easily be the PSU. (Alas, whichever you choose....it will, of course, be the other) :)

So PSU could give good readings and still be bad?

Yep, bound to be the other!! haha
 

Blackink

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Apr 27, 2014
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I have ordered a new PSU. I hope that will fix it.
Good Luck.
I had a PSU problem where the lights on the mobo would light up but the computer would not boot to Windows.
Took it down to a PC repair shop and sure enough, it was the PSU.

When I looked up that powers supply as to when I purchased it, it was 5 years and 3 months ago and the warranty was for 5 years!! Talk about being spot on for a life length.

So power supplies can be deceiving....
 

Karadjgne

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Breadboarding is 1 stick of ram in A2, cpu, cpu cooler and 2x power plugs. That's it. No monitor, no gpu, no mouse, nothing else. That's the absolute minimum necessary to pass POST.

Before plugging in the psu, short the cmos pins for a couple seconds.

If the psu/cpu fan fails to spin, you have 1 of 3 issues. Ram (which can be switched out), psu or motherboard. That's it. As broken down as it can be.

It's not unusual for external inputs/outputs such as hdmi cables or even keyboard/mouse wiring to develop a short, which will trip the psu protections and necessitate physically unplugging the psu and allow it to reset.

If it does spin, start adding stuff 1 at a time, rebooting in between, until it fails again. Save boot drive for last. If you don't do 20-30 reboots, you skipped steps. Like plug hdmi in and not the monitor, that's 2 things.
 
Mar 22, 2021
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Breadboarding is 1 stick of ram in A2, cpu, cpu cooler and 2x power plugs. That's it. No monitor, no gpu, no mouse, nothing else. That's the absolute minimum necessary to pass POST.

Before plugging in the psu, short the cmos pins for a couple seconds.

If the psu/cpu fan fails to spin, you have 1 of 3 issues. Ram (which can be switched out), psu or motherboard. That's it. As broken down as it can be.

It's not unusual for external inputs/outputs such as hdmi cables or even keyboard/mouse wiring to develop a short, which will trip the psu protections and necessitate physically unplugging the psu and allow it to reset.

If it does spin, start adding stuff 1 at a time, rebooting in between, until it fails again. Save boot drive for last. If you don't do 20-30 reboots, you skipped steps. Like plug hdmi in and not the monitor, that's 2 things.

So I unplugged everything apart from CPU and 1 stick of RAM. I shorted the CMOS. Still no sign of any power. I tried different stick of RAm in different slots. Still nothing. I guess nothing left now but to swap out the mobo?
 

Blackink

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Apr 27, 2014
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So I unplugged everything apart from CPU and 1 stick of RAM. I shorted the CMOS. Still no sign of any power. I tried different stick of RAm in different slots. Still nothing. I guess nothing left now but to swap out the mobo?
Jeeze...what's left?!?
One thing catnap3000 said about bread boarding is to use no monitor....how will you know the computer made it to BIOS?
I always bread board my new builds and I always have a monitor connected to see the BIOS screen upon start up.
 
Mar 22, 2021
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Jeeze...what's left?!?
One thing catnap3000 said about bread boarding is to use no monitor....how will you know the computer made it to BIOS?
I always bread board my new builds and I always have a monitor connected to see the BIOS screen upon start up.
I know it didn't make it to the BIOS because the PSU does not power up. the fan does not spin up at all. And it is not a zer-speed fan model. When the PC powers on the fan spins up. So it looks like the PSU is not getting a power on signal, or something is shorting it. But it literally does not do anything at all.
 
Mar 22, 2021
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Well I have today fitted a new motherboard (everything else the same) and the PC is back to life :) I don't know what I did to break it, I guess just bad luck and a costly one at that.

Thanks for all the support.
 

Blackink

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Apr 27, 2014
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So all of what you did came down to a new mobo just from swapping out a hard drive??
I wonder what could have caused a motherboard to go bad from swapping out a hard drive....

Glad you're up and running again!
Let's hope you're good for awhile now.
 
Mar 22, 2021
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So all of what you did came down to a new mobo just from swapping out a hard drive??
I wonder what could have caused a motherboard to go bad from swapping out a hard drive....

Glad you're up and running again!
Let's hope you're good for awhile now.
Yep. Weird. Never happened before, hopefully won't happen again.
 

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