Dead PC - do I have a PSU or Motherboard problem ?

[CoolRunning]

Currently my PC is dead. Do I have a PSU or MB problem (or something else?)

The problem was progressive over about 5 days.
- at the beginning, it would crash (either black screen / frozen screen / screen tearing) after a short time, say 10 seconds to 2 minutes. A reboot might or might not fix it.
- 2 days later, the reboot would never fix it. But I did get memtest86 booting from CD and in a 2 hr run the memory was perfect.
- at that time I could usually boot into the BIOS, but now even that does not work.

Now, a boot shows:
- both fans OK
- CD light comes on and off for about 10 secs
- the screen remains black
- the the CD light goes off and then nothing
- there is no BIOS and no PC beep


System is homebuilt desktop with:
INTEL Kaby Lake Pentium G4560 3.5Ghz CPU, ASUS Prime B250M-A Motherboard & 8GB 2400Mhz Crucial DDR4 RAM
Using Intel graphics, no discrete graphics card
Ubuntu 16.04 LTS

I have measured the voltage on one of the spare disk cables and the 5 and 12 volt supplies look good.

Is it most likely a PSU or MB problem?

Your help very much appreciated.
What should I try next?

 

[mikeymikec]

Trying out a cheap and cheerful PSU should eliminate one possibility.

 

[VirtualLarry]

Ordinarily, I would probably say the PSU too. But on a G4560 rig, without a dGPU? That whole system is probably pulling under 60W. Pretty hard for even a bad PSU to screw that up, unless it's really, really bad. Still, wouldn't really hurt to try a new PSU.

Just for discussion purposes, OP, what PSU make and model and wattage are you using?

 

[CoolRunning]

Thanks Both

I agree, time to assume the PSU is the problem. When I did the upgrade in August I used the old PSU and it is a cheap, no name probably Chinese one, but reasonable wattage but it has no sticker so I cannot say.

I post again when it's done - the PSU swap.

 

[VirtualLarry]

So cheap, it doesn't even have a sticker? Yowza! Replace that immediately...!

 

[mikeymikec]

If it turns out to be the PSU, then if you can afford a half-decent one it's worth doing the research / asking here.

 

[CoolRunning]

Corsair 550 watt comes to mind - allows me to add a modest graphics card later.

 

[Campy]

This was on sale for $20 after rebate up until a couple days ago, but with the current price something like this Seasonic unit is better due to 5 year warranty.

 

[CoolRunning]

Thanks campy but I am in Europe. Things cost more here !

 

[CoolRunning]

I tried with an old PSU that I had, but the P4 connector (the one with just 4 pins in a square) is different.

So I have ordered a 550 watt Corsair from Amazon.

With Xmas coming, it will not be the usual quick delivery.

 

[Ketchup]

Any updates?

 

[CoolRunning]

Yes (update) and no (progress).

I have the new Corsair PSU and it is plugged in but the PC remains 100% dead.

All internal devices are detached (drives, cards etc) but jumpers etc are still in place.
I apply the power, use the PC power switch, the PSU and CPU fans turn, and then nothing. No beeps, no BIOS display, no lights on the KB. Nothing.

But the power off switch works after about 4 seconds. (I wonder where the timer is?)

Any ideas? I assume the memory is good (see my earlier post)

What can I try?

 

[Ketchup]

Have you tried running the system on just the basics? Only a keyboard and a screen, 1 stick or RAM, no other USB connections, no drives, etc.

Also, make sure there isn't a loose motherboard screw or anything under the board that could be causing a short.

 

[CoolRunning]

The PC only has 1 8MB memory stick and this is the one I tested earlier. No USBs, drives, cards connected.

I tried again without the mouse, no change.

I even tried without the KB. Still dead.

As for checking under the MB, I need more light. I'll try in the morning.

 

[CoolRunning]

I checked under the MB - nothing there.

 

[Iron Woode]

looks like it might be a dead motherboard.

however, did you try bench testing it? that means testing it outside the case on a non-conductive surface? could try another cpu if you have a spare one.

more than likely the mb is dead, though. RMA with Asus could be interesting.

 

[William Gaatjes]

Yes (update) and no (progress).

I have the new Corsair PSU and it is plugged in but the PC remains 100% dead.

All internal devices are detached (drives, cards etc) but jumpers etc are still in place.
I apply the power, use the PC power switch, the PSU and CPU fans turn, and then nothing. No beeps, no BIOS display, no lights on the KB. Nothing.

But the power off switch works after about 4 seconds. (I wonder where the timer is?)

Any ideas? I assume the memory is good (see my earlier post)

What can I try?

What you can try.
Try removing the power first by fully disconnecting the mains side of the psu and wait 30 seconds.
Take out the coin battery and measure it with your voltmeter. Should be 3V.
If the battery is 3V. place the battery back.
After that, erase the bios settings according to the manual by shorting the CLRTC 2 pin jumper.
Remove the short.
Power up the system by connecting the mains supply again.
Hopefully your motherboard will start.

Sometimes when the bios settings are corrupted and/or the coin battery is almost empty , the board will not start and seem dead. I have experienced that twice.

 

[CoolRunning]

I was wondering if my PC speaker was not working.
I took out the 8GB memory card, and got repeated beeps, 1 long then 2 short.
Just what one would expect for ASUS BIOS beep codes.
I put back the memory, try again, silence.

I will try the 2 above posts later today.

 

[CoolRunning]

I followed Iron's advice above

Bench testing - out of case tests
- nothing connected except power and internal jumpers. No video etc.
1 small beep, pause, 1 loud beep

- as above + VGA video.
similar beeps (cannot be certain, did not note), screen message saying 'no KB'
Bios on screen !

- as above + KB + mouse + boot-able USB
All works as expected, boots into USB !

So what is the problem? Is it a short to the case somewhere?

I can:
1. Leave out of case and do test with HDs - seems unnecessary
2. Be optimistic and put everything back in the case?
3. try something else first?

 

[Iron Woode]

I followed Iron's advice above

Bench testing - out of case tests
- nothing connected except power and internal jumpers. No video etc.
1 small beep, pause, 1 loud beep

- as above + VGA video.
similar beeps (cannot be certain, did not note), screen message saying 'no KB'
Bios on screen !

- as above + KB + mouse + boot-able USB
All works as expected, boots into USB !

So what is the problem? Is it a short to the case somewhere?

I can:
1. Leave out of case and do test with HDs - seems unnecessary
2. Be optimistic and put everything back in the case?
3. try something else first?

good to see the problem is with the case.

did you check the case for anything odd? any standoffs not in the right place? they might be contacting the mb.

you should check to see if it loads windows.

I am running out of ideas.

 

[CoolRunning]

I have waited for a while to be certain.

The problem has gone away. And I do not know why.

I reassembled everything and it all works.
- was it the PSU and when I got the new one and did my first tests I did something wrong?
- was it a short to the case that somehow resolved itself when I reassembled it?
- was it a bad contact somewhere ?

I probably will never know, unless the problem comes back.

Thanks everyone for the advice.