Faulty Power Supply ?

[Vikki Sixx]

OK, tried it with the PSU connected with the bridge trick and the CPU fan runs, however there is a weird "ticking, pulsing" sound and the power supply LED on the back flashes (does not stay steady on)

 

[Vikki Sixx]

I am turning in for the night, please reply with any other ideas if you are still awake. Thanks for all the help so far .... very informative. Good night

 

[Swa]

You bridge the 24-pin while connected to the MOBO ... is there no chance of damaging the MOBO then?

If done incorrectly. The power button connects the same two wires so current simply flows through the wire instead of the motherboard. If it does blow it was probably faulty already. Chances are higher a faulty mobo can blow the PSU. Otherwise the safer option would be to bypass the on button and bridge those two connections instead.

 

[Swa]

Sounds like something is drawing more power than it can handle. Did you add anything recently like a gfx card? If not one of the PSU transformers could have died but since it does the same with the other PSU it sounds like it's the mobo. Last resort would be to disconnect everything else. It should beep with the speaker connected. Then add back starting with cpu and ram.

 

[chrisc]

Measure yellow to black with a meter = 12 vdc. Measure red to black = 5 vdc. If anything else, chuck.

 

[Vikki Sixx]

Sounds like something is drawing more power than it can handle. Did you add anything recently like a gfx card? If not one of the PSU transformers could have died but since it does the same with the other PSU it sounds like it's the mobo. Last resort would be to disconnect everything else. It should beep with the speaker connected. Then add back starting with cpu and ram.

Will try this .... it seems as if all the fans now spin silently, so where could the humming sound have come from? Is it possible the CPU fan was not working 100% and now the CPU is damaged ?

 

[TJ99]

Will try this .... it seems as if all the fans now spin silently, so where could the humming sound have come from? Is it possible the CPU fan was not working 100% and now the CPU is damaged ?

A lot of things are possible but you need to be clearer. At first you said the PC wouldn't turn on at all. Then you seemed to suggest it is turning on again but making a noise, which is why I suggested stopping the CPU fan. So:

Is it (the PC) turning on at all now?
Are all the fans working?
Is it making some noise?

 

[Vikki Sixx]

A lot of things are possible but you need to be clearer. At first you said the PC wouldn't turn on at all. Then you seemed to suggest it is turning on again but making a noise, which is why I suggested stopping the CPU fan. So:

Is it (the PC) turning on at all now?
Are all the fans working?
Is it making some noise?

Ok, let me be clearer:

1 - PC does not turn on at all
2 - PC was making a strange sound over the last few weeks, but was working fine
3 - I have stripped the PC so that there is only a motherboard with the case connected to it (speaker, switch, etc)
4 - Still can not turn the PC on via the front switch
5 - If I bridge the terminals (with both the 24-pin and the 12VDC cables connected, the PSU will go on, but no beep

Shall I start putting back all the other bits and pieces and start seeing if there is any difference ? or does it sound like a MOBO problem ?

 

[Vikki Sixx]

Also tried the following with the following results :

- Connected PSU (600W) and CPU fan only to MOBO (no RAM, HDD, Media, GFX or CPU present)
- Bridged terminals
- turned power on at wall socket
- pulsing sound is heard
- large Green LED on the MOBO flashes
- CPU fan turns continuously

Then using my spare 450W PSU :
- Connected PSU (450W) and CPU fan only to MOBO (no RAM, HDD, Media, GFX or CPU present)
- Bridged terminals
- turned power on at wall socket
- NO pulsing sound is heard
- large Green LED on the MOBO stays ON
- CPU and PSU fan turn on for a moment (2 sec) then stop

 

[NomNom]

If you are in Durban I have a PSU you can test it with. Otherwise I'm thinking motherboard or PSU, but leaning more to PSU's.

 

[Vikki Sixx]

If you are in Durban I have a PSU you can test it with. Otherwise I'm thinking motherboard or PSU, but leaning more to PSU's.

Thanks for the offer ... I am in Nelspruit

Why do you thing PSU ? The bridge trick worked on both PSUs and with either PSU connected in the normal fashion, the PC does not turn on at all ...

 

[NomNom]

Thanks for the offer ... I am in Nelspruit

Why do you thing PSU ? The bridge trick worked on both PSUs and with either PSU connected in the normal fashion, the PC does not turn on at all ...

Because when you connected the different PSU's the motherboard displayed different symptoms, don't get me wrong it could still be the motherboard, I just find it strange that when you changed the PSU it displayed different symptoms, if it was the motherboard I would think that it would do exactly the same thing no matter what PSU was connected.

Did you check the motherboard for bulging caps?

http://www.pcstats.com/articleimages/200302/capblown_3.jpg

http://ww2.justanswer.com/uploads/hongkongpom/2010-08-24_114342_2010-07-19_161942_bulgingCap1.jpg


Hold on a sec you didn't have the RAM connected in both cases and the motherboard didn't beep at all? is there a PC speaker connected to the motherboard? If there is then it should beep because of there not being RAM installed.

The problem though is in the 600W PSU test the PC speaker should of Beeped due to not having RAM, if it didn't do anything it could indicate that the motherboard is dead. But in the second test with the 450W PSU there wasn't enough time for the PC speaker to go off which could indicate that the 450W PSU is faulty.

To make sure it's the motherboard I would get a 3rd PSU from somewhere.

Also just to make sure, in both tests you did remember to connect the 4 pin power connector to the top of the motherboard for the CPU correct?

 

[Vikki Sixx]

The problem though is in the 600W PSU test the PC speaker should of Beeped due to not having RAM, if it didn't do anything it could indicate that the motherboard is dead. But in the second test with the 450W PSU there wasn't enough time for the PC speaker to go off which could indicate that the 450W PSU is faulty.

The PC speaker did not go off in any instance, with the 600W or the 450W. The difference was that the 600W kept pulsing (big Green LED on MOBO was flashing) while with the 450W the power was on (big GREEN LED always on)

Very confusing.

Machine is 3 years old so maybe I should buy components and hence start building a new PC. Start with PSU or MOBO ?

 

[Alton Turner Blackwood]

Sounds like your PSU is a goner. Remember just because a PSU goes on and spins doesn't mean its working. Different rails (if it's multi railed) power different components and some rails might work and some not.

 

[Vikki Sixx]

Sounds like your PSU is a goner. Remember just because a PSU goes on and spins doesn't mean its working. Different rails (if it's multi railed) power different components and some rails might work and some not.

But the PC doesn't work with either PSU - the 600W and the 450W

 

[riscbroker]

But the PC doesn't work with either PSU - the 600W and the 450W

As per chrisc4290 - check the output voltages, on both PSU's. Get an accurate multimeter and make sure all the output voltages are present and within spec.

 

[TJ99]

Ok, let me be clearer:

1 - PC does not turn on at all
2 - PC was making a strange sound over the last few weeks, but was working fine
3 - I have stripped the PC so that there is only a motherboard with the case connected to it (speaker, switch, etc)
4 - Still can not turn the PC on via the front switch
5 - If I bridge the terminals (with both the 24-pin and the 12VDC cables connected, the PSU will go on, but no beep

Shall I start putting back all the other bits and pieces and start seeing if there is any difference ? or does it sound like a MOBO problem ?

Doesn't help much unfortunately, it could be the PSU or the motherboard.

Also tried the following with the following results :

- Connected PSU (600W) and CPU fan only to MOBO (no RAM, HDD, Media, GFX or CPU present)
- Bridged terminals
- turned power on at wall socket
- pulsing sound is heard
- large Green LED on the MOBO flashes
- CPU fan turns continuously

Then using my spare 450W PSU :
- Connected PSU (450W) and CPU fan only to MOBO (no RAM, HDD, Media, GFX or CPU present)
- Bridged terminals
- turned power on at wall socket
- NO pulsing sound is heard
- large Green LED on the MOBO stays ON
- CPU and PSU fan turn on for a moment (2 sec) then stop

What pulsing sound? Where is it coming from? What motherboard is it?

It sounds like the 600W PSU might be working fine, the other two are busted. It's also possible all the ones you've tried are busted, especially if it's no-name brand stuff.

I'd recommend trying it with a power supply that you know to be working.

 

[NomNom]

I'd recommend trying it with a power supply that you know to be working.

Agreed, best way to figure this out.

 

[Vikki Sixx]

Agreed, best way to figure this out.

I know for a fact that the 450W PSU has never been used. It came with the tower case that I bought and I imediately changed it for the 600W PSU .... so not so sure

 

[Vikki Sixx]

As per chrisc4290 - check the output voltages, on both PSU's. Get an accurate multimeter and make sure all the output voltages are present and within spec.

Is it only the 12VDC and 5VDC that must be checked on the 4-pin connector .... what must be checked on the 24-pin connector ?