Can a faulty motherboard fry a power supply?

[BZeto]

We have a lab of Dell Optiplex GX270's. These are notorious for having defective motherboards that eventually blow their capacitors and either stop working entirely or do crazy things that make the workstations very unstable.
Anyway, I recently replaced the motherboard in a system that was having problems. The mobo's capacitors were bulging and starting to leak. I installed the new board (that i got directly from Dell) and turned on the system, it immediatley started making a very high pitched noise and nothing appeared on the monitor. I thought it was strange so I unplugged the power and inspected the board to make sure everything was connected and seated properly, it was.

So I shutdown another computer that was running fine and took the power supply out. I put the power supply in the system with the new motherboard and started it up again. Sure enough the high pitched sound is still there. I unplugged power wires from everything but the 20 pin ATX and 4 pin to the mobo and turned it on again, same high pitch sound. This time the machine had been on long enough that I noticed a smell, an electrical burning smell. The sound is coming from the power supply as well as the burning smell.

That is 2 power supply's that have been borked (the one actually still tests ok so I dont think it was ruined, but the original PSU is dead) by just being connected to that system. Also, I know it isnt the power cord/surge protector/power outlet because I tried it in the lab and in my office which is in another building, same problem in both places. I have never seen something like this and my only guess is that the motherboard is causing something to short out.

Any input on this would be appreciated.

 

[oynaz]

a mobo frying a PSU is unlikely, but definitely possible.

 

[Safeway]

Bad caps can do anything they want. A short is the likely culprit, and would probably be enough to kill a cheap PSU.

 

[Jiggz]

Although this may be possible. PSU's do have safety features wherein if the output voltage fluctuates so far out of parameters it will trip or shut down. Other features also include overcurrent protection. Of course, there is always a possibility these safety features will fail and cause total failure of the PSU. The same is true with the mobo. It also has safety feature making sure power being fed is also within parameters. And of course, just like the PSU's feature, it could also fail.

Anyways, it'll be immaterial to test the new mobo now since it could have failed already. RMA it and before plugging, make sure you use a known working PSU.

 

[BZeto]

Well I've swapped out every part but the cpu and it still does the same thing, it has to be the motherboard. I have never seen something like this. Guess I'll get yet another replacement board.

 

[GalvanizedYankee]

I like what Jiggz had to offer.

If caps fail shorted the current can overload the VRM / FETs and in this case, the RAM or CPU can sustain damage. Caps most usually fail in an open state and nothing takes a hit.
Look for burn marks around the VRM / FETs and look for burns on the bottom of the mainboard.

Generally a failing PSU will drive board caps to early failure. Read http://www.badcaps.net/faq/
Topcat, the site Admin. has recapped hundreds of GX270 boards. You might consider registering over there and asking for further input.
You can not register with a free email service. Please give the referral to Galvanized if you register.

 

[Steve]

I know for a while Dell was using proprietarily wired PSUs, such that changing it out for a standard PSU or putting in an incompatible board would fry something. Is that the case here?

 

[BZeto]

Originally posted by: GalvanizedYankee
I like what Jiggz had to offer.

If caps fail shorted the current can overload the VRM / FETs and in this case, the RAM or CPU can sustain damage. Caps most usually fail in an open state and nothing takes a hit.
Look for burn marks around the VRM / FETs and look for burns on the bottom of the mainboard.

Generally a failing PSU will drive board caps to early failure. Read http://www.badcaps.net/faq/
Topcat, the site Admin. has recapped hundreds of GX270 boards. You might consider registering over there and asking for further input.
You can not register with a free email service. Please give the referral to Galvanized if you register.

I dont see any visible damage on the board whatsoever.
Also, I tested the RAM that was installed on another system and it works fine, I dont think it was damaged. Still unsure about the CPU.

Originally posted by: sm8000
I know for a while Dell was using proprietarily wired PSUs, such that changing it out for a standard PSU or putting in an incompatible board would fry something. Is that the case here?

Nope, all parts I'm using are from other GX270 systems and are original Dell parts.

 

[stevf]

how is your power service in your area? sounds like an awful lot of problems and perhaps the stuff coming out of the wall sockets has lots of surges/spikes/dips/sags

 

[Jiggz]

Just like you said, the original PSU is dead and it could have damaged your new mobo. Sure the second PSU was a known working PSU when you tried it but the mobo could have already been damaged by the first PSU. So it's safe to say the mobo or cpu is already damaged. Do you have ways to try the CPU? If you can try that CPU and it's working, I'll RMA the mobo.

 

[BZeto]

Originally posted by: Jiggz
Just like you said, the original PSU is dead and it could have damaged your new mobo. Sure the second PSU was a known working PSU when you tried it but the mobo could have already been damaged by the first PSU. So it's safe to say the mobo or cpu is already damaged. Do you have ways to try the CPU? If you can try that CPU and it's working, I'll RMA the mobo.

Before RMAing the original mobo I tested the PSU and it seemed fine. Guess it could have just been bad timing and went out when I put the new mobo in, but that seems unlikely.
Anyway, I received the 2nd motherboard and installed it with all the other original parts (including CPU and RAM), all is working fine. Thanks for the input everyone.