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Bad PSU shorting out MOBOs

Last response: in Motherboards
August 10, 2010 7:36:55 PM

Has anyone had experience with a shorted power supply destroying a MOBO? I removed a PSU from a dead computer and installed it to a known good computer. Now that computer sounds like it's running as soon as I plug the power cord into it (without pressing the power button) but otherwise is dead- no video or anything.

More about : bad psu shorting mobos

a c 104 ) Power supply
a b V Motherboard
August 10, 2010 7:47:37 PM

not had it myself, but its very possible,
I would've tested the psu in question on its own,not put it in a working unit though
August 10, 2010 8:39:32 PM

I've never run across this problem before and I don't recall reading about anyone else ever having it. Online searches haven't helped much either- apparently it's a very rare problem. I tested the original computer with a known good PSU and when it wouldn't start with that, I mistakenly assumed that the MOBO was the whole problem. Since we are short on spare PSUs and cash around here, I wanted to save the original PSU for other systems and wanted to make sure it worked before I saved it.

Using 20/20 hindsight, I did a multitester pinout test and one of the +5 volt pins read about 8 volts. That is several volts above tolerance and is probably what ruined the boards. I'm going to have to be more careful in the future. Fortunately, the systems I ruined are older systems that already had problems so it's not a huge loss but I would've liked to be able to fix them. Now that doesn't look like a feasible option.
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a c 104 ) Power supply
a b V Motherboard
August 11, 2010 6:15:43 AM

Sorry about that man, but if nothing else you've learned for future to get your multimeter out for psu problems first :)  may save a more expensive system from the same fate down the road :) 
August 11, 2010 2:56:23 PM

Yes, you are right. Also, A better name for the subject of this topic would've been: "Bad PSU RUINS motherboard" since it's not certain whether the PSU was actually shorted or whether its overvoltage caused a 'short' or an 'open' in the boards. Had I used a multitester before I posted, I would've given a more accurate subject line. Also, had I searched on line with the updated subject line (instead of using the search term 'shorts') I would've found this forum posting:

There I would've seen that this is a fairly rare, but not impossible, phenomena.
a c 104 ) Power supply
a b V Motherboard
August 11, 2010 5:49:45 PM

Yup, Its a double-edged blade that electrickery stuff :) 
Well, Were here for your next build if you need us man :) 
August 21, 2010 3:04:31 PM

Best answer selected by gbferrell.
August 21, 2010 3:05:31 PM

Thanks Moto
a c 104 ) Power supply
a b V Motherboard
August 21, 2010 3:43:30 PM

no problem man, thank you for B.a
August 21, 2010 4:12:44 PM

You are welcome.
August 21, 2010 4:13:41 PM

BTW, I don't see much progress on your Attempting to give a damn meter. Better reboot.
a c 104 ) Power supply
a b V Motherboard
August 21, 2010 5:48:48 PM

I saved it as a gif image (Fail hehe) originally,
you've inspired me to change it, should be working soon :p 
August 22, 2010 5:05:00 PM

I was only kidding, I hope you know, - don't change it- it's funny! :bounce: