Faulty power supply?

Hi hopefully one of you guys can help after much messing around....

I have a fairly old but decent spec pc with a vs650 power supply.it stopped working. I have it starting up (fans lights etc) but no signal to monitor. Tried cleaning everything, removing ram, bios battery etc but still same.i have managed to get into bios/windows a couple of times then did a restart and it went into a boot loop.

I tested the psu with a voltmeter. Everything seems OK apart from BLUE wire on 24 pin connector. It's reading

-11.2v instead of - 12V. Not sure what this wire is??? Could it be the problem??? The power good is 3V also.

Any of you guys had a similar experience?

Thanks for help..

the blue wire is a minus 12v. The spec is pretty wide on this one, +-10% so it's okay.

 

The power good signal on the other hand should be +5V. If you only have 3V, something may be off on the PSU.

What voltages do you read for 3.3v, 5v and 12V?

Hi thanks for reply. Yes them voltages are all checking out within 0.1v. I read somewhere power good can be as low as 2.5v and up to 6v. Hopefully not a mobo problem. Don't know what else to try

Ah right.. the ATX design guide states 2.4 to 5V..

A bit at loss too.. But in theory, if the PC starts (power good OK), the PSU should be fine.

A guru is needed :p

Yeh I guess so. I'll try taking mb out case incase it's shorting.

It may be a circuit board problem, poor contact or damage, after all, the chip solder joints in the circuit board are sometimes worn out or fall off due to vibration.