Ultra Power Supply

[Sparkie54]

Can someone please help me with repairing a PC power supply. My supply quit and I have been only partially successful. I found a burned out resistor on the board I replaced > a 5 watt 20 ohm and a bulging cap that I also replaced. When I try to power up now with the supply hooked up to a working pc the motherboard lights come on and I get a momentary turning of the fans and then it stops. The board lights still stay on and about every 15 to 30 seconds the fans again do a momentary spin and then stop. I tried to do some power test with a volt meter and did not have any power form the 12 volt rail and from the 5 volt rail I get about .02 volts. I did not test for the 3 volt rail though. I do not have a working knowledge of electronics but can do some minor test with a mulit meter and replace diods capacitors and resistors and such. Any help would be appreciated

Thanks Sparkie54

[thepastimer]

Have you checked the inverter?

[abel2b]

If you have some sign of power up, it has hope!!

You still have a short which the regulator ic is sensing replace all filter capacitors on the 5v,12v and 3.3v line even if they don´t have signs of leaks or bulging, cause they might just have an ESR problem, Check fast rectifier diodes ( transistor like components mounted on secondary side heatsink ) are not shorted, open or leaking, also is the large toroid transformer looking kind of burnt or dark, enamel insulation on the wires might have failed due to heat and are shorting , swap it from another broken psu or if you feel brave disasemble taking notes of wire size and turns and rewind it again...

also you might want to consider regulator ic is defective ???

Hope this helps !!

Good luck

Abel