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David analysis is right. The 12v back feeded to the psu own 5v damaged something inernally, now the psu try to turn on, but internal monitor circuilt shut itslf down when try to power on. I got no reading on 5v and 3v, but 12v has split second of power, then shut off itself as i turn the power on. I saw the fan span for a few seconds The power supply then will not turn on again until it reset a few minutes later. So, the question is if this possible an easy fix? if yes, i will open them up...if not, then i may RMA them.....

David analysis is right. The 12v back feeded to the psu own 5v damaged something inernally, now the psu try to turn on, but internal monitor circuilt shut itslf down when try to power on. I got no reading on 5v and 3v, but 12v has split second of power, then shut off itself as i turn the power on. I saw the fan span for a few seconds The power supply then will not turn on again until it reset a few minutes later. So, the question is if this possible an easy fix? if yes, i will open them up...if not, then i may RMA them..

Hi,
Anybody has experience repair PSU burned out due to connect to EVGA molex/sata cables. I know the cable is not compatible (i got them mixed up), but I though i can connect it and use a PSU tested to find out which is the wrong sata/molex cables. As soo as I pluged in the powered molex cable to the PSU tester, the power supply short out, and will not turn on anymore. After the incident, the PSUs (both HX1200 and C850) try to power on and shut itself off immediately. The ATX PSU tester survice the short circult, still working perfectly. Anybody know if it's an easy fix or know which parts...