My son built a high end PC for producing and engineering his music. The PC has worked flawlessly for well over a year but then started to experience issues turning on (from front panel). Cycling the power switch on the 500B PSU or unplugging from the wall would sometimes allow it to successfully boot up from the front panel switch.
 
 
EVGA power supply model #: 100-B1-0500
Motherboard: AZRock Z97 Extreme
More PC info available if you need it.
 
I have found that when the PC is shutdown and the PSU switch is ON that there is a bias voltage available to the motherboard of ~3.3V. I can measure this on the motherboard where the front panel power switch connects. When cycling the PSU switch, the 3.3V rail doesn't always come up to 3.3V and this is when the PC won't start. A good PSU start up will yield ~3.4V at the motherboard and a bad PSU start up will only yield ~2.8V. Bad starts occur about 95% of the time but you can help start up by cycling the PSU switch to OFF then back ON quickly. I have installed a new BIOS battery thinking the old battery (down to < 2.4V) was dragging down the PSU 3.3V through a parasitic connection and that seemed to help just a bit (but PSU cycling still can fail).
 
Is there something I can fix or repair internally on the 500B PSU? Maybe a known internal issue?
 
Thanks
 
 

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