820-3302 Wont start

[CRC2018]

Got an 820-3302 today - won't start up - there is one green diagnostic led - when I press the power button the fan spins a little then stops - no activity on any other diagnostic led's that I can see. Nothing immediately visible i'm wondering if this points to a PSU issue?

 

[2informaticos]

Q7950 fails a lot there.
Change it, just for test...

 

[CRC2018]

I can try that but I cannot find IRF6892 from a reputable supplier - is there an alternative available?

 

[CRC2018]

Actually I don't think it's Q7950 - I did try the SMC bypass mode and got the fan spinning on full and the voltage output of Q7950 was 12.2v on PP12V_S0 - that should indicate Q7950 is working?

 

[2informaticos]

Looks like Q7950 is good, if you get steady 12V_S0.
Just to confirm, do you get 22V at its Gate pin?

In SMC bypass, do you have USB activity?

 

[CRC2018]

there is no USB activity in SMC Bypass mode = also no display and no more diagnostic LED's light up. I'm getting 15v on the gate pin of Q7950 (tested at U7950) and yes there is stable PP12V_S0 in smc bypass mode.

 

[2informaticos]

I recommend to change Q7950, or at least U7950; +3V is not a good value for Vgs...

If board only turns on in SMC bypass mode, check the sensors output from page 48.

 

[CRC2018]

Gave up with this and got the customer another motherboard for $150.