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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?
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?
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.