Z6 G4 - Won't properly power on (on then immediately off)

[Casper042]

I was given an HP Z6 G4 because it won't boot.         

When you plug in the power cable, the machine attempts to power on shortly after but there is a click and it immediately powers off.         

Green BIST light on PSU lights up only for that brief 1/2 second period and then remains off.

Stripped out all option cards and disconnected all drives, etc, same problem.

Disconnected P1 and P2 from System Board, plugged power cable back in, and now BIST LED remains green.

Just wondering 2 things

1) Does this sound like System Board? Or could it still be PSU?           

2) On ATX PSUs you can jump 2 specific pins to emulate ATX Power On command to test PSU outside of PC, is there something similar for these HP 1000W proprietary PSUs? (ATX is Green to Black, Pin 4 to 5, but P1 and P2 here use all black wires)

Hoping to narrow issue down before I throw any money at the problem.

1WU32UT#ABA is the specific PN on the top.

Thanks,

Dan

[SDH]

Dan,

Over the years I have found this type of situations is usually fixable with a motherboard transplant... it is more common for one of those to go bad than a power supply.

That is a valuable workstation and I'd probably try a new-to-you power supply first if you can find an inexpensive one on eBay because having a spare one of those in the garage is nice insurance and testing that out first is fast. However, I bet a motherboard transplant will fix you.  I'm guessing Clint Eastwood would advise that too... depends on if you're feeling lucky today.