Mac Pro 5,1 does not power on - No Power/Dead Unit?

Hi, I'll start by stating that I've been searching through several related threads, and have also done a diagnostic deep dive with the help of the official 5,1 technician guide from apple. I'm posting because I'd like to get some input from the community before proceeding forward - either confirmation that I'm approaching this correctly or suggestions to try something differently. Your help is appreciated.


Problem:
Mac Pro 5,1 (2010) won't power on. When I plug in the power and press the power button, I immediately get a few quick clicks coming from the PSU, and that's it - no fans spinning, no other noises, no chime. This all started right after I attempted to install a Sonnet Allegro x5 port USB 2.0 PCI card (purchased used from OWC mac sales) into the uppermost PCI x4/RAID slot.


Troubleshooting so far:
Pt I. Removed Allegro PCI card, reset SMC - nothing.

Pt IIa. Followed No Power/Dead Unit troubleshooting steps in apple's mac pro 5,1 technician guide. Checked secure PSU connection to backplane board, as well as connections to processor tray and front panel board - OK. 5V STBY LED lights up amber when DIAG LED pushed - OK. With front panel board disconnected, mac pro does not power on when SYS PWR is jumpered together, just same quick clicks from PSU. Moved to minimum configuration testing, as suggested.

Pt IIb. Disconnected HDDs, super drive, processor tray, graphics card, airport, bluetooth, 3V battery, PCIe fan, processor cage + fans and speaker, front panel board, and all other connected cables (only backplane + PSU left connected). OVTMP CPUA/B LEDs quickly flash red once when power is connected - OK. 5V STBY lights up amber when DIAG LED pushed. Processor cage + fans, and processor tray reinstalled (without CPU, heatsink, northbridge heatsink, and memory). 5V STBY/DIAG LED still OK. SYS_PWR jumpered still does not power on mac pro (indicated by idle fans and nothing else occurring in response), just same quick few clicks from PSU. Unsure what else I can do for troubleshooting at this point.


Assessment:
+Backplane board shot. Maybe static from the POS USB PCI card I just purchased. Also while I did pull the power on the Mac Pro to install it initially, I did not pull plugs on any of the peripherals (USBs, video cable, audio cables) - static here? I've never experienced this, esp I'm on a laminate flooring and the mac pro sits on a composite shelf board.

-PSU unlikely? The quick clicking response to attempts to power on seems normal operation. PSU does not emit any unusual smells. CPUA/B LEDs light up and 5V STBY LED lights up when DIAG LED pressed, indicating power to board.

-Processor tray unlikely? Jumpering SYS PWR without the tray yields no response (expected); jumpering while processor tray is inserted yields the PSU clicking, meaning the system recognizes the tray.


Plan:
Find other ways to reset the board, if that's all that is needed...
Otherwise, purchase a used backplane board.
I have a Genius Bar appt this upcoming Thu to get a dx only, but idk how experienced they are with pre-2012 MPs.

Please let me know what you think about what's going on, if there's anything else I can try, or if you think I should just already go ahead with finding a new board.

Thank you,

My guess is your PS has either failed or partially failed. All the symptoms you stated point to that. I've been working on electronic equipment for years including consumer electronics and some very sophisticated government equipment and in all those years have only seen a static failure maybe twice.

I would be interested in hearing what the genius bar found during their diags. Let us know.

Thanks for your response. I kind of hope it is just the PSU - I think it would be a simpler fix. I'm going to visit an Experimac today and see what they can tell me as far as dx goes. I figure I may not have to go to the apple store this Thur if I can get a solid answer earlier.

Be careful about using other than a genius bar to run diagnostics on your Mac Pro. An Apple genius bar will not charge for the diagnostics, however, other authorized Apple service centers will probably charge a fee and in my opinion they're not as technically equipped. Yoy might want to wait and use an Apple Store. Make an appointment with them first. Let us know how things turn out.

Hi, so I ended up having it diagnosed at Experimac instead of the Apple Store, and it was confirmed to be the PSU. I was able to purchase a used one off ebay (same exact model PSU) and install it last week. System running, things are back to normal.

Although, Experimac seemed to know what they were doing, you made a good point. I'll still try to exercise care next time, and err on the side of caution. Thank you for your help!

Glad to hear you're back up and running. Mac Pro power supplies seem to be the weak link in a very well designed machine. Thanks for letting us know.