Dead computer after accidental PSU removal attempt while power cables connected

[ManWithCamera]

Hi guys!

While Z820 being opened (the computer was turned off), I did not notice that the power cable was connected and tried to remove the power supply from the case. The power supply started up at the moment (PSU fans started twisting), so I turned it off, but when I try to restart, the computer no longer wakes up. The LED indicator on the back of the power supply is on, but that's it - no disk activity, no boot attempt.

Has anybody experienced such a problem? How to check (without additional, working PSU) whether it's a problem with PSU or MOBO? Is there any chance to get an electrical scheme of Z820 1125W PSU? In case I'll try to find working PSU to check mine - should it be exactly the same 1125W PSU or could I also use 850W PSU for checkout (my mobo has two E5-2687W v2)?

Thank you in advance for all the support.

[DGroves · Accepted solution]

with the power cable disconnected, open the side panel and press the cmos reset button for 3 sec

now leave the power cable disconnected for 72 hr, then reconnect and the system should behave normally

now boot, enter the bios and set date/time and any other necessary settings

if you have the stock 850 watt supply you can use it as a quick test unit to see if you can get to the bios, but don't enter windows with it

[ManWithCamera]

BINGO! after BIOS resetting (I skipped 72 hours waiting) my computer is alive and kickin' again 😁

DGroves - thank you very much!