Chosen Solution
I Have a 2017 imac 21.5”, won’t turn on at all, no drives, no fans, nothing. I have taken the screen off and there are no diagnostic LEDs coming on at all. I have measured the voltages on the PSU as follows (all wrt the upper most pin on the larger connector: [larger connector] v ref 0v 0v 12.1v 12.1v 12.1v [smaller connector] 3.32v 0v 0.01v 0.02v 0v 0v does this indicate a dead PSU? I’m hoping it’s the PSU rather than the logic board!
Yes, you need a new PSU. Depending on what happened the logic board might have gotten damaged as well. Do you have a good surge suppressor or better yet a UPS, and have all of the peripherals plugged into the suppressor or UPS? A surge or lightning strike can have done you in.
