I’m attempting to repair and old 2003 17” iMac G4 that won’t power on. It’s completely dead, no startup sound, fans don’t spin, nothing. I’ve tried the following so far:
- Attempted PMU reset using the button on the bottom (holding it in for 10 seconds). No change.
- Opened up the dome enclosure, 3.6v internal battery was intact but read zero Volts on a multi-meter so I replaced it with a new one. No change. PMU reset. No change.
- Tested the diagnostic pads on the bottom of the motherboard and get the expected 12v, 5v and 3.3v readings. Removed the PSU to check for bulging capacitors, all look perfect. Getting the expected 12v on the yellow lines. 3.6v on the blue line.
- Tried plugging in the unit while holding down the power button. Didn’t work for me but had apparently worked for someone on an iFixit forum.
- Tried warming up the PSU with a hair drier (as per a couple of YouTube videos), no success.
I understand that one can “jump start” the PSU to start it up by shorting some in the pins on the motherboard side power connector and I’d like to try this next to see if the PSU is working. Can anyone confirm how this can be done safely?
I also suspect that the previous owner might have crashed the PMU with successive reset attempts. I’ve read that this can irreparably damage some of the hardware and that some chips would need to be replaced. However, I’ve also read that this not true and crashing the PMU is not permanent (which makes sense to me).
Anything else I can try while I have all the parts laid out on the bench?
