@kalleboo Might very well be, that is a somewhat similar symptom to my PowerMac G5 before we replaced the PSU. Although yours flashes the LED and mine didn't (it would just turn it on, fans would shake, and turn off again). The old PSU passed the basic test (it had power on the pin the service manual recommends testing) but could not sustain the Mac working.

So I would start with that, after the basic things (remove RAM, cards, disk, everything, and try again with as little RAM as possible).

@kalleboo a few weeks ago i picked up a free PM G5 box someone was going to toss out.

last night i finally opened up the box. it had some documentation sitting at the bottom of the box, probably from when the owner had replaced their dying G4 with the G5.

i would not be surprised at all if this was a common failure point on the G4. (that, and those psu caps have to be just pooched after 30 years)

#macintosh #vintageApple