Hi there. I recently repaired my little iMac changing the Flyback transformer and a little Potentiometer which is for adjusting the B+ voltage for it. I'm by no means an expert, just an amateur electronics guy. I got the hint from a german technician and would recommend everyone to try just replacing this potentiometer for some more robust CERMET type. Here is the Post for anyone interested: https://www.macuser.de/threads/imac-dv400-crt-problem.110173/ So the mac works again but now it's missing working Firewire ports! First i thought that maybe it only needs a PRAM reset...a NVRAM reset...PMU reset...Cable?...Nothing! I can't find a schematic for my iMac G3 but i found the Datasheet for the Firewire chip. I will attach it also here for references. Maybe someone could guide me through what i could check for or provide a schematic for the motherboard. Thanks a lot!