Diagnostic LEDs (4th red)
Got this system in today.
Heres the issue: When you first turn it on and it works fine. After a second boot (eg, reboot) it fails to boot after the startup chime. Works fine if you leave it unplugged for half an hour and then try.
Heres what happens when you start it up a second time:
- LED 1 green
- LED 2 green
- LED 3 Off
- LED 4 Red
- LED 2 turns off
Fans speed up and are cut off by shutdown.
Update (05/06/2018)
Okey Doke. I replaced the Thermal Paste on U22 and on the CPU, it works like a charm!
iMac G5 17" Model A1058 Logic Board Replacement
Hope this helps someone else.