Från Apple service source "powermac_g4.pdf" som hittas här :
Sidan 22
Power Supply Verification
To start up, the Power Mac G4 logic board requires a “trickle”
power of +5V for AGP and PCI models, +28V for Gigabit Ethernet/
Digital Audio models, or +25V for QuickSilver models. If the
system fails to start up, follow the procedure outlined below to
determine whether the problem is related to the power supply.
Notering: jag modifierade ett MDD-nätagg (ger +25V) till min förra G4:a (gigabit e-net) och detta fungerade.