I have two Pegasos II systems and on one of them it seems that the G4 CPU card has problems. I've isolated the problem to the G4 CPU card as I've swapped components between both Pegasos II boards.
The problem seems to have happened when the CPU fan was noisy, so I removed the CPU card, cleaned the fan and put it back. The fan didn't work. Then I checked and one of the the power wires was old and disconnected from inside the fan. I fixed that and it was spinning OK again. However, the Pegasos II always displays a blank screen. I swapped the CPU card from my other Pegasos II and it worked fine.
I think I might have fried my card? I am pretty handy with electronics, so if it is something I can check (capacitor changing, etc), please let me know if any of you have any tips.
I'm yet to connect to it via serial.