[help] Powermac G3 Booting

I recently obtained a PowerMac G3 Yosemite, but it only boots when the case is open. Once it boots, if you close it, it shuts off!

None of the wires appear to be pinched and all connections appear to be clean.

Any suggestions?

You have a short going from the power supply to the motherboard.

Double check all the connections. I bet you will find one of the power cables is loose or on the verge of breaking off.

This is why Apple stopped attaching the motherboards to the case door.

Repeated opening and closing caused wear on the cables and stressed some of the connectors as well.