just found this:"The power supply used in the Power Macintosh G3 Desktop is not the same as the power supply used in the Power Macintosh G3 Minitower and Macintosh Server G3 computers.
If the logic board is installed in the Minitower/Server chassis, the power supply jumper must cover the pins marked çPS. If the logic board is installed in the Desktop chassis, this jumper must cover the pins marked çMac. (Replacement logic boards should come preset for the Desktop model.) When replacing the logic board, be sure to check the power supply jumper setting. If this jumper is missing or set incorrectly for the computer model, the computer will fail to boot.
These logic boards include a removable processor module, aka a ZIF (Zero Insertion Force) module. This module can be replaced in the event the stock processor module fails, or to upgrade to a faster processor.
Processor modules are shipped with the appropriate jumper configuration block to place in location J16.
When replacing the processor module, you must change the processor jumper block and warranty sticker to be compatible with the processor module you are installing. Failure to install the jumper block properly will result in a unit that fails to boot.
The voltage regulator module regulates the voltage for the particular processor used in different Power Mac/Server G3 systems. The voltage regulator provides an easy way to regulate voltage without changing specific resistor values on the logic board. When you replace the logic board, you must transfer the voltage regulator from the old logic board to the new one. (Note: Always try replacing the voltage regulator to resolve power-on problems before replacing the logic board.) "
