2158-Aptiva - System Board Jumpers and Connectors
The blackened pin of a jumper represents pin 1.
When checking voltages, the power supply fan must be running.
To power-on the power supply without using the on/off switch, use a screwdriver
or other tool to short the connector CN2 pin 10-20 (with the switch cable
disconnected from the connector on the system board), or use a connection (jumper) to
short the black and green wires of the 20-pin connector (pin 14-15) on power supply.