J7 Connector Pinout Models 25, 25SX and 25-286(Pin 1 to rear of system)
P3 / P4 Connector Pinout Model 30 and 30-286(Pin 1 to rear of system)
The manually-switchable power supply must be switched to either the 100-125 Vac or the 200-240 Vac range before the power cord is plugged into an outlet. The ac input is converted to dc outputs that supply the system with the proper operating voltages.
When the system is powered-off for five seconds or more and then powered-on, the power supply generates a 'power good' signal that resets system logic. The presence of the 'power good' signal indicates that the power supply is operating properly and that the minimum under-voltage sense levels have been established. This means that all system-board power requirements have been met.
Once the minimum under-voltage sense levels are established and the 'power good' signal has risen to its active level, all system board power requirements have been met and the power-on self-test begins.
Power Good should read +3.5 to +5 V when system is operating correctly. If it is not, remove all adapters, cables, and extra memory then try again. If power good is now valid, a device was causing a short. Install adapters one at a time and retest. The bad device will prevent power good from coming up.