If the “power good” light is not on and if the power-supply fan is not running, check the power cord for continuity and proper installation.
If the power cord is not the problem, either the power supply is defective or another component is defective and is causing the power supply to shut off. To verify that the power supply is operating correctly, do the following:
1. Power-off the 3550 Expansion Unit and disconnect the 3550 Expansion Unit power cord.
2. Remove all power supply connectors (power supply connector P1, P2 and drive connector 1) from the system board of the 3550 Expansion Unit and SCSI device.
3. On power supply connector P2, short-circuit pin 4 to pin 6 and short-circuit pin 7 to 8.
4. Connect the 3550 Expansion Unit power cord.
5. Check the power supply voltages using the figures on the next page.
If any of the voltages are not correct, replace the power supply.