Power Supply - IBM PC 300 Maintenance Service Manual

Power Supply

001 - START
Power off the system unit.
Check the power cord for continuity. Replace if necessary.
Check for the correct line voltage from the power outlet, and verify that the voltage selector switch is set to the correct
voltage.
Power on the system unit.
002 - DOES THE POWER SUPPLY FAN RUN? (YES, GO TO STEP 003. NO, GO TO STEP 004)
003 - DOES THE SYSTEM FAIL TO SHUT OFF WHEN THE ON/OFF SWITCH IS PRESSED? (YES, READ AHEAD. NO,
GO TO STEP 005)
You might have a damaged on/off switch cable assembly.
Disconnect the on/off switch cable assembly connector from the power supply connector and take an ohm reading.
Go to step 007.
004 -
Disconnect the power cord from the back of the system unit.
Disconnect all power and switch cable connectors from the system board and the power supply.
Disconnect the power connectors to all drives.
Connect the power connector to system board as a power load for driving up power supply.
Reconnect the power cord.
005 - DOES THE POWER SUPPLY FAN RUN? (YES, READ AHEAD. NO, GO TO STEP 009)
With the system powered on and the power supply fan running, check the voltages of the power supply connectors for
the system board and all drive connectors, as shown in the following figures.
11
1
Power Supply Connectors (Bottom View)
Hard Drive or CD-ROM End of Power Cable
3.5-In. Diskette Drive End of Power Cable
20
10
77