IBM RT PC 10 Hardware Maintenance And Service page 119

Step 7
3-74 Service Manual
1. Set the power switch on the system unit to Off.
2. Connect the power connector to the cooling fan.
3. Disconnect the smaller power cable connector from the system board.
4. Be sure the power has been off 30 seconds, then set the power switch
on the system unit to On.
5. Wait 15 seconds, then answer the following question.
IS THE COOLING FAN OPERATING?
NO Check the external power cable for damage, if none, exchange the
power supply. This completes the repair.
YES
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