IBM 6151 Maintenance And Service Manual page 378

Step 8
1.
Set the system unit power switch to Off.
2. Connect the smaller power cable to the system board.
3. Disconnect the operator panel cable 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
Exchange the system board; then go to "Step 14" on
page 3-8800-14.
YES
Exchange the operator panel; then go to "Step 14" on
page 3-8800-14.
3-8800-8
Service Manual