IBM RT PC 10 Hardware Maintenance And Service page 142

Step 2
1. Set the power switch on the system unit to Off.
2. Exchange the fixed-disk and diskette adapter.
3. Be sure the power has been off 30 seconds, then set the power switch
on the system unit to On.
4. Wait two minutes, then answer the following question.
IS "23" DISPLAYED IN THE TWO-DIGIT DISPLAY?
NO Set the power switch on the system unit to Off, then go to "Step
4" on page 3-99.
YES Set the power switch on the system unit to Off.
1. Exchange the system board.
2. Go to "Step 4" on page 3-99.
Problem Isolation Charts 3-97