IBM 3270 Maintenance Manual page 412

1. Set the Power switch on the system unit (and
expansion unit, if attached) to Off.
2. Remove the IBM Math Coprocessor from the
system unit. See Section 5,
"Removal/Replacement and Adjustments."
3. Set the Power switch on the system unit (and
expansion unit, if attached) to On.
DID THE FAILURE SYMPTOM REMAIN?
NO
Replace the IBM Math Coprocessor and
the 8088 Processor. See Section 5,
"Removal/Replacement and Adj ustmen ts."
YES
October 1984 3-9999-7