IBM 3270 Maintenance Manual page 225

1. Set the Power switch on the system unit (and
expansion unit, if attached) to Off.
2.
Reinstall the diskette-drive logic board and
connectors you disconnected earlier (see
Section 5, "Removal/Replacement and
Adjustments").
3.
Insert your Diagnostics diskette.
4.
Set the Power switch on the expansion unit
(if attached) and the system unit to On.
CONTINUE
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Maintenance Information