IBM 5150 Hardware Maintenance Manual page 114

Reinstall the Logic Printed Circuit Board. Position the
System Unit Power switch to Off for five seconds, insert your
Advanced Diagnostic diskette, then power the System Unit
on. Test for an increase (approximately 0.2 Vdc) at TP-S on
the Logic Printed Circuit Board during the POST while the
LED is lit.
o
•
DOES THE VOLTAGE AT TP-5 INCREASE
(APPROXIMATELY 0.2 Vdc) WHEN THE "LED" IS LIT?
NO
Replace the Diskette Drive assembly. See Section 3,
"Removal/Replacement. "
YES
Replace Diskette Drive Adapter. See Section 3,
"Removal/Replacement. "
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