IBM 5150 Hardware Maintenance Manual page 121

Remove the Diskette Drive Belt and turn the spindle to be
sure that it turns freely and without binds.
®
Bottom View
DOES THE SPINDLE TURN FREELY?
NO
Replace the Spindle assembly. See Section 3,
"Removal/Replacement. "
YES
Replace the Diskette Drive Motor. See Section 3,
"Removal/Replacement. "
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