IBM 5150 - Page 104

You may have a LED that has failed. If the diagnostic routines
run correctly
but the LED is not lit, check for a minimum of
1.5 V dc between P9-l and P9-2 on the Logic Printed Circuit
Board when
the spindle is turning.
•
DO YOU HAVE FUNCTIONING DIAGNOSTICS, AT LEAST
1.5 Vdc AT P9 AND A LED THAT DOES NOT LIGHT?
YES Replace the LED assembly. See Section 3,
"Removal/Replacement. "
NO
600-9