IBM 3270 Maintenance Manual page 230

1. Use the Drive Motor Preliminary Speed
Adjustment to ensure the diskette drive speed
is correct (see Section 5,
"Removal/Replacement and Adjustments").
Note: Fluorescent lighting is needed on this
test to see the strobe effect.
2. Go to page 3-600-6, and perform steps 1
through 8, to do the diagnostic tests on a
formatted diskette. Then return to this page.
Type 1
Type 2
DO YOU STILL HAVE AN ERROR CODE?
NO
Do the diagnostic tests to verify you have
fixed the problem.
YES
October 1984 3-600-31