IBM 5280 Maintenance Information Manual page 103

Page of SY31-0602-0
As updated December 5, 1980
By TN L SN20-9590
339
HEAD/CARRIAGE ADJUSTMENT
CAUTION
The head/carriage assembly adjustment must be performed
with the diskette drive installed (or in the same position as
when installed) or the adjustment might not be accurate.
Note: This procedure should not be performed unless para-
graphs 363 and 337 have been completed or you were di-
rected to this procedure from another manual.
1 . Power off.
DANGER
Capacito~ discharge voltage might be present at the
socket when the AC drive motor power cable is
disconnected.
2. Disconnect the AC drive motor power cable
m .
3. Remove the cable guide
1m .
4.
Go to 341 step 12.
5. Measure and record the gapllbetween the stepper
motor puJley and the casting. The gap is
6. Loosen the clamp screwllso the stepper motor
shaft can turn inside the pulley.
7. Turn the stepper motor pulleyl!lby'hand to track
40 and insert the timing pinIJ.
8. Power on.
9. Install a jumper from fJ(ground) to
II
(-disable
stepper motor).
10. Install a jumper from
D
(ground) to
II
(MC-O).
11. Set the gapEJto the same size as the gap recorded in
step 5 and tighten the clamp screw. (Ensure that the
timing pin passes freely through the stepper motor
pulley into the timing hole in the casting.)
12 Head/Carriage Assembly
12. Remove the timing pin.
13. Loosen the two screws
1m
that hold the bracket to
the carriage.
14. Remove the jumper end from
II ;
and momentarily
touch it to
II .
15. Reinstall the jumper end on
I).
Note: Steps 13 and 14 set up the required torque condi-
tion of the steppe'r motor for the following steps.
16. Verify that the stepper motor pulley is at track 40 by
visually checking that the timing hole in the pulley is
aligned with the timing hole in the casting. Use a
dental mirror to check. Do not insert a timing pin.
17. I nsert thickness gauges
If)
totaling 0.508 millimeters
(0.020 inch) between the timing pointer on the
carriage and the track 40 adjustment surface on the
casting. Clamp the thickness gauge
If)
to the casting
with the retaining clipliJprovided (part 4240632).
The clip is attached to the diskette guide. (For
location, see 330
1m.)
18. Slide the head/carriage assembly against the thickness
gauge so it just touches but is not forced against the
thickness gauge. Insert the carriage pressure spring
iD(part 4240631) between the casting and the
carriage to hold the carriage against the thickness
gauge. The carriage pressure spring is attached to the
diskette guide. (For location, see 330
1m.)
19. Tighten the two screws that hold the bracket to the
carriage.
20.
Remoye the retaining clip and the carriage pressure
spring.
I
21. Go to 337 step 15.
339