Head/Carriage Adjustment - IBM 5280 Maintenance Information Manual

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.
1.
2.
3.
4.
5.
6.
7.
8.
Power off.
DANGER
Capacitor discharge voltage might be present at the
socket when the AC drive motor power cable is
disconnected.
Disconnect the AC drive motor power cable
m.
Remove the cable guide
lID.
Measure and record the gap
II
between the stepper
motor pulley and the casting. The gap is _ _ _ _ _
Loosen the clamp screw
II
so the stepper motor
shaft can turn inside the pulley.
Turn the stepper motor pulley Dby hand to track
40 and insert the timing pin
IJ.
Power on.
Install a jumper from
fI
(ground) to
II
(-disable
stepper motor).
9. Install a jumper from
0
(ground) to
II
(MC-O).
10. Set the gap
0
to the same size as the gap recorded in
step 4 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
339
11. Remove the timing pin.
12. Loosen the two screws
Em
that hold the bracket to
the carriage.
13. Remove the jumper end from
II ;
and momentarily
touch it to
a .
14. Reinstall the jumper end on
II.
Note: Steps 13 and 14 set up the required torque condi-
tion of the stepper motor for the following steps.
15. 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.
16. Insert thickness gauges
m
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
1m
to the casting
with the retaining clipiE] provided (part 4240632).
The clip is attached to the diskette guide. (For
location, see 330
1m.)
17. Slide the head/carriage assembly against the thickness
gauge so it just touches but is not forced against the
thickness gauge. I nsert 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.)
18. Tighten the two screws that hold the bracket to the
carriage.
19. Remove the retaining clip and the carriage pressure
spring.
20. Go to 337, step 14.