IBM 5280 Maintenance Information Manual page 130

Page of SY31-oa02-0
As updated 5 June 1981
By TN L SN20-9529
Head/Carriage Assembly
337
HEAD/CARRIAGE SERVICE CHECK
CAUTION
The head/carriage service check must be performed with
the diskette drive installed (or in the same position as when
installed) or the service checks might not be accurate.
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1. Go to 361 , step 1.
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~~~~t~~
discnaige voltage might be present at the socket
when the AC drive motor power cable is disconnected.
2.
Disconnect the AC drive motor power cable
II.
3.
Remove the cable guide
m.
4. Turn the stepper motor pulley IJby hand to track
40 and insert a timing pin
II.
(Ensure that the
timing pin goes into the casting
II.)
CAUTION
The PTX, LED, or diskette drive control card might be
damaged if you install jumpers on the wrong test pins.
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5. Install a jumper from
fJ
(ground) to g(-disable
stepper motor).
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6. . I nstall a jumper from
D
(ground) to
II
(MC-O) to
electrically detent the stepper motor.
, 7.
8.
9.
Power on.
Remove and reinsert the timing pin.
If the timing pin passes freely through the stepper
motor pulley into the timing hole in the casting, go
to step 13. If the timing pin does not pass freely
through the stepper motor pulley into the timing hole
in the casting, proceed with step 10.
10. Remove the timing pin.
11. Power off.
10 Head/Carriage Assembly
·12. Go to 339 step 2.
13. Remove the timing pin.
14. Remove the jumper end from
II
(MC-O) and install
it on D(MC-3). This moves the stepper motor
pulley to track 39.
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15. Verify that the stepper motor pulley is at track 39 by
visually checking for no gap between the timing
pointer and the timing block
1m.
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16. Remove the jumper end from
II
(MC-3) and install
it on
II
(MC-O). This moves the stepper motor
pulley to track 40.
f
17. 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 the timing pin.
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18. Check the gap between the timing pointer and the
timing blockim as follows:
a. Insert thickness gauges totaling 0.483 millimeter
(0.019 inch) between the timing block and the
timing pointer and visually check that the
head/carriage assembly does not move.
b. Insert thickness gauges totaling 0.533 millimeter
(0.021 inch) between the timing block and the
timing pointer and visually check that the
head/carriage assembly moves slightly.
Note: Because of the torque characteristics of the stepper
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motor, step 18 can be performed only once. If it is
necessary to perform this step again, go back to step 14
337
of this service check.
19. If the conditions in step 18 are not
~orrect,
go to
339, step 8. If the conditions are correct, proceed
with step 20.
20. Power off.