IBM 3274 51C Maintenance Information page 269

F.3.2 Head/Carriage Assemb/y
Warning: The head/carriage assembly is adjusted and tested
at the factory. Do not attempt to adjust or repair any part
of this assembly.
Do not attempt to clean the head/carriage assembly. If the
assembly is not clean, exchange it.
F~3.2.1
Head/Carriage Service Check (Figures F-22, F-23),
Warning: The head/carriage service check must be per-
formed with the diskette drive installed (or with the disk-
ette drive in the same position as when installed) or the
adjustment might not be accurate.
1. Power down.
I
DANGER
Voltage is still present at the socket when the power
cable is disconnected.
2. Disconnect the ac drive motor power cable
0 .
3. Remove the head cable guide
O.
4. Turn the stepper motor pulley by hand to track 40,
and insert a timing pin
e.
(Ensure that the pin goes
into the casting.)
5. Power up.
6. To disable the stepper motor, install a jumperO
from TPB02 (ground) to TH05 (-'disable stepper
motor').
7. To locate the stepper motor at track 40, install a
jumper
G
between TPA07 (ground) and TPA04
(MC-O).
8. Put the timing pin
G
through the stepper motor
pulley into the timing hole in the casting. Does the
timing pin
pa~~
freely through
th~
hole?
y
N
Remove the timing pin
e .
Remove the jumpers
0
and
Q) .
Power down.
Go to the Head/Carriage Adjustment
(paragraph F .3.2.2), step 3.
9. Remove the timing pin
e .
F-26
..
~
..
10. To remove the stepper motor to track 39, remove the
jumper connected to TPA04 and· install the jumper end
on TPAOl (MC-3).
11. Verify that this is track 39 by visually checking for no
gap
CD
between the timing pointer
G
and the tim-
ing block
CD .
12. To move the stepper motor from track 39 back to
track 40, remove the jumper connected to TPAOl
and install the jumper end on TPA04 (MC-O).
13. Verify that this is track 40 by visually checking that
the timing hole in the pulley lines up with the timing
hole in the casting. (Use the dental mirror to verify;
do not use a timing pin.)
14. Insert the thickness gauges from the end of the timing
pointer
G
and timing block
CD
to verify the indi- .
cated gap
G :
- 0.483 mm (0.019 inch). Go.
- 0.533 mm (0.021 inch). No go.
Note: Because of the torque characteristics of the
stepper motor, this step can be performed only once.
If it is necessary to perform this step again, go back
to step 10 of this service check.
15. If the adjustment is not correct, go to step 12 of
paragraph F .3.2.2.
16. Remove the jumpers
0
and
G .
17. Reinstall the head cable guide
G.
(Ensure that the
read/write head can move freely.)
18. Was the head/carriage assembly exchanged?
y
N
I
Power down.
Reconnect the ac drive motor power cable.
Power up.
End of procedure.
19. Go to the Head Gap Service Check (paragraph F .3.3.2).