Data Head; Leadscrew Wheel - IBM System/34 Maintenance Manual

23-220
DATA HEAD
To adjust the data head, you must obtain three
conditions at the same time:
• The correct gap from the data head to the 33FD
alignment tool
• The correct position between the stepper motor
wheel and the leadscrew wheel
• The correct space between the stepper motor and
leadscrew wheels
Note: This procedure aligns the data head at track 00.
Adjustment
Note: Run the head alignment exerciser before
performing this adjustment. If the head alignment is
good, go to the Diskette Quality Service Check (see
paragraph 23-310). If the head alignment is bad,
continue with this adjustment.
1. Set Power to 0 (operator panel).
2. Remove the covers (see paragraph 23-130).
3. Turn the stepper motor wheel until the head
carriage is against the lower stop
O.
4.
5.
6.
18
Loosen the mounting screw and move the
phototransistor assembly
0
to the left.
Note: If the phototransistor assembly is not
moved, the head adjustment can be made wrong.
Loosen the clamping screws on the lower limit
stop
0
and leadscrew wheel
e.
With the stepper motor wheel and leadscrew
wheel in position as in view
e,
insert a 0.51 mm
(0.020 inch) thickness gauge between the wheels
• in view
e.
Tighten screw
e
a small amount.
Note: The purpose of this step is to let the
stepper motor wheel pins go into the leadscrew
wheel the maximum distance with no binds.
7.
8.
9.
Locate the white spot label or the groove on the
outer edge of the hub. If the hub has both, always
use the white spot. Turn the hub to put this mark
180 degrees away from the data head.
Note: This ensures that if the hub is eccentric, it is
located in the same spot and. that all head
adjustments use the same reference point.
CAUTION
Do not let the 33FD alignment tool touch the shiny
surface of the head.
Install the 33FD alignment tool on the hub
G.
Clamp it into place with the thumbscrew and· turn
the CE tool so it touches surface
G).
Turn the leadscrew by holding the upper limit stop
8;
adjust for gap
G.
This gap is a number on
the front of the head assembly
G.
This number
represents thousandths. Example: 3 is the same
as 0.076 mm (0.003 inch). Adjust for a very light
drag on a 0.003 inch gauge. A 0.002 inch gauge
must be free.
Note: Remove the thickness gauge from the pack
to make this adjustment.
10. Ensure the stepper motor wheel and leadscrew
wheel remain in position
e;
then tighten the
leadscrew wheel clamping screw
e.
The top of
t~e
clamping collar should be approximately even
with the top of the metal clamping surface of the
leadscrew wheel
O.
23-220
CAUTION
If the clamping collar is not tightened, machine
operation causes the head to go out of
adjustment. However, do not over tighten the
clamping screw, because it can damage the screw
or cause the screw to break.
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