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3.2.22 Phototransistor
Service Check
1.
2.
3.
Turn power off at the operator control
panel.
Remove the 33FD from the machine and
disconnect the drive motor plug (3.2.5).
Attach the positive probe of VOM (15 Vdc
scale) to the +5 Vdc test point and the
negative probe to the phototransistor
current test point on the file control card
located on the 33FD (facing page).
4.
Insert a diskette, close the cover, and
turn the power on.
5.
Note:
Always perform the following pro-
cedure with the diskette loaded; otherwise,
surrounding light causes an improper read-
ing on the VOM.
With head unloaded, rotate the hub until
the index hole switches the phototransistor
on or off. (When the phototransistor is
aligned with the index hole, the VOM reads
approximately +5.0 Vdc; when it is not
aligned, the VOM reads approximately 0.0
Vdc).
The shift will be from approximately +5.0
Vdc to approximately 0.0 Vdc. However, a
minimum shift of 0.5 Vdc (from +5.0 Vdc
to +4.5 Vdc) will switch the circuit.
6.
Connect the drive motor plug.
7.
E
u
---
>
N
If scope is available, connect probe to
'+Index' (see card probe points on
facing page). Check for an index pulse
width of 1.7 to 8.0 ms. Check for
approximately 160'ms between index
pulses.
Ground
5001ls/cm
7.
Turn the power off, check that cables are
connected; then install the 33FD in the
machine.
Adjustment
1.
2.
Turn power off at the operator control
panel.
Remove the 33FD from the machine
(3.2.5).
3.
Access to track O.
4.
5.
6.
7.
Remove the covers (3.2.8).
Loosen the mounting screw
Ii
,and
move the phototransistor to the left.
Install CE tool
m
by screwing the thumb-
screw into the drive hub
D .
Rotate tool
until it contacts surface
m .
Adjust phototransistor so that raised edge
is in contact with the CE tool
E1 .
8.
Tighten the mounting screw.
9.
Remove CE tool.
10.
Replace covers (3.2.8).
11.
Install the 33FD in the machine.
Removal
1.
2.
Turn power off at the operator control
panel.
Remove the 33FD from the machine
(3.2.5).
3.
Access to track O.
4.
Remove covers, if necessary (3.2.8).
5.
Remove mounting screw
I) .
6.
Remove leads.
3-22
Replacement
1.
2.
3.
Replace leads. (Yellow wire goes to ter-
minal marked Y.)
Replace mounting screw, but do not tighten.
Complete replacement by doing adjustment
starting at step 4.
Install CE tool by
screwing thumbscrew
into drive hub.
Rotate CE tool
so it contacts
this surface.
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