TM 11-6625-486-14&P
2,500-kHz checkpoint is centered under the hairline;
insertion in the bottom spool holding slot. Thread this
then, tighten the two Allen screws.
end of the film over the guide spool, under the filmstrip
viewer bezel, and round the sprocket wheel to the
(8) Tune the meter to several other
bottom spool.
checkpoints on range B and note if the zero beat can be
(7) Pull up all slack in the filmstrip and insert
obtained on the checkpoint. If the filmstrip is properly
the end of the film in the spool holding slot. Secure the
centered for the 2,500-kHz checkpoint, all other
film to the spool with paper tape.
checkpoints should be correct.
(8) Rotate the bottom film spool and wind
(9) Secure the filmstrip mask operating lever
approximately 8 turns of film; then, remove the two
to mask with the associated hardware.
machine screws that were inserted ((3) above).
(10) Install left side panel and replace the
attaching screws. Replace front panel DIAL LOCK
c. Replacing Filmstrip Mechanism.
knob.
(1) Place the filmstrip mechanism on the
frequency meter chassis and mate the shaft coupling pin
with the associated TUNING control shaft coupling unit.
If transistor Q1, in the high frequency vfo, has been
NOTE
replaced, readjust potentiometer R4 (fig. FO-2 (2) or
To accomplish the above, rotate the
FO-3 (2) ) as follows:
film mechanism shaft slightly, if
a. On the meter front panel, turn the FUNCTION
necessary. Do not turn the shaft any
SW to OPER and the RANGE SW to range C.
more than necessary. Also, be sure
b. Set the vtvm FUNCTION to AC and the RANGE
that the TUNING control is still at its
to IV. Refer to figure FO-2 (2) or FO-3 (2).
upper stop position.
(2) Secure the filmstrip mechanism to the
c. Connect the rf probe ground clip to the vfo
chassis with the four screws that were removed (a (6)
compartment side panel and touch the probe tip to the
above). Do not replace the left-side panel at this time.
collector of Q2. Note the rf signal level at this point.
(3) Insert the dial lamp cable through the hole
d. While holding the ac probe on Q2, rotate the
in the chassis and solder the wires to terminals 2, 3, and
TUNING control in any direction until the ac signal level
4 on the modulator circuit board.
reaches the greatest amplitude indicated on the vtvm.
(4) Turn the RANGE SW to B and the
This frequency setting is the point of maximum oscillator
FUNCTION SW to CHK. Manually push the film mask
activity. Remove the ac probe connection but do not
to range B. Plug the headset into one of the PHONES
touch the TUNING control knob.
jack.
e. Set the vtvm FUNCTION to DC- and the
NOTE
RANGE to 10V. Connect the common clip to the
Do not connect the mask operating level.
chassis and the dc test prod to the collector of Q1.
(5) Rotate the TUNING control until the
2,500-kHz checkpoint is under the hairline indicator If
f. Turn potentiometer R4 (fig. FO-2 (2) or FO-3
the beat note is heard, adjust the CORRECTOR control
(2) until the vtvm indicates 3.15 volts.
The
for zero beat. If the beat note cannot be heard, refer to
potentiometer is then set correctly and should not be
the procedure given in (6) below.
touched unless Q1 is replaced again.
(6) Slowly tune the frequency meter in the
immediate vicinity of the checkpoint until the beat note
is heard. If the beat note occurs on a calibration mark
The crystal oscillator in the frequency meter is quite
displaced from the 2,500-kHz checkpoint, adjust the
stable and normally requires adjustment only at very
CORRECTOR control for a zero beat and leave the
infrequent intervals, or unless a part has been replaced
TUNING control set at this point.
that may effect the frequency.
If adjustment is
(7) Look down on the film mechanism shaft
necessary, use the alignment setup given in figure 6-14
and locate the insulated coupling unit between the film
and the procedure outlined below:
mechanism shaft and the TUNING control shaft (fig. 6-
a. Plug Frequency Meter Subassembly MX1637/U
(100-MHz converter) into the counter front panel. In the
left side of the insulated coupling unit (nearest to the
converter, only the video
film mechanism). The film mechanism shaft can now
be turned while the TUNING control shaft remains
stationary. Turn the film mechanism shaft until the
6-26
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