TM 11-6625-486-14&P
to the frequency meter side panel. Adjust the 100-MHz
(250 kHz). A zero beat should be obtained as the
converter GAIN control for a satisfactory counter
CORRECTOR control is tuned.
readout. I f the readout is erratic, decrease the gain.
NOTE
(5) Note the readout display of the counter.
The
frequency
range
of
the
The counter should indicate either the 250-kHz
CORRECTOR at 250 kHz is slightly
fundamental frequency 25 hertz or the 500-kHz
greater than 25 Hz, and at 125 kHz
second harmonic frequency 50 hertz. If incorrect,
slightly greater than 12.5 Hz which
adjust C114 for correction.
is sufficient to obtain the original
0.01-percent accuracy of the vfo. If a
(6) As a final readout accuracy check, tune
zero beat cannot be obtained with
the frequency meter to the 125-kHz checkpoint and note
the CORRECTOR control on a crystal
the counter readout. The frequency should be either
checkpoint, the filmstrip alignment
125 kHz 12.5 Hz or 250 kHz 25 Hz.
b. Range B.
recalibrated.
(1) The counter can be used to read out the
(4) Turn the RANGE SW to B and tune the
frequency of this range is fundamentals without using
frequency meter to the lowest checkpoint (2,500 kHz,
harmonics. Set up the counter as instructed in a (1)
2.5 MHz) on the filmstrip. Leave the FUNCTION SW
above.
set to CHK.
(2) Turn the frequency meter RANGE SW to
(5) Adjust the CORRECTOR control for a
B and set the CORRECTOR control to the midpoint.
zero beat as heard in the headset. Tune the frequency
Tune the frequency meter to the 5,000-kHz checkpoint.
meter to the last checkpoint (5,000 kHz). A zero beat
should be obtained as the CORRECTOR control is
(3) Connect the counter SIGNAL INPUT to
turned.
the collector of Q301. On the counter, adjust the
converter GAIN control for a satisfactory readout. If the
6-28. Adjustment of High Frequency Vfo
counter readout is erratic, decrease the converter gain.
This vfo covers a fundamental frequency range of 65 to
130 MHz. A minimum of 27 crystal checkpoints, spaced
(4) Note the readout frequency of the
at 2.5-MHz intervals from 65 to 130 MHz on the
counter. The counter should indicate 5,000 kHz 500
filmstrip, enables this range to be checked to a high
Hz. I f incorrect, adjust C112 for correction.
degree of accuracy. Provided the frequency range of
(5) Tune the frequency meter to the 2,500
the CORRECTOR is .sufficient to correct this vfo on any
kHz checkpoint and note the counter readout frequency.
of the above checkpoints, the vfo accuracy between
The frequency should be 2,500 kHz 250 Hz.
checkpoints should equal the original 0.01-percent
accuracy. If a zero beat cannot be obtained on some of
c. Checking Low Frequency Vfo Against Crystal
the crystal checkpoints, and it has been definitely
Check points.
established that the crystal oscillator is not at fault, the
(1) Remove
the
electrical
connection
high frequency vfo will need recalibration.
To
between the counter and the meter. Turn off the
recalibrate the high frequency vfo, switch the RANGE
counter.
SW to C. Tune the frequency meter to the highest
(2) Turn the frequency meter FUNCTION SW
crystal checkpoint. If unable to obtain a zero beat,
to CHK and the RANGE SW to A. Plug the headset into
adjust C5. Check the tracking of the oscillator at every
a PHONES jack.
checkpoint from the highest to the lowest on range C.
(3) Tune the frequency meter to the lowest
Vary C5 and spread or compress L1 to obtain proper
checkpoint (125 kHz) on the filmstrip. A zero beat
tracking. Do not adjust L1 unless it is absolutely
should be obtained as the CORRECTOR control is
necessary.
turned. Tune the frequency meter to the last checkpoint
Section V. GENERAL SUPPORT TESTING PROCEDURES
6-29. General
repaired equipment must meet before it is returned to
a. These testing procedures have been prepared
the using organization.
for use by general support maintenance shops to
determine the acceptability of repaired equipment.
b. Comply with the instructions preceding each
These procedures set forth specific requirements that
table before proceeding to the table itself. Perform each
step in sequence. For each step
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