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  TM 11-6625-524-14-2
top, and sides. Set the power supply
(1) Disconnect the wire from 3A2TP12 and
voltage at - 14.5 volts before making any
connect it to 3A2TP11.
gain measurements.
(2) Disconnect the jumper from 3A2TP8 and
connect it to 3A2TP10.
a. Checking Waveshapes of 3A2 Am-
(3) Set the LINE switch at ON,
plifier. Perform the following steps to check the
(4) The voltage from 3A2TP11 to ground
amplifier.
shall measure 1.5 volts DC ± 10 percent. If not,
(1) Set the range selector switch at 0.001
adjust 3A2R53.
range.
(2) With no input, adjust the SET REF
control until the meter pointer is at the SET REF
mark. The waveshape from 3A2TP5 to ground is
The dc resistance of transformers is shown below.
shown in figure 5-10.
When using the data, observe the following:
(3) Connect the H-P 606A signal generator
a. Before making resistance measurements of
to the rf probe.
the windings, determine that the faulty operation
(4) Set the signal generator output for 1 mv
is due to a defective transformer. To do this,
at 200 KHz. The waveshape is shown in figure 5-
follow the troubleshooting procedure in
10. Any drastic deviation indicates a faulty
amplifier.
b. Because of the rather broad winding
b. Checking Modulator and Narrow Band
tolerances during manufacture, resistances may
Preamplifier. Perform the following steps to
vary from one transformer to another; the values
check the modulator and narrow band pream-
shown are typical average values.
plifier:
c. The normal resistance of replacement
(1) Disconnect the jumper between 3A2TP8
transformers may differ greatly from the values
and TP9.
given below.
(2) With no input, the waveshape at 3A2TP8
is shown in figure 5-10.
(3) Connect the H-P 606A signal generator
Transformer 3A1T1
Transformers 3A2T1 and T2
to the rf probe.
Terminals
Terminals
Ohms
Ohms
(4) Set the signal generator output for 1 mv
at 200 KHz. The waveshape is shown in figure 5-
1-3
1.3
2-3
2-3
10. If the peak-to-peak output is low, adjust
4-6
3A2R11.
4-6
c. Checking Output Amplifier. Perform the
5-6
following steps to check the output amplifier.
Section Ill. MAINTENANCE
6-7. Removal of Pc Board
6-6. Alignment
Perform the following steps to remove a printed
Perform the following steps to align the volt-
circuit (pc) board.
meter.
a. Remove the six screws and washers located
a. Connect the negative lead of the vtvm to
3A1TP1 and the positive lead to 3A1TP2.
at lower sides of the top cover and lift the cover up
b. clear the voltmeter.
b. Adjust 3A1R13 (VOLTS ADJUST) for 14.5
b. Remove the five screws and washers on the
volts indication on the vtvm.
3A1 and 3A2 boards and lay the boards flat.
c. With the power off, adjust the mechanical
c. Unsolder and tag all wires connected to the
zero adjust screw to bring the meter pointer to the
pc board and remove the board.
SET REF mark.
d. On the 3A3 pc board, perform the following
d. Terminate the rf probe in 50 ohms and
steps:
attach the probe to the voltmeter.
e. Set the LINE switch at ON.
(1) Remove six screws and washers holding
the rear plate.
f. Turn the SET REF control until the meter
pointer is at the SET REF mark.
(2) Remove six hexagon headscrews and
washers holding the board and lay the board flat.
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