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Continuity and Short Circuit Tests for Cable Assembly, Special Purpose, Electrical CX-4655/GRC
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TM-11-5820-498-35 Radio Sets AN/VRC-53 AN/VRC-64 AN/GRC-125 and AN/GRC-160 and Amplifier Power Supply GROUPS 0A-3633/GRC and 3633A/GRC Manual
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Figure 3-6. AM-2060(*)/GRC, front and rear panel connectors J2, J3, and J4, voltage and resistance indications.


TM 11-5820-496-35
(3) Transmit dummy load assembly (para
3-9. AM-2060(*)/GRC, Isolating Troubles in
Audio Amplifiers Q1 and Q2
b. Test Setup.
When trouble has been localized to audio ampli-
(1) Remove the access plate (fig. 3-10)
fiers Q1 and Q2, use the following procedures
from the top of the AM­2060(*)/GRC to gain ac-
to isolate the defective part in the circuit.
a. The following equipment is required:
cess to the test points El through E22 on the
plug-in assembly (fig. 3-9).
(1) A 25.5-volt dc power source (or 25.2-volt
(2) Connect the transmit dummy load as-
output of Power Supply PP­2953(*)/U).
sembly to SET POWER connector J2 (fig. 3­8).
(2) Generator, Signal AN/URM-127.
(3) Voltmeter, Electronic ME-30(*)/U.
(3) Connect the dc power source (a(1)
(4) Receive dummy load assembly (para
above) to pins A (chassis ground and J of
POWER INPUT connector J3 (fig. 3-8).
b. Remove the access plate (fig, 3­10) from the
(4) Set the PWR switch to ON.
top of the AM­2060(*)/GRC to gain access to the
c. Output Voltage Adjustments, R1O.
test points El through E22 on the plug-in assem-
(1) Perform the test setup given in b above.
bly (fig. 3-11 and 3-15).
(2) Connect the ME-26(*)/U, arranged as a
c. Connect the receive dummy load assembly to
dc voltmeter, between pins E (positive) and A
SET POWER connector J2 (fig. 3-7).
(chassis ground) (14.5-ohm load resistor) of
d. Connect the dc power source (a(1) above) to
SET POWER connector J2 (fig. 3­8).
pins A (chassis ground) and J of POWER INPUT
(3) Loosen the locknut holding the adjust-
connector J3 (fig. 3­7).
ment screw of R10 (fig. 3­11).
e. Set the PWR and SPKR switches to ON.
NOTE
f. Apply a 1-kHz, 1-volt signal from the
If the locknut cannot be easily loosened, use
AN/URM-127 with its adapter UG­514/U to pins
a drop of penetrating oil on the threads and
A (chassis ground) and B of SET POWER
allow it to penetrate before trying to loosen
connector J2 (fig. 3-7).
the locknut.
g. When the ME­30(*)/U is connected between
(4) Adjust R10 adjustment screw for an in-
pins E1 and E14 of the plug-in-assembly (fig.3-9),
dication of +13 volts on the ME-26(*)/U. Fin-
it should indicate 4.5 ± 0.10 volts ac. If the
gertighten the locknut holding the control.
ME-30(*)/U indication is not approximately 4.5
d. Isolating Troubles in Voltage Regulator Cir-
volts ac, make voltage and resistance measure
cuit Q3 and Q4.
ments of the audio amplifier circuit and also the
(1) Perform the test setup and adjustment
voltage regulator circuit.
procedures given in b and c above before proceed-
(1) To make the voltage measurements, leave
ing.
the dc power connected to connector J3 (d above)
(2) Measure the voltage drop across refer-
and make the voltage measurements at the pins of
ence diode CR1 by placing the ME-26(*)/U nega-
the plug-in assembly (fig. 3­9).
tive lead on test point E1 and the positive test
(2) TO make the resistance measurements,
lead on test point E6 (fig. 3-9). The ME-26(*)/U
remove the dc power from connector J3, and make
should indicate approximately 6.8 volts dc.
the resistance measurements at the pins of the
(3) Measure the voltage drop across ref-
plug-in assembly.
erence diode CR2 by placing the ME­26(*)/U
(3) Refer to paragraph 3-11 for dc resist-
negative lead on test point E3 and the positive
ance of transformers and coils involved in the
test lead on test point E4. The ME­26(*)/U
circuits.
should indicate approximately 6.8 volts dc.
(4) If the voltage indication obtained across
3-10. AM-2060(*)/GRC, Adjustment of R10,
CR1 and CR2 is still not within limits, make volt-
and Isolating Troubles in Voltage Regu-
age and resistance measurements of the voltage
lator Circuits Q3 and Q4
regulator circuits to determine the defective part.
When trouble has been localized to voltage regula-
tors Q3 and Q4, use the following procedures to
3-11. Dc Resistance of Transformers and Coils
isolate the defective part in the circuit.
The dc resistance of the transformer windings
a. Equipment Required.
and the relay coil on the plug-in assembly of
(1) A 25.5-volt dc power source (or 25.2-
the AM-2060(*)/GRC are listed in the following
volt output of Power Supply PP-2953(*)/U).
chart.
(2) Multimeter ME-26(*)/U.
3-9


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