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|  TM 11-5820-509- 35
Item
Indication
Probable trouble
Procedure
4
No audio output (or low output) at
a.
Driver A1Q10 not adjusted
a.
Check audio output at A1J14
headset terminals.
properly or defective.
(normal 11 volts p-p); adjust
receiver gain control (para 3-22),
repair AM-3506/PRC-47, or
replace module.
b.
Audio output amplifier A1Q11-
b.
Repair AM-3506/PRC-47 (para
A1Q12 defective.
3-13a ) or replace module.
c.
Audio output circuit on main
c.
Check continuity from J2-24 to
chassis defective.
VOLUME control; from
VOLUME control to P2-L and
P3-L. Repair circuit if necessary.
Check VOLUME control for
continuity throughout its
rotation, check C20 and C24 for
shorts, and resistance of R24
and R25 (normal 15K ohms).
Replace any defective com-
ponent, repair the circuit as
necessary.
5
Excessive distortion on receive
a.
The -agc circuit of audio
a.
Check -agc level at A1J15
{due to front-end or if.
frequency amplifier A2 defective.
(normal 0 to -0.5 volts dc);
overloading).
adjust agc gain (para 3-23)
Repair AM-3506/PRC47 (para
b.
The -agc circuit on the main
b.
Check continuity from J2-20 to
chassis is defective.
L2-1, from L2-2 to J6-4; repair
as required. Measure resistance
of L2 (normal 1.2 ohms); replace
if defective.
c.
The +agc circuit of audio
c.
Check +agc level at A1J16
frequency amplifier A2 defective.
{normal +5 to +6 volts dc);
repair AM-3506/PRC-47 (para 3-
13a) or replace module.
d.
The +agc circuit on the main
d.
Check continuity from J2-16 to
chassis is defective.
J4-5; repair as necessary.
e.
The -agc circuit in signal data
e.
Repair CV-1377A/PRC-47 (para
translator A3, or the +agc
3-13c ) or AM-3506/PRC-47
circuit in audio frequency
amplifier A2 defective.
defective module.
malfunctions to a module within the transmitter circuits.
procedures in the order listed for isolation of
Item
Indication
Probable trouble
Procedure
Place the POWER-LIGHTS switch on the front panel of RT-671/PRC-47 to POWER OFF. Connect the test equipment for
transmitter tests (fig 3-3). Adjust the KILOCYCLES indicator to read 2000. Verify that the selector switch on the antenna
simulator is at the 2.0 MHz position. Resonate the power amplifier at the operating frequency using the OPR-TUNE switch
Caution:
Do not leave the OPR-TUNE switch in the TUNE position for more than a few seconds at a time. Damage to the power
amplifier plate circuit can result.
Connect the audio oscillator to A1J1 (fig. 3 4) and adjust its output level to 0.1 volt rms at 1.000 Hz.
1
No transmit audio, or low audio
a. Audio frequency amplifier A1
a. Check audio at A1J7 (normal
level, at balanced modulator
not adjusted properly or
0.25 volts rms): adjust
input (J3-3).
defective.
microphone amplifier gain
control A1R27 (para 3 25),
repair AM-3506/PRC-47 (para 3-
13a ) or replace defective
module.
b. Transmit audio circuit in main
chassis defective.
J2-22. from J2-C to J3-C and
J2-25. Check microphone circuit
from P2-E to P3-E and J2 2.
Repair as required. Check
capacitors C22 and C23 for
shorts: replace defective com-
ponents.
3-83
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