Checks and correctlve measures
Transceiver squelch control not ad-
Excessive noise in headset
during periods of no signal
Audio signals are distorted,
a. Transceiver defective ------------------
Replace transceiver (para 4-17).
or contain excessive hum.
b. Connect headset and microphone di-
b. Aircraft Cl61lD/AIC defective __
rectly to transceiver PHONE and
MIKE jacks and operate radio act.
If distortion or excessive hum is no
longer present, trouble is isolated to
C-1611D/AIC. Refer C-1611D/AIC
to higher category maintenance for
c. Audio cables defective, or shield
Request higher category maintenance
check of audio cabling.
not properly grounded.
Radio set operates on some
a. Replace control unit (para 4-16).
a. Control unit defective . . . . . . . . . .
frequencies but not on
b. Replace transceiver (para 4-17).
b. Transceiver defective ------------------------
a. Replace transceiver (para 417).
Reception and transmission
a. Transceiver defective ---------- - - - - - - - - -
b. Request higher category maintenance
b. Antenna or antenna rf intercon-
check of antenna and associated rf
necting cabling defective.
Replace control unit (para 4-16).
VOL control defective . ---------------
Operation of Control Unit
VOL control does not
change received audio sig-
Worn or damaged resilient mount(s)
Replace resilient mounts as necessary
Mounting does not operate
smoothIy or provide speci-
fied limits of travel to
protect transceiver from
shock and vibration.
Section IV. REMOVAL AND REPLACEMENT
4-14. Control Unit Panel Lamp
4-15. Control Unit Control Knobs
a. The MHz timing control knob and the OFF-
PWR switch are on the same mounting shaft, and
Be sure that the 27.5-volt dc circuit
the VOL. control knob and the kHz tuning c o n -
breaker that supplies power to the radio
trol knob are on the same mounting shaft ( f i g .
set is deenergized before performing the
3 - 1 ) ; however, each of the knobs is a separate,
procedures given below.
i n d e p e n d e n t section. When replacing the r e a r
sections, it is necessary to first remove the associ-
ated tuning control knob.
Check to see that the washer and rubber ring re-
b. Perfor-m the procedures given below when
m a i n in place on the lampholder during removal
removing and replacing the control knobs.
When replacing a rear section knob,
check to see that it does not drag or
b . Remove the defective l a m p from holder
bind against the front panel of the con-
w i t h a sharp-bladed instrument to separate the
trol unit after the setscrews that hold it
base of the lamp from the holder,
in place have been tightened. Also check
c. Insert a new lamp firmly into the holder.
to see that the front knob does not bind
or drag against the rear knob after the
d. Screw the lampholder
into the front
setscrews have been tightened.
panel of the control unit.