TM 11-5826-225-35
o n d RF amplifier Q3 (figs. 2-8
a n d 2-10 or 2-10.1).
(9) Set control unit and signal generator
. Set signal generator for an un-
controls for using RF test signals on
modulated 200-kc output signal at a
the 400- to 850-kc and 850- to 1750-kc
level of 50 microvolt.
ranges. For each test signal, set con-
trol unit BFO-OFF switch to BFO
(17) Set control unit BFO-OFF switch to
and tune for zero beat. Then set BFO
BFO and tune for zero beat. Then set
OFF switch to OFF. Using the 50-
FIFO-OFF switch to OFF. Modulate
ohm probe, apply modulated signal
signal generator 30 percent at 400
to the base of Q4. If no sound is heard
cps.
or sound output is weak on either fre-
(18) Listen for audio in headset. If low or
quency range, check the alignment of
missing, check transistor Q3 and asso-
tuned circuit (para 314). Check RF
ciated circuit components.
transformers.
(19) Using 50-ohm probe, apply signal
(10) Use the test setup shown in figure
generator output signal to the base
of first RF amplifier Q1 (figs. 28 and 2-9
6b(1). Connect RF signal generator
or 2-9.1)Set signal generator for an out-
to input of test set. Do not use 50-
put of 100 microvolt.
ohm probe. Set signal generator for a
(20) Listen for audio in headset. If low or
200-kc unmodulated output signal at
missing, check transistor Q1 and asso-
a level of 50 microvolt.
ciated circuit components. Check con-
(11) Set control unit BFO-OFF switch to
dition of switch contacts on wafers
BFO and tune unit to 200 kc. Adjust
S1D and S1E. Check coils and asso-
signal generator for zero beat and
ciated components in 90-degree phase-
then set BFOOFF switch to OFF.
shift network between switch wafers
Modulate signal generator 30 percent
S1-D and S1-E.
at 400 cps.
(21) Setting control unit and signal gen-
(12) Listen for sound in headset. If sound
erator controls accordingly, listen for
is weak or missing, check condition of
a u d i o on the other two frequency
s w i t c h contacts on wafers S1-R,
ranges. If weak or missing, check
S 1 - N , S1-0, and S1C. Check RF
switches and 90-degree phase-shift
transformer T104 and alignment.
network.
(22) Connect signal generator to input of
controls for using test signals on the
test set (fig. 2-2). Do not use 50-ohm
400- to 850-kc and 850- to 1750-kc
probe. Tune signal generator for a
ranges. For each test signal, set BFO
200-kc unmodulated output signal at
OFF to BFO and tune for zero beat.
a level of 100 microvolt.
Then set BFOOFF to OFF and mod-
(23) Set test set GONIO DRIVE switch to
ulate signal generator output signal.
OFF. Adjust loop simulator control
(14) Listen for sound in headset. If low
for an indication on the LOOP SIMU-
or missing on any frequency range,
LATOR that is 90 degrees more than
check alignment (para 3-14) and RF
the indication on the test set BEAR-
transformer T105 or T106.
ING INDICATOR.
(15) For the following radiofrequency
(24) Set control unit. function switch to
tests, set control unit function switch
ANT. Set BFOOFF switch to BFO
to LOOP, GAIN control fully clock-
and tune signal generator for zero
wise, and range switch to 190- to 400-
b e a t in headset. Set BFO-OFF to
kc range. Tune to 200 kc.
OFF and set function switch to ADF
M o d u l a t e signal generator output,
(16) Using 50-ohm probe, connect signal
signal 30 percent at 400 cps.
generator output to the base of sec-
2-24
Change 1
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