TM 11-5826-225-35
Note. After making the above tests, adjust
Using the 50-ohm probe, apply signal
variable resistor R90 in accordance with the
to test point TP2 (collector of Q11
instructions in paragraph 317. Remove
and network Z1).
ground from agc testpoint TP3.
L i s t e n for audio output signal in
(3)
headset. If no sound is heard, check
frequency tests at the mixer stage and work
network Z1, audio detector CR1, audio
back toward the antenna inputs.
limiter CR2, and associated circuit
(1) Unless otherwise indicated, use the
components.
test setup described in paragraph 2
Apply signal generator RF signal to
(4)
6b(l).
the base of transistor Q11. Audio out-
put signal level should increase. If
fully clockwise. Ground age testpoint
no sound is heard or sound is low,
TP3.
check transistor Q11 and associated
circuit components.
unmodulated output signal at a level
A p p l y signal to the base of Q10.
(5)
of approximately 5 microvolts. Using
Audio output signal should increase.
50-ohm probe, apply signal to test-
If not, check transistor Q10, IF trans-
point TP4 connected to junction of
former T17, coupling capacitor C53,
capacitor C29 and contact number 3
and associated parts.
of front switch wafer S1-I (figs. 28
Adjust signal generator for an out-
(6)
and 213 or 2-13.1).
put level of 15 millivolts, Apply sig-
nal to the base of Q9. If no sound
(4) Set control unit BFOOFF switch to
is heard or sound output is low, check
BFO and function switch to ANT.
Adjust TUNE control for zero beat in
transistor Q9, IF transformer T16,
coupling capacitor C108, and asso-
headset then turn BFOOFF switch
to OFF.
ciated circuit components.
Using a jumper wire, ground agc test
(7)
point TP3. Adjust signal generator
an output signal modulated 30 per-
cent at 400 cps. If no sound is heard,
output signal to 250 microvolt and
check mixer Q5 and associated circuit
apply signal to base of Q8. If no
components.
sound is heard in headset or output
is low, check transistor Q8, IF trans-
(6) Using 50-ohm probe in series with
former T15, coupling capacitor C51,
signal generator output lead, apply
and associated circuit components.
200-kc RF signal to the base of RF
Adjust signal generator for an out-
amplifier 4 (figs. 2-8 and 2-11
(8)
o r 2-11.1.
put level of 10 microvolt and apply
(7) If no sound is heard or sound is low,
signal to base of transistor Q7. If no
check transistor Q4 and stage circuit
sound. is heard or sound is low, check
components.
C h e c k condition of
transistor Q7, IF transformer T14,
switch contacts on wafers S1P and
coupling capacitor C48, and asso-
S11. Check alignment of RF ampli-
ciated circuit components.
fier and mixer coupling network used
on the 190- to 400-kc range (para
Adjust signal generator output level
(9)
to 100 microvolt and apply signal to
and T10.
the collector of Q5 through the 50-
ohm probe. If audio output signal is
(8) Apply signal to the base of transistor
low or absent, check IF transformer
Q2. If no sound is hoard in headset,
T13, variable resistor R90, coupling
check transistor Q2 and associated
capacitor C110, and associated compo-
circuit components. Check condition
nents.
of switch contacts on wafer S1P.
Change 1
2-23
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