TM 11-5826-225-35
Procedure
indication
Item
Align network (para 3-14).
Push-pull RF amplifier and
mixer coupling network
out of alignment.
Align network (para 3-14),
Sense antenna input net-
work out of alignment.
Check continuity through contacts of switch
Switch wafers not making
contact.
Check transistors Q30 and Q3l (fig. 2-6).
9
Regulated power supply
Make voltage measurements (fig. 2-17).
defective.
While receiver switches frequency ranges,
Receiver muting circuit
N o i s e heard in headset
10
check positive dc voltage, on base of agc
c o n n e c t e d in PHONE
amplifier Q16 (fig. 2-3). Base voltage
jack on test set when
should rise sharply. If not, replace diode
receiver switches fre-
CR5.
quency. ranges.
While receiver switches frequency ranges,
switch w a f e r S 1 - M n o t
Receiver does not switch
11
check for presence of +27.5 volts on con-
or
closing dc voltage circuit
ranges
frequency
tacts of rear switch wafer S1M (fig. 2-8),
to motor B2.
functions.
Clean switch if necessary.
Check transistors (fig. 2-6).
Servo amplifier Q26, Q27,
12
Receiver does not tune to
Make voltage measurements ( fig. 2-17).
Q28, or Q29 defective.
to a radio station.
Check capacitor (fig. 2-6)
13
Capacitor C74 coupled to
Tuning servo does not
control winding of tuning
hold station frequency,
servo motor.
Adjust Rlll (para 3-10).
Tachometer feedback vari-
Tuning servo hunts
14
able resistor R111 out of
adjustment.
Note. Unless otherwise indicated for items 15 through,
18, set control unit and test equipment controls as
follows :
(1) On tbe, test set, place DC POWER to ON, GONIO
DRIVE to ON. and loop simulator control for an
indication on LOOP SIMULATOR 90 degrees more.
than indicated on HEARING INDICATOR.
(2) Tune signal generator to 200 kc with an RF
Output of 50
microvolts
unmodulated.
(.3) On the control unit, set function switch to ANT,
range switch to 190-400, GAIN to maximum clock-
wise position, BFO-OFF to BFO, and TUNE for
zero-beat on 200 kc. After zero-beat, set BOF-OFF
to OFF and function switch to ADF.
Using oscilloscope, check for waveforms on
Loss of 110-cps reference
When test set LOOP SIM
15
base and collector of Q23 (fig. 2-7). If
phase voltage on refer-
ence w i n d i n g o f servo
present, compare waveforms
taken
with
for 90-degree indication
those shown in figure 2-18.
motor B5 because of de-
from indicated bearing
fective
110-cps
amplifier
BEARING INDICA-
stage.
TOR rotates hut does
not reach a null.
Make voltage measurements on stage of Q23
(fig. 2-17).
Using transistor tester, check Q23.
2-20
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