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|  Step
Symptom
Probable
trouble
Correction
Check continuity of wire lead from
Cl to terminal 14 of connector
P501 (fig. 72). Repair connec-
t i o n s , if necessary.
Check for continuity from feedthru
capacitor C1 to chassis ground.
If infinite resistance is indicated,
suspect R6 and/or coil of relay
K1 for open circuit. Replace
defective component.
6
Meter pointer deflects to left of 0
Defective detector and electrom-
Replace defective detector and elec-
eter assembly A501 (fig. 72).
t r o m e t e r sealed assembly with
DECIBELS in both positions of
one known to be operating satis-
FREQUENCY RANGE-MC band
factorily in another tuning unit.
switch.
I f this replacement remedies
t r o u b l e , reinstall good detector
a n d electrometer assembly in
original tuning unit. Install new
A501 assembly in tuning unit 4.
Monitor output signal by plugging
Dirt or other foreign matter has
Warning: Cleaning compound is
7
lodged itself between rotor and
headset, through headset cord,
flammable and its fumes arw toxic.
stator plates of TUNING capac-
into PHONES jack. Intermittent
Do not use it near a flame; provide
scratchy sound is heard while
adequate ventilation.
scanning throughout either 400-
Flush or clean segments of variable
700-mc or 700-1,000-mc band.
capacitor C520 (for 400-700-mc
tuner) or C510 (for 700-1,000-mc
tuner). Use cleaning compound.
Same as symptom 7 above - - - - - - -
shorting between certain seg-
8
Refer to alignment procedure (para
ments of bent rotor plates and
fixed stator plates of TUNING
ment tool to bend rotor segment
which makes contact with stator
capacitor,
plate. Be careful when making
this adjustment and check rf out-
put over band to be sure that
a l i g n m e n t is satisfactory.
Defective crystal mixer CR501
9
Onscale meter indications are
Replace mixer with another crystal
diode known to be in satisfactory
p r e s e n t , but full-scale pointer
operating condition. If this does
deflection cannot be obtained
n o t remedy trouble, suspect rf
throughout each band, even with
amplifier tube V501 or V503,
GAIN control rotated fully
depending on band in use.
clockwise while rotating TUNING
control throughout each frequency
Defective or marginal electron
Replace tube with another coplanar
range.
tube V501 (for 700-1,000-mc
triode known to be In satisfactory
operating condition. (See fig. 49
tuner) or V503 (for 400-700-
mc tuner).
for identification of V501 and
V 5 0 3 electrodes.)
145
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