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|  Probable
trouble
Correction
Symptom
Step
2
Meter indications are present when
Defective relay K2 or resistors
Same as for tuning unit 2, step 2.
SIGNAL ATTENUATOR DB con-
R1 through R5 in if. step atten-
If. step attenuators are identical
trol is rotated to 0 SUBST.
uator AT401 (fig. 66).
and interchangeable in tuning
ONLY, but pointer cannot be
units 2, 3, and 4.
zeroed in 20, 40, 60, and 80,
even with GAIN control set fully
clockwise.
Defective relay K1 in if. step
3
Meter indications are present when
Same as for tuning unit 2, step 3.
SIGNAL ATTENUATOR DB
attenuator AT401 (fig. 66).
switch is rotated to 0 SUBST.
ONLY and to 20, but pointer can-
not be zeroed at 40, 60, and 80.
Defective crystal mixer CR401
4
Replace CR401 with another crystal
On scale meter indications are
p r e s e n t , but full-scale pointer
diode known to be in satisfactory
deflection cannot be obtained
operating condition. If this does
throughout the band, even with
n o t remedy trouble, suspect rf
GAIN control rotated fully clock-
amplifier tube V401.
wise during rotation of TUNING
Defective or marginal electron
Replace V401 with another coplanar
control throughout the 200-400
tube V401 (fig. 69).
triode known to be in satisfactory
m c range.
operating condition. (See fig. 49
for identification of V401 ele-
ments.)
Defective detector and electrom-
Meter pointer deflects to left of O
5
Replace defective detector and elec-
eter assembly A401 (fig. 68).
t r o m e t e r sealed assembly with
DECIBELS instead of showing
o n s c a l e indications.
one known to be operating satis-
factorily in another tuning unit.
I f this remedies trouble, reinstall
known good detector and elec-
t r o m e t e r assembly in original
tuning unit. Install new A401
assembly in tuning unit 3 (fig.
Warning: Cleaning compound is
Dirt or other foreign matter has
6
Monitor output signal by plugging
lodged itself between rotor and
h e a d s e t , through headset cord,
flammable and its fumes are toxic.
stator plates of 3-gang TUN-
into PHONES jack. Intermittent
Do not use it near a flame; provide
ING capacitor (C402, C404,
adequate ventilation.
scratchy sound is heard while
and C413) in rf tuner (fig. 69).
scanning throughout the band
Flush or clean segments of variable
(rotating TUNING dial over the
capacitors C402, C404, and C413
200-400-mc frequency range).
with cleaning compound.
135
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