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|  Correction
Probable
trouble
Step
Symptom
somewhat less than 150 volts,
depending on setting of V503 ADJ
control R508 (fig. 72). No voltage
at C521 indicates defect in vari-
able resistor R508, rf choke
L521, and/or in wire lead which
is soldered to P501, terminal 2.
Replace defective component and/
or repair lead connection.
Replace L516 (fig. 73).
Lack of heater power at pin 4 of
oscillator tube V504.
With power removed, check rf
Lack of plate potential at pins 1
choke L518, feedthru capacitor
and 7 of oscillator V504 (fig.
C526, and/or fixed resistor R511
50) .
(A, fig. 73). Replace defective
part.
Check bypass capacitor C518, feed-
Lack of 6.3-volt heater power at
p r o t r u d i n g heater terminal of
thru capacitor C517, and rf choke
rf amplifier V503 (fig. 50).
L512 (A, fig. 73). Replace defec-
tive part.
Check R507 (B, fig. 73) and replace
Lack of anode potential at rf
amplifier V503 (fig. 50).
i f necessary.
Replace with crystal diode known to
Defective crystal mixer CR502
(A, fig. 73).
be in satisfactory operating con-
dition.
Check J503 and P505 for secure
Poor or no connection between
Meter indications are present at
3
mechanical and electrical connec-
400-700-mc of FREQUENCY
output jack J503 of coaxial
tion.
switch S501 and mating plug
RANGE-MC switch, but cannot
P505 of cable assembly W502
be obtained at 700-1,000 mc.
Check J506 and P506 for secure
Poor or no connection between
mechanical and electrical connec-
J506 on 700-1,000-mc rf tuner
tion. If this does not remedy
trouble, suspect defect within
of coaxial cable assembly
W502.
coaxial switch S501.
Remove operating power and dis-
Faulty contacts in coaxial switch
connect plug P503 from input
S501 (fig. 72).
jack J502 on coaxial switch. Also
disconnect P505 from output jack
J503 on coaxial switch. Use ohm-
meter to check for continuity
from coaxial switch jack J502 to
jack J503.
Defective V501 or V502 (A, fig.
Replace V501 or V502.
74) .
Zero resistance eliminates S501 as
s o u r c e of trouble. Infinite resist-
ance indicates defective coaxial
switch. Replace defective compo-
nent.
Lack of 6.3-volt ac power source
Check for 6.3-volt ac source of
in 700-1,000-mc rf tuner (fig.
heater power at protruding ter-
minal of feedthru capacitor C540
ckeck for 6.3-volt ac from each
terminal of L524 to chassis
ground. If this does not remedy
trouble, search for open wire
lead connection between one ter-
minal of rf Choke L524 and junc-
tion of rf choke L545 (fig. 72)
with bypass capacitor C531.
R e p a i r wiring.
Lack of +105-volt power souroe
Check for +105-volt source of
to plate circuit of oscillator
power to oscillator V502 from
protruding terminal of feedthru
capacitor C511 to ground. If no
143
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