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|  Confection
Probable
trouble
Symptom
Step
perform continuity and infinite
resistance checks, as outlined in
p r o c e d u r e immediately above.
Check for secure connections of
No driving power from if. pre-
cable assembly W403. Be sure
amplifier to if. step attenuator
that connector plug P409 (fig. 68)
AT401 (fig. 68).
mates if. preamplifier output jack
J408 (fig. 70), and that plug P41O
mates if. step attenuator jack
AT401J1 (fig. 68). If this does not
remedy trouble, disconnect cable
assembly W403 and perform con-
tinuity and infinite resistance
checks as outlined for cable
assembly W401.
No driving power from if. step
Check for secure connection of con-
attenuator AT401 (fig. 68) to if.
nector plug P412 to mating jack
AT401J2 on if. step attenuator
amplifier (fig. 71).
coaxial cable is soldered to
termination CP411 at input to if.
amplifier (fig. 71). Check and
repair solder connection if open
circuit is suspected. If this does
not remedy trouble, suspect if.
p r e a m p l i f i e r and/or if amplifier.
F a u l t y if. preamplifier circuit
Troubleshoot by signal substitution
technique (para 73). Check V403,
V404, and V405 (fig. 68).
Troubleshoot by signal substitution
Faulty if. amplifier circuit (fig.
technique (para 73). Check V406
through V410 (fig. 68).
Check for 6.3-volt ac heater power
Inoperative rf tuner (fig. 69) ----
at protruding terminal of feedthru
capacitor C411 (fig. 69). Repair
wire lead connection from feed-
thru capacitor C430 at electron
tube side of if. amplifier. If this
does not remedy trouble, discon-
nect oprating power and check
rf choke L414 for open circuit.
Replace L414 if defective. Replace
V402.
Check for +105-volt source of power
to oscillator V402 from protrud-
ing terminal of feedthru capacitor
C422 to Chassis ground. If no
voltage is indicated, check R409
for open circuit. Repair wire
lead connection from high-volt-
age terminal of R409 to connec-
tor P401 (fig. 68), terminal 3,
i f necessary.
Check for B+ voltage to rf ampli-
fier V401 by measuring voltage
from protruding terminal of feed-
thru capacitor C410 to chassis
ground. Proper voltage will be
somewhat less than 150 volts,
depending on setting of V401 ADJ
control R405 (fig. 68). No volt-
age at C410 indicates defect in
R402, variable resistor R405 or
R420, or in wire lead which is
soldered to P401, terminal 2.
Replace defective component and
or repair lead connection.
134
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