Short-circuit tests
Isolating produre
Point of measurement
Normal indication (ohms)
Zero resistance indicates a short
Less than 1
Between pins 2 and 7 of tube
circuit in the filament winding.
socket XV5.
Check continuity of each wire to
Less than 1
Between pins 3 and 4 of tube
locate the short. High or in-
socket XV3.
finite resistance indicates an
open transformer filament wind-
ing or defective wiring between
Less than 1
Between pins 2 and 8 of tube
the tube socket and the trans-
socket XV4.
former.
A low resistance indicates a short
Infinite resistance
Between pin 2 of tube socket
circuit in the filament wiring.
V5 and chassis ground.
If resistance is low, check for
Infinite resistance
From pin 5 of tube socket XV5
shorted capacitor C8A or C8B.
to ground.
n e g a t i v e lead to chassis wrong
polarity on electrolytic capaci-
tors will give a false low reading.
If resistance is low, check capaci-
100,000
From pin 3 of tube socket XV5
tors C8C and C8D.
to ground.
If resistance is low, check for
150,000
From pin 6 of tube sockets XV1
defective screen bypass capaci-
and XV2 to ground.
tors C2A, C4A, or filter capaci-
tors C8C and C8D. If resistance
is higher than normal, check for
an open resistor in the voltage
regulator circuits.
8. Test Setup
ticular tests or adjustments (para 14 and
15). A 3 , 0 0 0 - o h m , l - w a t t r e s i s t o r i s
Bench tests of the rf amplifier require
connected across the OUTPUT terminals
c o n n e c t i o n to a power source and to
for all distortion measurements (para 19).
various test equipments. The power
source must be connected to the rf am-
9. Localizing Troubles
p l i f i e r for all dynamic-servicing pro-
a. General In the troubleshooting chart
cedures; the test equipment connections
(d below), procedures are outlined for
vary from test to test. Remove the top
localizing troubles to a particular stage
cover from the rf amplifier and make a
w i t h i n the rf amplifier. Parts locations
test setup as follows:
a. Connect the output terminals of Audio
diagram of the rf amplifier is shown in
Oscillator TS-382/U (or equivalent) to the
INPUT terminals of the rf amplifier so
urements are shown in figure 5. Depend-
that the ground lead on the audio oscillator
ing on the nature of the operational symp-
connects to the ground lead of the rf am-
plifier.
toms, one or more of the localizing pro-
b. Connect the OUTPUT terminals of
cedures may be necessary. When trouble
the rf amplifier as specified for the par-
has been localized to a particular stage,
9
