Section VI
Paragraph 6-11 to 6-13
When checking tube filaments, only apply
enough voltage with SET LINE TO 21V control
to note whether tube filaments are lit. Do not
remove tubes when the power is on. Tubes
are in series-parallel arrangements and with-
drawing one may damage others in the circuit.
a. If V1510 is not lit, check V1510 and V1404 and
V1405 in the audio chassis. If V1510, V1404 and
V1405 are good, resistor R1429 on the audio chassis
may be open.
b. If only one filament of V1511, V1512 and V1513
are lit and the tube is good, check the r-f choke in
series with the unlit filament.
c. If only V1510 is lit and the other three tubes on
the univerter chassis are good, resistor R1490 on the
audio chassis may be open.
quencies used in the univerter chassis, it is difficult
to isolate the faulty stage by signal tracing. If all
tubes in the univerter chassis are good yet there is no
r-f output during GS operation, check all r-f cables
and make voltage and resistance measurements to lo-
cate the faulty stage and component.
chassis may be isolated to the faulty circuit by check-
ing waveforms at test point
AUDIO OUT jack
J1408, for various positions of the AUDIO SELECTOR
switch. Connect an oscilloscope to the AUDIO OUT
jack and compare the waveforms with those given
below:
a. VOR. Appears as a wide sine wave band at 30
cps. See figure 6-1.
b.
LOC. Same as VOR except smaller 30 cps am-
plitude. See figure 6-2.
c. TONE LOC. Appears as composite 90 and 150
cps wave which varies with LOC-GS control. See
d. GLIDE SLOPE. Same as TONE LOC except that
amplitude is doubled.
e. 1000~. Appears as a 1000-cps sine wave.
f . 30~ VAR
Appears as a 30-cps sine wave
whose phase may be shifted with VOR control.
g. 9960 FM. Appears as a 9960-cps sine wave with
See figure 6-4.
h. 90~ Appears as a 90-cps sine wave.
i. 150~. Appears as a 150-cps sine wave.
