Section VI
Paragraphs 6-14 to 6-15
THE AUDIO SIGNALS
AUDIO SIGNALS
AUDIO
TUBES
SELECTOR
AT AUDIO OUT
USED
JACK
POSITION
9960 cps FM and
V1401, V1402,
VOR
AUDIO SELECTOR at 9960 FM
V1406, V1408A
30 cps variable
and V1409.
phase (figure 6-1).
is inoperative the tubes used in the circuit that pro-
LOC
V1401B, V1402,
9960 cps FM and
duces the faulty audio signal should be checked. If all
V1406, v1407,
30 cps reversible
the audio signals are faulty, tubes used in circuits
phase (figure 6-2).
V1408A and
common to all audio signals should be checked. When
V1409
checking for lighted tube heaters note that the fila-
ment of V1510 on the univerter chassis is in series
90 cps and 150 cps V1404 and
TONE
with V1404 and V1405 heaters and therefore should
V1405
LOC
also be checked when V1404 and V1405 are not lit.
V1404 and
GLIDE
90 cps and 150
audio signals are faulty or not present.
SLOPE
V1405.
cps.
NOTE
V1405 and
1000~
1000 cps.
V1407A.
Tubes V1506, V1507, V1508 and V1509 on the
r-f chassis are common to all audio signals
V1401 and
30 ~
30 cps variable
and should also be checked with V1408B when
phase.
V1402.
VAR
no audio signals appear at the AUDIO OUT jack.
V1401B, V1402,
9960 FM
9960 cps fre-
6-15. VOLTAGE CHECK. After performing the wave-
V1406, V1407,
quency modulated
form and vacuum tube check and the trouble is isolated
V1408A and
at 30 cps (fig-
to a particular circuit, isolate the trouble further by
V1409.
ure 6-4).
signal tracing the fault y circuit. Use a Ballantine
90~
Model 300 electronic voltmeter or equivalent and com-
V1405.
90 cps.
pare the measurements with the typical a-c voltages
listed in table XII.
V1404.
150 cps.
150~
NOTE
The following measurements were made with
a Ballantine Model 300 electronic voltmeter
under the following conditions: Line voltage
set to 21 volts, NAV-GS switch at NAV, MEGA-
CYCLES control on 114.9, VOR control at 0,
LOC-GS control at center position, and meter
red lined with CARRIER SET control.
1
AUDIO SELECTOR SETTING
TEST
TERMINAL
POINT
COMPONENT
NO.
V1401
6
15.0
1
V1402
15.0
6
V1402
15.0
2
V1403
1.68
7
V1403
1.68
1
V1403
25.0
6
V1403
25.0
T1401
4
6.3
7
T1401
6.3
10
T1401
3.0
T1401
8
3.0
V1401
3
4.65
7
V1407
0.27
