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Page Title:
Checking Filament and High-Voltage Circuits for Opens and Short Circuits |
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  Tool or test equipment
Technical manual
name
Common
Tool Equipment TK-21/G . . . . .
....................
Tool equipment
Meter Test Set TS682A/GSM-1. . . .
........
TM 11-2535B
Test meter
Multimeter AN/URM-105 . . . . . .
......
TM 11-6625-203-12-35
Multimeter
Test Set, Electron Tube AN/USM-31
.......
Navships 91734
Tube tester
TM 11-6625-320-12
Voltmeter, Meter ME-30A/U . . . .
......
Voltmeter
(1) Measure the dc resistance between
15. Checking Filament and High-Voltage
terminal 34 of the 5-volt heater wind-
Circuits for Opens and Short Circuits
ing 3335 of transformer T2 (fig. 4
and 12) and ground.
Trouble in Test Set, Electron Tube TV2(*)
(2) The resistance should be 250,000 ohms.
, `U often can be detected by checking the dc
If the resistance is low or zero, the
resistance of the filament, plate, screen, bias,
plate high-voltage circuit is grounded.
and signal supply circuits (fig. 1113) before
d. Screen Supply Circuit.
power is applied to the unit. Take all measure-
(1) Measure the dc resistance between pin
ments with the multimeter; proceed as follows:
7 of tube V3 (fig. 11) and ground.
a. Preparation.
(2) The resistance should be between
(1) Disconnect the power cord from the ac
9,500 and 12,000 ohms; this depends
supply.
on the setting of SCREEN fine control
(2) Remove the chassis from the case, and
R54. If the resistance reading is very
then remove the tubes.
high or infinite, potentiometer R54 or
(3) Set PLATE-SCREEN RANGE switch
bleeder resistor R55 is open. If the re-
S3 to position G.
sistance reading is very low or zero, the
(4) Depress PRESS TO TEST P4 switch
screen supply is short-circuited.
S19 to its locking position.
(3) Check filter capacitors C4A and C4B
(5) S e t the SHORT TEST switch to
and screen supply (dc load) windings
OPER. position,
15-25 of transformer T2 for possible
(6) Set the FUNCTION switch to TEST
short circuits.
position.
e. Bias Supply Circuit.
(7) Set the PRESS TO TEST P1, P2, P3,
(1) Measure the resistance between pin 1
P5, and P6 switches to neutral position.
or 6 and pin 7 (ground) of tube V2
(8) Set all SELECTORS switches to 0
(fig. 11). With BIAS RANGE switch
position.
S2 in the 50 (50-volt) position, the
(9) Set the FILAMENT RANGE switch
resistance should be approximately
to OFF position.
7,000 ohms. With BIAS RANGE switch
b. Filament Circuit.
S2 in another position, the resistance
(1) Measure the dc resistance between ter-
will be considerably lower, but it should
minals 3 and 22 at the secondary of
be several thousand ohms. If the resist-
ance is very high or infinite, the wiring
(2) The resistance should be about 20
may be open or one of the bias voltage-
ohms. An infinite reading indicates
divider resistors R34, R26, R27, or R28
that there is an open secondary wind-
or BIAS fine control R29 may be open.
ing or a faulty connection at one of the
If the resistance is very low or zero,
terminals.
the bias supply is short-circuited.
(3) To detect a break, check the dc resist-
(2) Check filter capacitor C3 and the wir-
ance from terminal to terminal. If the
ing to bias supply rectifier tube V2 for
resistance is zero across any two ter-
short circuits.
minals, the circuits across the winding
f. Signal Supply Circuit.
are short-circuited or the winding itself
(1) Measure the dc resistance between ter-
is short-circuited.
c. Plate Supply Circuit.
minals 29 and 30 of the signal supply
AGO 1428A
17
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