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Page Title:
Power Distribution Circuits and Components-continued |
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|  TM 11-5820- 509-35
Item
Indication
Probable trouble
Procedure
12
Filaments of power amplifier stage
a.
Filament circuit vacuum tube
a.
Check continuity of filament
do not Light.
open.
circuit within V101; replace tube
(para 3-14) if defective.
b.
Filament chokes L120 and L121
b.
Check continuity of chokes
defective.
L120 and L121 (normal 0.09
ohms). Replace if defective.
Note.
Make the following checks after unsoldering the filament lines from PA filter box FL2-14 and FL2-15. (Tag each wire).
c. Filament circuit in FL2
defective.
FL2-14 and from FL2-2 to FL2-
15, and test each terminal for
shorts to ground. Repair circuit
or replace C221, C208, C235,
C220, C207, or C234 if defective.
Note:
Reconnect the two filament lines to terminals FL2-14 and FL2-15 of the PA filter box.
d.
Filament bypass capacitors or
d.
Check continuity of R121
hum balance resistor or circuit
(normal 50 ohms); check con-
defective.
tinuity of circuit from L120 to
XV101-1 and L121 to XV101-7.
Repair circuit, or replace R121 if
defective.
Note.
Disconnect capacitors C103 and C104 from XVIO1 before proceeding with the following tests. (Tag each lead).
e. Filament bypass capacitors
e. Check C103 and C104 for
shorted to chassis ground.
shorts; replace if defective.
Note.
Reconnect capacitors C103 and C104 to the filament pins of tube socket XV101.
13
Dc bias voltage measured between
a. -32-volt dc bias circuit of PP-
a.
Perform adjustment routine of
A3J3 and chassis ground is not
3518/PRC-47 incorrectly ad-
-25 volts dc.
justed or defective.
3518/PRC-47, .or repair (para 3-
6) if defective.
b.
Fuse F4 (1/500A) (fig. 3-5) is
b.
Check and replace fuse F4, if
burnt out.
defective.
c.
Inductor L6 is open or shorted
c.
Check continuity of L6 (normal
to ground.
72.0 ohms): check L6 for shorts
to ground. Replace L6 if
defective.
d.
-32-volt bias circuit on main
d.
Check continuity from J1-23 to
chassis defective.
XF4-1, from XF4-2 to L6-1,
from L6-2 to J7-1. Repair as
required.
e.
-32-volt bias circuit in signal
e.
Repair CV-1377A/PRC-47
data translator A3 defective.
using procedure of paragraph 3-
6.
14
Dc bias voltage measured between
a.
-110-volt dc bias circuit of
a.
Perform adjustment routine of
J102 (fig. 3-5) and chassis is not
PP-3518/PRC-47 incorrectly
-110 volts dc.
adjusted or defective.
3518/PRC-47, or repair (para 3-
6) if defective.
b.
XMTR PWR switch S103 not
b.
Place S103 to XMTR PWR HI.
at HI position.
c.
XMTR PWR switch S103
c.
Check continuity of S103 (in HI
defective.
position) from S103-1 to S103-4
or S103-5. Rotate S103 to LO
position and check from S103.1
to S103-2. Measure resistance of
R107 {normal 100K ohms).
Repair circuit or replace S103 or
R107 as required.
3-79
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