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 TM 11-5805-387-34-2
MALFUNCTION/SYMPTOM
PROBABLE CAUSE
TEST PROCEDURE
INDICATION
YES
NO
(9) MODEM NOT TRANSMITTING VOICE
Defective: Mode selector switch S4. Connectors
MODE SELECTOR SWITCH AT VOICE
J3, J4, J2. 50-ohm mike keying
OR 85 HZ + VOICE.
Circuitry. Filter FL3. Circuit board A6.
Do all continuity and resistance checks with all power removed.
1. Check continuity of MODE SELECTOR
Continuity
Go to 2.
Replace
switch wafers S4B, S4C, S4G (fig. FO-8,
defective
fig. FO-11).
switch S4
2. Check continuity of connector J3 (local
Continuity
Go to 3.
Replace
operation), connectors J4 or J2 (remote
defective
connector
3. Remove transmitter module A3. Check
Continuity
Go to 4.
Replace
continuity of 50-ohm mike keying circuit
defective
components external to module A3: diode
component.
CR4, RCV/SEND switch S5, circuit board
A6, feed through capacitors C4, C9, C17,
C18 (fig. FO-11).
4. Connect AN/USM-207 across terminal 1 of
200 - 2,300 Hz
Continue test.
Continue test.
filter FL3. Speak Into mike.
Connect AN/USM-207 across terminal 3 of
200 - 2,300 Hz
Go to 5.
Replace
filter FL3. Speak Into mike.
defective filter
FL3 (para 3-9).
Do all continuity and resistance checks with all power removed.
5. Connect ME-26B/U between pin C of
Continuity
Go to 6.
Replace
connector J3 and terminal 7 of board A6.
defective
Check for continuity.
board A6
6. Connect ME-26B/U between pin C of
Continuity
------------
Replace
connector J2 and terminal 4 of board A6.
defective
Check for continuity.
board A6
3-11
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