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TROUBLESHOOTING CHART (Cont)
Up
TM-11-5805-387-34-2 Modem Radion Teletypewriter MD-522A/RC (NSN
Next
TEST POINT MEASUREMENTS
TM 11-5805-387-34-2
MALFUNCTION/SYMPTOM
PROBABLE CAUSE
TEST PROCEDURE
INDICATION
YES
NO
(17) MODEM NOT TRANSMITTING VOICE.
Defective: Mode selector switch S5. Connectors
J3, J4, J2. 50-ohm mike keying cir-
cuitry. 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
operation) (fig. FO-8, fig. FO-11).
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 ME-26B/U between pin C of
Continuity
Go to 5.
Replace
connector J3 and terminal 7 of board A6.
defective
Check for continuity.
board A6
5. Connect ME-26B/U between pin C of
Continuity
------------
Replace
connector J2 and terminal 4 of board A6.
defective
Check for continuity.
board A6
(18) ABNORMAL SCOPE PRESENTATION
Defective: Resistor R3.
BUT NORMAL DISCRIMINATOR IN-
DICTION ON TEST METER.
DEATH ON CONTACT may result from contact with the terminals of R3.  With module A2
operating, -800 volts dc appears on scope intensity control resistor R3.  Do the following
continuity check with all power removed.
Remove scope module A2 (refer to para
Continuity
------------
Replace
2-8). Check continuity of variable resistor
defective
R3 (fig. FO-8).
resistor R3
3-18

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