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TROUBLESHOOTING CHART (Cont)
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TM-11-5805-387-34-2 Modem Radion Teletypewriter MD-522A/RC (NSN
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TROUBLESHOOTING CHART (Cont)
TM 11-5805-387-34-2
MALFUNCTION/SYMPTOM
PROBABLE CAUSE
TEST PROCEDURE
INDICATION
YES
NO
NOTE
Series regulators Q1, Q2, Q3 automatically cut off when +22 volt output of preregulator board A9
is shorted. Normal operation will resume when short is removed.
1. Connect ME-26B/U across terminal 5 on
+22 vdc.
Go to 2.
Replace
board A9 (or E-37 on panel); measure
0.5
defective
voltage.
board A9
2. Check transistors Q1, Q2, Q3 for shorts to
Shorts to
Replace
Go to 3.
ground.
ground
defective
transistor
3. Check transistors Q1, Q2, Q3 for open
Open
Replace
condition.
defective
transistor
(5) MODEM DOES NO KEY TRANSMITTER
Defective: RCV-SEND switch S5. Diodes CR1
CR2, CR3, CR4. CR6. Connectors J3,
J4 (remote operation). Connector J2
(local operation). Circuit board A6.
Do all continuity and resistance checks with all power removed.
1. Check continuity of RCV/SEND switch
Continuity
Go to 2.
Replace
(fig. FO-8).
defective
switch S5
2. Connect TS-352B/U to opposite ends of
Zero ohm in
Go to 3.
Replace
diode CR1; CR4; CR6. Measure forward
one direction,
defective
and reverse resistance of each diode
infinity or high
diode (para
(figure on next page).
resistance in
other direction
3-6

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