TROUBLESHOOTING CHART (Cont)

TM 11-5805-387-34-2

MALFUNCTION/SYMPTOM

PROBABLE CAUSE

TEST PROCEDURE

INDICATION

YES

(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

(para 3-8).

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

(para 3-8).

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

(para 2-10).

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

(para 2-10).

(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

(para 3-8).

3-18