MODEM NOT TRANSMITTING EITHER VOICE OR TTY.

TM 11-5805-387-34-2

MALFUNCTION/SYMPTOM

PROBABLE CAUSE

TEST PROCEDURE

INDICATION

YES

(5) MODEM NOT TRANSMITTING EITHER

Defective: Transmitter module A3. Circuit board A6.

VOICE OR TTY.

RCV-SEND switch S5.

1. With TS-799A/UGM-1 and test cable no. 3

Go to 2.

Replace

connected (para 2-4) make the

defective

following tests across OUTPUT of

module A3

transmitter module A3 (internal NORM/REV

(para 2-8).

switch at NORM) with the AN/USM-207:

MODE SELECTOR switch

850 Hz

SPACE: 2,425 Hz 25

MARK: 1,575 Hz 25

85-Hz modes

SPACE: 2,847.5 Hz 2

MARK: 2,762.5 Hz 2

VOICE

200-2,400 Hz

Do all continuity and resistance checks with all power removed.

2. Connect ME-26B/U between pin 1 of XA3

Continuity

Go to 3.

Replace

and terminal 2 of board A6; check for

defective

continuity.

wiring.

3. Check for continuity between terminals 2

Continuity

Go to 4.

Replace

and 13 of board A6; between terminals 14

defective

and 15 of board A6.

board A6

(para 2-10).

4. Set RCV/SEND switch to SEND.

Continuity

--------------

Replace

Connect ME-26B/U between SEND

defective

POST and CENTER POST. Check for

switch S5

continuity. (fig. FO-8)

(para 3-8).

2-13