RECEIVE TTY MALFUNCTION

TM 11-5805-387-34-2

MALFUNCTION/SYMPTOM

PROBABLE CAUSE

TEST PROCEDURE

INDICATION

YES

(9) RCV LEVEL READING ON TEST METER,

Defective: Circuit board A7.

BUT NO DISCRIMINATOR READING.

ABNORMAL SCOPE DISPLAY.

Set MODE SELECTOR switch to 850 HZ.

Input signal

-----------

Replace

Check for signal continuity across terminal

present

defective

8 or 9 of board A7 (fig. FO-8).

board A7

(para 2-10).

(10) RECEIVE TTY MALFUNCTION

Defective: Mode selector switch S4. Filter FL4.

Relay K1. Filter FL6. Filter FL7.

Recover module A4.

Do all continuity and resistance checks with all power removed.

1. Check continuity of MODE SELECTOR

Continuity

Go to 2.

Replace

switch wafer S4D (fig. FO-8).

defective

switch S4

(para 3-8).

2. Connect TS-799A/UGM-1 (para 2-4)

and test cable No. 3.

Set MODE SELECTOR switch to 85 HZ

Input signal

Go to 3.

Replace

DIVERSITY. Check for signal continuity

present on

defective

across terminal 2 of filter FL4 (fig.

AN/USM-281A

filter FL4

FO-8).

(para 3-9).

3. Check for signal continuity across terminal

Input signal

Go to 4.

Replace

4 of filter FL4.

present on

defective

ANIUSM-281A

filter FL4

(para 3-9).

2-17