Figure FO-16. MAC Control Fault Isolation Flow Chart

TM 11-5865-215-13

WITH OSCILLOSCOPE, CHECK FOR

PULSE ACTIVITY AT A3-106

REPLACE

CCA Al

AND AT A3-107

1. CONNECT CHANNEL D OF A 4-TRACE OSCILLOSCOPE TO A3-106 (0671). THE NEGATIVE GATE ON CHANNEL D

IS THE TEST INTERVAL (REFER TO FIGURE A). INTERNALLY SYNC THE OSCILLOSCOPE WITH THE NEGATIVE

EDGE OF THIS INPUT. EXPAND THE OSCILLOSCOPE SWEEP SO THAT THE NEGATIVE GATE FILLS THE ENTIRE

WIDTH OF THE CHANNEL D TRACE.

2. CONNECT THE OSCILLOSCOPE CHANNEL C TO A3-102

3. ROTATE THE RECEIVER CONTROL MGC CONTROL FULL CCW.

DURING THE TEST INTERVAL (DETERMINED

4. OBSERVE CHANNEL C TRACE IS HIGH

CHANNEL D).

5. SLOWLY ROTATE MGC CONTROL CW, OBSERVING 16

HIGH-TO-LOW EXCURSIONS OF CHANNEL C. WHEN THE

MGC CONTROL IS FULL CW CHANNEL C IS LOW

CHANNEL A

OV).

6. CHANGE THE OSCILLOSCOPE CHANNEL D LEAD TO

A3-107 (0672).

7. CONNECT CHANNEL B OSCILLOSCOPE LEAD TO

CHANNEL B

A3-101 (1621), AND CHANNEL 4 OSCILLOSCOPE LEAD

REMOVE AND

TO A3-1OO (1622).

REPLACE CCAS

8. ROTATE MGC CONTROL FULL CCW. OBSERVE CHANNEL

Al AND A5

A, B, AND C TRACES ARE ALL HIGH DURING THE TEST

CHANNEL C

INTERVAL (DETERMINED BY CHANNEL D).

9. SLOWLY ROTATE THE MGC CONTROL CW. OBSERVE THE

FOLLOWING NUMBER OF HIGH-TO-LOW EXCURSIONS ON

THE OSCILLOSCOPE DURING THE TEST INTERVAL.

CHANNEL D

1. WITH A VOLTMETER CONNECTED

OSCILLOSCOPE TRACE

NO. OF EXCURSIONS

AND

BETWEEN CCA A3-69

(-), ROTATE THE MGC CON-

CHANNEL C

FIGURE A

TROL FROM FULL CCWTO FULLCW.

CHANNEL B

2. OBSERVE VOLTAGE MOVES FROM

CHANNEL A

TO OV

10.

WHEN THE MGC CONTROL IS FULL CW, ALL

BE LOW.

(1623).

11.

CHANGE THE CHANNEL A PROBE TO

12.

ROTATE MGC FULL CCW. OBSERVE THAT THE CHANNEL A TRACE IS HIGH.

OBSERVING THAT CHANNEL A CHANGES FROM HIGH TO LOW AS THE MGC

13.

ROTATE MGC CONTROL

AS MGC IS ROTATED

CONTROL GOES THRU ITS MIDPOINT POSITION. THE CHANNEL A TRACE REMAINS

FULLY CW.

REPLACE

MGC CONTROL

YES

REMOVE AND

REPLACE CCA A3

EL3RJ061

Control Fault

Isolation Flow