TM 11-6625-2965-14&P

more useful to trace the loop from the series reg-

failures

occur more often at the higher power

ulator backwards a stage at a time, since loop

levels .

 

Table 5-4. High Output Voltage Troubleshooting

STEP

ACTION

 

 

RESPONSE

 

 

PROBABLE CAUSE

 

 

 

 

 

 

 

 

 

 

 

 

1

Check turn

off

of series

 

a. Output

voltage

remains

high.

a.

Series regulator

Q7

 

regulator by

shorting Q4

 

 

 

 

 

 

(or

Q6) shorted.

 

emitter to collector.

 

b. Output

voltage

decreases .

b. Remove short and proceed

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

to

Step 2.

 

 

 

 

 

 

 

 

 

 

 

 

2

Check turn on of Q4 by

 

a. Output

voltage

remains

high.

a.

Q4

open.

 

 

disconnecting

collector

 

b. Output

voltage

decreases.

b. Reconnect lead

and pro-

 

of Q3.

 

 

 

 

 

 

 

 

 

 

 

 

ceed to Step 3.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

Check turn off

of Q3 by

 

a. Output

voltage

remains

high.

a.

Q3

shorted.

 

 

disconnecting

collector

 

b. Output

voltage

decreases.

b,

Check Q1A for

short,

 

of Q1A.

 

 

 

 

 

 

 

 

 

 

 

 

Q1B for open. Check for

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

open strap between A6

 

 

 

 

 

 

 

 

 

 

and A8. Check R10 for

 

 

 

 

 

 

 

 

 

 

open.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table

5-5.

Low Output Voltage Troubleshooting

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

STEP

 

ACTION

 

 

 

 

 

RESPONSE

 

PROBABLE CAUSE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

Check

turn

on of

Q7

 

 

a. Output

voltage

remains low.

a.

Q7 (or Q6)

open.

 

 

(and Q6, if

included)

 

b.

Output

voltage

increases.

b. Reconnect

lead

and

pro-

 

by opening

 

the emitter

 

 

 

 

 

 

 

 

 

ceed to

Step

2.

 

 

 

of Q4 .

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

Eliminate the current

 

a. Output

voltage

increases.

a. Q10 shorted, R81 defec-

 

limit circuit

as a

source

 

 

 

 

 

 

tive .

 

 

 

 

 

 

of trouble

by discon-

 

b. Output voltage remains low.

b. Reconnect

lead

and

pro-

 

necting

the

 

anode

of

 

 

 

 

 

 

 

 

 

ceed to

Step

3.

 

 

 

CR16.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

Check

turn

off of

Q4

by

 

a. Output

voltage

remains low.

a.

Q4 shorted.

 

 

 

 

shorting Q3

emitter

to

 

b.

Output

voltage

increases.

b. Remove

the

short and

 

collector.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

proceed

to

Step

4.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5-11