TM 11-6625-2958-14&P

 

Table 5-6. Series Regulator Troubleshooting, Low Voltage Condition (Continued)

 

 

 

 

 

 

 

 

 

 

STEP

 

ACTION

 

 

RESPONSE

 

PROBABLE CAUSE

 

 

 

 

 

 

 

 

 

 

 

2

Check

conduction

of driver

a. Output

voltage

remains

low.

a. A4Q102 open, thermal

 

 

A4Q102 by shorting A4Q101

 

 

 

 

 

switch A4TS101 open.

 

 

emitter (TP100) to base

b.

Output

voltage

rises.

 

b. Remove short. Proceed

 

 

(TP45).

 

 

 

 

 

 

 

 

 

 

 

 

to Step 3.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

Check

turn-off

of

error am-

a,

Output

voltage

remains

low.

a. A4Q101 or CR44 shorted.

 

 

plifier A4Q10 1 by connecting

b.

Output

voltage

rises.

 

b. Remove short. Proceed

 

 

base (TP45) to Q42 base

 

 

 

 

 

 

 

 

to Step 4.

 

 

(TP44).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

Check

turn-off

of

error am-

a. Output

voltage

remains

low,

a. Q42 shorted.

 

 

plifier

Q42 by

connecting

b.

Output

voltage

rises.

 

b. Remove resistor. Pro-

 

 

base (TP44) to +11V supply

 

 

 

 

 

 

 

 

teed to Step 5.

 

 

(TP66) through a 1K Ω resistor.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

Isolate

fault to either con-

a,

Output

voltage

rises.

 

a. Z1 defective, open

 

 

stant voltage comparator or

 

 

 

 

 

strap between A6 and

.

 

constant current comparator

 

 

 

 

 

A7, or shorted A5R123

 

 

 

 

 

 

 

 

by opening the cathode of

 

 

 

 

 

or A5R124.

 

 

CR20.

 

 

 

b. Output

voltage

remains

low.

b. Reconnect lead and

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

proceed to Step 6.

 

 

 

 

 

 

 

 

 

 

 

6

Check

conduction

of mixer

a. Output

voltage

remains

low.

a. Q41 or CR40 open, Q40

 

 

amplifier Q41

by

connecting

 

 

 

 

 

shorted.

 

 

base (TP40) to +S terminal.

b. Output

voltage

rises.

 

b. Remove short. Proceed

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

to Step 7.

 

 

 

 

 

 

 

 

 

 

 

7

Check

conduction

of con-

a. Output

voltage

remains

low.

a. Z1 defective, R1

 

 

stant voltage comparator Z 1

 

 

 

 

 

shorted.

 

 

by shunting R110 with a 10K

b. Output

voltage

rises.

 

b. A5R121 and A5R122

 

 

ohm resistor, or by installing

 

 

 

 

 

 

 

 

shorted, open strap’

 

 

a 10K Ω resistor in R110 po-

 

 

 

 

 

 

 

 

 

 

 

 

between AZ and A3, R5

 

 

sition

if resistor

is not in-

 

 

 

 

 

 

 

 

 

 

 

 

open, C2 shorted, CR7

 

 

stalled

in the

supply.

 

 

 

 

 

 

 

 

 

 

 

 

shorted.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5-7.Preregulator Troubleshooting (Refer to Waveforms in Figure 7-9)

STEP

ACTION

RESPONSE

PROBABLE CAUSE

 

 

 

 

 

 

 

 

Adifferential oscilloscope must be used for these tests in order to avoid a potentially dangerous shock hazard. Floating a single-ended oscilloscope for these tests is not recommended, because it may result in the oscilloscope chassis being at 230Vac line potential.

1

Connect oscilloscope be-

a. Normal

waveform.

 

tween TP89 (+) and TP86 (-).

 

 

 

 

b. Little or

no voltage.

 

 

 

 

a. Defective A2CR1, R88, CR88, A2L1A/A2L1B, T1, A2C1, A2R1.

b. Proceed to Step 2.