TM 11-6625-2965-14&P

Table 5-5. Output Voltage Troubleshooting (Continued)

4Check turn on of Q3 by shorting Q1A emitter to collector

 

 

RESPONSE

 

PROBABLE CAUSE

 

 

 

 

 

 

 

a . Output

voltage

remains low

 

a. Q3 open

 

b. Output

voltage

increases

 

b, Check Q1A for open, QlB

 

 

 

 

 

for short. Check R10 for

 

 

 

 

 

short or open strap be-

 

 

 

 

 

tween A7 and A6

 

 

 

 

 

 

5-58 REPAIR AND REPLACEMENT

5-59 Before servicing a printed wiring board, refer to Figure 5-11. Section VI of this manual contains a tabular list of the instruments replaceable parts. Before replacing a semiconductor device, refer to Table 5-6which lists the special charac-

teristics of selected semiconductors. If the device to be replaced is not listed in Table 5-6,the standard manufacturers part number listed in Section VI is applicable. After replacing a semicon- ductor, refer to Table 5-7 for checks and adjustments that may be necessary.

 

 

 

Table 5-6.

Selected

Semiconductor

Characteristics

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

REFERENCE

 

 

 

CHARACTERISTICS

 

 

STOCK NO.

SUGGESTED

 

DESIGNATOR

 

 

 

 

 

REPLACEMENT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Q1

 

Matched differential amplifier. NPN Si. planar

 

1854-0229

2 N 2 9 1

G . E .

 

 

 

70 (min.) hFE ic = lmA, VCE = 5V, Ico = 0.01µA

 

 

 

 

 

 

 

 

@ Vcbo = 5 V ,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Q7

 

NPN Power

hFE = 35 (min.) @ Ic = 4A; VCE = 4V.

 

1854-0225

2N3055

R. C,A,

 

 

 

 

 

 

 

 

 

 

Table 5-7. Checks and Adjustments After Replacement of Semiconductor Devices

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I

REFERENCE

 

 

 

FUNCTION

 

 

 

 

CHECK

 

 

ADJUST

Q1

 

Constant

voltage

differential

amplifier

 

Constant

voltage (CV)

line

 

R6 or R8

 

 

 

 

 

 

 

 

 

and

load regulation.

Zero

 

 

 

 

 

 

 

 

 

 

 

volt

output.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Q3, Q4

 

Error

amplifiers

 

 

 

CV

load

regulation.

 

 

R30

 

 

 

 

 

 

 

 

 

CV

transient response.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Q7 (Q6)

 

Series

regulater

 

 

 

CV

load

regulation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Q8, Q9

 

Reference regulator

 

 

Reference circuit line

 

 

VR1, VR2,

 

 

 

 

 

 

 

 

 

regulation.

 

 

CR20

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CR1, CR2

 

Limiting

diodes

 

 

 

CV

load

regulation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CR8

 

Forward

bias regulator

 

 

Voltage

across diode

 

 

 

 

 

 

 

 

 

 

 

 

2.0

to 2.4 Volts.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5-12