Table 4-6. Performance and Troubleshooting Test for the -48 Vdc Power Supply SM-F-935778-Continued

TM 11-5895-1123-34

Step

Test setup instructions

Normal indication

If indication is abnorma

h. On the test fixture, connect the positive lead on the

-47 vdc minimum -48, -49,

Replace A1.

digital multimeter to J2M and the ground lead to

etc., are acceptable.

J2K and observe the indication on the digital mul-

timeter.

i. Remove the digital multimeter leads from the test

fixture and set the controls on the digital multime-

ter as follows:

FUNCTION

ACV

RANGE

200

j. On the test fixture, connect the leads from the digital

multimeter across J1A and JIC and adjust the

variac for an indication of 115 + 1 vac as indicated

on the digital multimeter.

k. Remove the digital multimeter leads from the test

fixture and set the controls on the digital multime

ter as follows:

FUNCTION

DCV

RANGE

200

i. On the test fixture, connect the positive lead from the

digital multimeter to J2M and the ground lead to

J2K.

m. On the test fixture, set the LOAD switch to the OFF

-49.5 vdc maximum, that is,

Replace A1.

position and observe the reading on the digital

-49.3, -49.4, etc., are ac-

multimeter.

ceptable.

Ripple Test:

a. On the test fixture, set the LOAD switch to the ON

position.

b. On the oscilloscope, set the controls as follows:

VERT MODE

CH1

AC GND DC

CHI VOLTS/DIV

20 m

(with

lox

probe)

HORIZ DISPLAY

A and B TIME/DIV

5ms

A TRIGGER TRIG -MODE

AUTO

A TRIGGER COUPLING

A TRIGGER SOURCE

NORM

A TRIG HOLDOFF

NORM

c. On the test fixture, connect the oscilloscope probe to

0.05 volts peak-to-pealk maxi- (1) Check and replace, if

J2K and ground lead to J2M and measure the

mum

necessary, A2.

ripple voltage (if any) as displayed on the oscillo-

(2) Replace A1.

scope.

4-12