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

TM 11-5895-1123-34

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

Step

Test setup instructions

Normal indication

If indication is abnormal

Counterclockwise and cloc kwise directions are indi-

cated in terms of the UUT being set upside down with

the adjustment screws on the potentiometers facing

upward.

Overvoltage Adjustment:

a. Connect the equipment as shown in figure 4-7.

b. Set the control on variac fully counterclockwise.

c. On the side of the test fixture, set both the LOAD

and LINE switches to the ON position.

d. Connect the equipment to a 1155 vac source and

turn on the equipment.

e. On the -48 vdc power supply (UUT), adjust the

TRIP SET potentiometer fully clockwise.

f. On the digital multimeter, set the controls as follows:

FUNCTION

ACV

RANGE

200

g. Connect the digital multimeter across J1A and J1C

on the test fixture.

h Adjust the variac for 1151 vac as indicated on the

115 1 vac

Replace A1 on the UUT.

digital multimeter.

i On the test fixture, remove the digital multimeter

leads from J1A and J1C.

j. On the digital multimeter, set the controls as follows:

FUNCTION

DCV

RANGE

200

k. On the test fixture, connect the positive lead of the

-40 to -60 vdc

Proceed to 1 below.

digital multimeter to J2M and ground lead to J2K

and observe the reading on the digital multimeter.

If indication is normal, proceed to n below.

l. On TB 1 of the UUT, connect the digital multimeter

-40 to -60 vdc

Remove the leads from

terminals

positive lead to terminal 3 and ground lead to ter-

2 and 5 on TB1 of the UUT and

minal 6. If indication is normal:

observe for normal

indication.

(1) Check and replace, if necessary, CR1 and return

If indications return to normal,

to a above.

replace A2 on the UUT and re-

(2) Check and correct, if necessary, shorted or opened

turn to a above. If indication

leads and pin connectors on the UUT between

remains abnormal, proceed to

pin K on J2 and terminal 6 on TB1 and also

m below.

between pin M of J2 and terminal 3 of TB1

(through CR1). Then return to a above.

m. On the digital multimeter, set thecontrolsasfollows:

115+1 vac

Check and correct, if necessary,

FUNCTION

ACV

shorted or open pin con nectors

RANGE

200

and wiring on the UUT be-

Measure the voltage across the IN terminals 1 and

tween pin A of J1 and IN ter-

2 on A1of the UUT.

minal 2 of A1and also between

If indication is normal, replace A1 on the UUT and

pin C of J1 and IN terminal 1 of

return to a above.

A1. Then return to a above.

n. On the UUT, loosen the locknut on the VOLTAGE

-50, +0, -0.2 vdc

On the UUT, remove the connec-

ADJUST on A1and adjust it for -50 +0, -0.2

tions from terminals 2 and 5 on

vdc indication on the digital multimeter.

TB1 and adjust the VOLT-

AGE ADJUST on A1while

observing for normal indications.

If normal indications appear, re-

place A2 and then return to a

above.

If indications remain abnormal,

replace A1 and then return to a

above.

o. While observing the digital multimeter, adjust the

Digital multimeter reads less

Replace A2.

TRIP SET potentiometer on the UUT until the

than -1 volt.

power supply just trips out.

p. On the UUT, turn the VOLTAGE ADJUST fully

counterclockwise.

4-10