Figure 5-4. Power Supply PP-3940A/G, Component Board A4, Parts Location Diagram.

TM 11-6130-247-14-1

Figure 5-4. Power Supply PP-3940A/G, Component Board A4, Parts Location Diagram.

wise. Indicator should be 0 volt ± 0.1.

wire turns further until meter indicates zero.

(3) Lock potentiometer A3R50 with Gyptol.

5-9.

Overcurrent

Protection

Network

d. Set CUR ADJ coarse and fine control potentiom-

Adjustment

eters R53A and R53B maximum clockwise, and adjust

load to between 4.15 and 4.25 amperes. CUR MODE

Perform the following whenever transistor A4Q38 is

replaced:

indicator DS3 should not light.

a. Set power supply POWER switch S1 to off and

e. If CUR MODE indicator DS3 lights, rotate

VOLT ADJ coarse and fine controls fully counterclock-

potentiometer R54 until VOLT MODE indicator lights

and CUR MODE indicator extinguishes.

wise.

f. Readjust potentiometer R54 until CUR MODE

b. Connect load set at 5 ohms across terminals 4 and

indicator lights and current drops slightly (but re-

5 on terminal board at rear of power supply.

mains within the 4.15- to 4.25-ampere range).

c. Unsolder resistor A4R99 and remove transistor

g. Lock with Gyptol.

A3Q16 from its snap out socket.

d. Insert ZM-16/U in place of resistor A4R99 with

5-8. Voltage Programing Adjustment

an initial setting of approximately 100 ohms.

e. Set power supply POWER switch S1 to ON.

a. Set POWER switch S1 to off and remove load and

ammeter.

f. Slowly turn VOLT ADJ coarse and fine controls

b. Remove link between terminal board terminals 1

until the output current rises to 135 percent of the

and 2 and insert Resistor, Decode ZM-16/U between

nominal value (5.4 amperes).

terminals 1 and 3 (voltage programing), adjusting

g. Adjust ZM-16/U until the power supply shuts

ZM-16/U for exactly 4,000 ohms.

off.

h. Set power supply POWER switch S1 to off. Insert

c. Set POWER switch S1 to ON and adjust potenti-

ometer R69 to give an output voltage of 40 volts dc

the nearest standard resistor value for the ZM-16/U

&0.20, This calibrates the voltage programing to 100

resistance reading (22 to 100 ohms).

ohms/volt.

i. Perform e and f above. Power supply should turn

off when the current reaches 130 to 140 percent of

d. Turn the power off, remove ZM-16/U, and re-

nominal value (5.2 to 5.6 amperes).

place link between terminals 1 and 2.

e. Lack potentiometer R69 with Gyptol.

j. Set power supply POWER switch S1 to off. Re-

move load and reinstall A3Q16.

f. Apply input power and set VOLT ADJ coarse and

fine control potentiometers maximum counterclock-

Change 1