BATTERY CHARGER FUNCTION.

TM 11-6625-2976-40

1-18. VAR LAMP FLASHER CAPABILITY. (CONT)

Positive potentials applied through the 30 REF and 30 VAR switches hold C2 and C4 paths of U18

closed. Pressing lamp switch S25 transfers the positive potential from U18 C3 to Cl, thereby changing

the signal path to place VOR variable R3 in the circuit.

At the same time, S25 applies +8 v through the lamp to the lamp flasher circuit at CR6. The initial

application of positive voltage through the lamp causes the conduction of Q6 to decrease, allowing

C37 to charge and causing the negative input to U33A to change to a negative direction. The output of

U33A changes to a positive direction, causing Q7 to conduct. Q7, in turn, lights the lamp and causes

the input of Q6 to become more negative. Q6 conducts harder, discharging C37 and causing the U33A

input to become more positive. As a result, Q7 turns off, Q6 conduction decreases, and C37 again

begins to charge. The cycle repeats itself, periodically blinking the lamp, as long as S25 remains

depressed.

1-19. BATTERY CHARGER FUNCTION.

Refer to FO-8 while reading the text In this section.

The battery charger is wired for 115 vac operation, However, 230 vac operation is possible by rewiring

the transformer. Instructions for rewiring the transformer are provided in paragraph 2-34.

The battery charger accepts input voltage from plug PI through 0.5 amp fuse F1.

if test set is wired for 230 vac operation, F1 is a 0.25 amp fuse.

Lamp DS1 lights to indicate that the battery charger has power applied,

The battery charger converts ac power to + 8 vdc and -8 vdc by utilizing a transformer T1, half-wave

rectifiers CR1 and CR2, RC filters, and voltage regulating zener diodes.

Ac power from P1 is applied through fuse F1 and transformer T1 to half-wave rectifiers CR1 and CR2.

CR1 cuts off the negative half of the input sine wave and passes the positive half to RC filter Cl and R1.

Cl charges during conduction of the positive part of the wave and discharges through R1 during the

clipping of the negative part of the wave.

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