Power Supply 1A1 Circuit Functioning-continued

TM 11-5820-695-35

current through CR8. The base voltage for Q9 is

below the output voltage; the transistor is turned off

When the output voltage rises above the regulated

derived from the voltage divider consisting of R12, R13

and R14. When the voltage regulator is configured to

level, the base of Q9 becomes negative with respect to

its emitter and the transistor conducts. This gates on

operate at 5 volts, resistor R14 is short circuited by

silicon-controlled rectifier Q1 and short circuits the

connecting pin 9 to the negative output lead pin 8.

rectifier output voltage. The short circuit current is

When the output is in regulation, the voltage at the base

limited by the transformer winding resistance.

of Q9 is approximately 3.0 volts below the regulator

output voltage. The emitter is clamped at 3.3 volts

Change 6

2-55