TM 11-5820-765-34
VOLTAGE SURGE PROTECTOR DIODE CR6:
Connected across transformer's power secondary winding.
Protects voltage regulator rectifier SCR1 (Q1) and bridge rectifier diodes CR1-CR4 from
transient voltage spikes.
V O L T A G E REGULATION CIRCUIT
Built into circuit card assembly PC101 (A1).
Controls firing time of silicon controlled rectifier SCR1 (Q1).
Keeps dc voltage at adjusted setting.
EXPLANATION:
SCR1 (Q1) fires twice each cycle of ac input voltage. By controlling firing time, SCR1 (Q1)
can be varied from full on when fired at start of each half-cycle to full off when fired
at end of half-cycle.
Bridge rectifier's dc output voltage can thus be varied from maximum possible voltage to
zero.
OVERVOLTAGE
CIRCUIT
CIRCUIT PARTS:
Silicon controlled rectifier SCR2 (Q2).
Low-resistance resistor R3.
Protects equipment being powered from overvoltages.
Activated when malfunction causes rise in output voltage.
ACTION:
C i r c u i t r y in PC101 (A1) senses trouble, fires SCR2 (Q2).
RESULTS:
Firing applies short-circuit load to output terminals which reduces output voltage to very
low value.
Short-circuit load opens circuit breaker CB1, which turns power supply OFF.
This prevents possible damage to power supply and equipment being pawered.
VOLTAGE ADJUST CIRCUIT (DC OUTPUT)
CIRCUIT PARTS:
Variable dc voltage adjust resistors R4, R8.
Stabilizing
capacitor
C3.
Fixed
resistor
R11.
CONNECTION:
Do output voltage fed through resistors to PC101(A1).
VOLTAGE
PATH:
Do
output
negative
()
terminal
to
PC101
(A1).
Adjusts power supply's dc output voltage.
Activated when dc output voltage changes.
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