TM 11-5820-765-34
1-11. POWER AND VOLTAGE CIRCUITS
P O W E R CIRCUITS
PP-4763
CIRCUIT BREAKER CB1 (refer to FO-2):
Single
ac
power
switch.
Turns power supply ON, OFF.
Protects against overloading power
supply.
Power ON: Connects 115-volt ac source to primary winding, power transformer T-1,
and to fan motor B1.
PP-4763A
CIRCUIT BREAKER CB1 (refer to FO-3):
Dual ac power switch.
Turns power supply ON, OFF.
In series with both legs of ac input power.
Power ON: Connects either 115-or 230-volt ac source to primary winding, power
transformer T1, and to fan motor B1.
SAFETY INTERLOCK SWITCH S1:
Opens input power circuit when unit's top panel is removed.
This is a protective control.
Functional Analysis of Power Circuit Parts
TRANSFORMER T1:
Secondary
winding:
Power secondary supplies full-wave bridge
rectifier
( r e c t i f i e r diodes CR1, CR2, CR3, and CR4).
Two control secondaries supply circuit card assembly PC101 (Al).
SILICON CONTROLLED RECTIFIER SCR1 (Q1):
Connected
in
bridge
rectifier
outlet.
Regulates
dc
output.
REACTOR L2:
Connected
in
ac
supply
to
bridge
rectifier.
Introduces
time delay needed
to operate SCR1
(Q1).
DIODE CR5:
Connected
across
bridge
rectifier's
output.
Provides discharge path for filter reactor L1.
Prevents
continued
firing
of
SCR1
(Q1).
BLEEDER RESISTORS R1, R10:
Connected
across
bridge
rectifier's
output.
Stabilize
power
supply's
operations
during
low-load
conditions.
PP-4763A includes choke L3 in series with R10.
