POWER SUPPLY

T.O. 31W2-2GSC24-2

TM 11-5805-688-14-1

NAVELEX 0967-LP-545-3010

power supply by shutting down the power supply when

5-620. POWER SUPPLY.

the ac source voltage decreases to 80 vac or less.

When the incoming voltage decreases to 80 vac or less,

5-621. GENERAL.

In the power supply, electrical

an inhibit signal is generated to inhibit the +5volt power

components are mounted directly on the power supply

supply. Turning off the +5-volt power supply completely

chassis, on the motherboard (A1), and on four plug-in

cards. The four plug-in cards, 12volt regulator card A1,

shuts down the power supply. When the input ac voltage

increases to 100 vac or more, the inhibit signal is

+5-volt regulator card A2, 12-volt driver card A3, and

removed and the power supply becomes functional

+5-volt driver card A4; all plug into the motherboard. The

again. The +5-volt power supply generates the +5V (c)

block diagrams associated with the block diagram

power required to operate the voltage regulator and clock

discussion are shown in figures FO-11, 5-46, and 5-47.

generator circuits.

The following schematic diagrams in the circuit diagrams

manuals are used in the detailed circuit discussions:

5-626. The +5-volt and 12-volt over/under voltage

power supply, 12-volt regulator card, +5-volt regulator

detectors (figure 5-46) monitor the +5V Reg, +12V Reg,

card, 12-volt driver card, and the +5-volt driver card.

and -12V Reg outputs from the power supply and

automatically shuts down the power supply when an

5-622. BLOCK DIAGRAM DISCUSSION.

over-voltage condition occurs. When an over-voltage

condition occurs, the appropriate detector circuit

5-623. The 115 vac input is applied to step-down

produces a signal through CR2, CR4, or CR6 that

transformer T6 and to the +150-volt power supply (figure

causes the clock error control circuit to generate an

FO-11). The +150-volt unregulated output from the

inhibit signal to the clock generator. At the same time, a

+150-volt power supply is the source voltage for the five

signal is also applied through CR1, CR3, or CR5 that

sets of switches in the outputs of the regulated power

causes the alarm generator circuit to generate a signal

supplies. Step-down transformer T6 produces a 18.5-

that, in turn, causes a drivers circuit to produce the local

vdc output that is applied to the +12-volt and -12-volt

alarm and remote alarm signals. The local alarm signal

power supplies. In turn, the two power supplies generate

lights the POWER SUPPLY ALARMS indicator on the

the +12V (c) and -12V (c) voltages that power the control

front panel. The remote alarm signal is applied to the

and voltage regulator circuits.

ERD card to initiate a power supply failure remote alarm

signal. The clock generator circuit contains a 18-kHz

5-624. The constant current generator provides a

oscillator that produces 18-kHz pulses through switch Q4

constant current source of 7.5 ma to the reference

and two inverters to the B clock and A clock flip-flops.

voltage generator. The reference voltage generator, in

The B clock flip-flop produces 9-kHz B clock pulses

turn, produces a constant +4.77V reference (Ref) voltage

through an inverter to the five voltage regulator circuits.

that is applied to the clock generator, 12-volt regulator

In turn, the A clock flip-flop produces similar A-clock

circuit, +5-volt regulator circuits (4), and the +5 and 12-

pulses to the five voltage regulator circuits. The A clock

volt over/under voltage detectors.

and B clock pulses are shut down when an inhibit signal

from the clock error control circuit is applied to switch

5-625. The 4.77 Ref and +12V (c) voltages are applied

Q4.

to the low-voltage detector circuit. The low-voltage

detector circuit provides low-voltage protection for the

Change 2 5-169