Continental Electronics 816R - Primary Power Distribution and Overload Circuits; Power Distribution and Turn-On; FWD;REFL & Auto Power Control

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3.

PRIMARY

POWER

DISTRIBUTION

CONTROL

AND

OVERLOAD

CIRCUITS

Primary

Power

Distribution.

The

60

Hz,

3-phase

primary

power

is

distributed

to

the

various

circuits

of

the

transmitter

via

circuit

breakers

and

fuses

mounted

on

circuit

breaker

panel

A6.

Circuit

breaker

A6CB5

is

connected

inside

the

delta

of

plate

transformer

Tl.

It

also

serves

to

interrupt

primary

power

to

the

PA

screen

transformer

T2

through

associated

circuit

breaker

A6CB4.

Circuit

breaker

A6CB3

controls

power

to

driver

power

supply

(IPA)

transformer

T5.

AC

line

voltage

metering

is

provided

by

ac

meter

A2M1.

In

addition

to

the

three

phase-to-phase

voltages,

a

fourth

position

of

switch

A2S1

is

used

to

monitor

the

power

amplifier

filament

voltage.

BLOWERS

circuit

breaker

A6CB2

controls

application

of

primary

power

to

cavity

blower

Bl

and

FAN

fuses

A6F7,

F9,

and

F12

through

filament-on

relay

A8K2.

Relay

A8K2

is

energized

when

the

filament

switch

(S2)

is

turned

on.

Application

of

primary

power

to

the

filament

circuits,

the

exciter,

the

power

amplifier

bias

power

supply,

and

the

power

amplifier

tuning

and

loading

motors

is

relay

controlled.

Filament-on

relay

A8K1

and

blower-on

relay

A8K2

control

application

of

power

to

the

regulated

filament

circuit

through

auto-transformer

A8A2T1.

Relay

A8K1

also

controls

application

of

power

to

802B

exciter

A4,

to

power

amplifier

bias

power

supply,

P/O

A10,

and

to

the

power

amplifier

tuning

and

loading

motors

B2

and

B3

respectively.

Power

to

the

exciter

and

the

motors

is

through

isolation

transformer

T4.

Time

totalizing

meter

A2M2

is

placed

across

the

load

side

of

filament-on

relay

A8K1.

The

filament,

exciter,

and

power

amplifier

bias

supply

input

power

circuits

are

protected

by

associated

fuses.

These

circuits

receive

power

from

the

blowers

circuit

breaker,

A6CB2.

Transmitter

Turn-On.

The

transmitter

is

energized

by

pressing

FILAMENT

ON

switch

A1S2

on

the

Al

control

panel.

Relay

A8K2

is

energized

and

is

applied

to

the

blower

motors.

After

sufficient

air

pressure

is

created

in

the

power

amplifier

cabinet,

air

switch

A12S1

is

closed

and

relay

A8K1

is

energized.

After

a

30-second

delay,

relay

A8K4

is

energized.

The

PLATE

ON

switch

is

pressed

energizing

relay

A8K3

which

applies

28

V

de

to

the

base

of

transistor

A2A6Q3.

This

turns

on

the

control

amplifier,

which

applies

input

voltage

to

the

plate

and

power

supplies.

The

transmitter

may

also

be

energized

by

pressing

the

PLATE

ON

switch

which

latches

relay

A8K3,

and

energizes

relay

A8K2

through

contacts

8

and

5.

Pressing

this

single

switch

(PLATE

ON)

enables

the

transmitter

to

go

through

the

above

sequence

of

blower,

filament,

time

delay

and

plate

on.

An

output

override

voltage

is

supplied

to

the

802B

exciter

when

the

plate

voltage

is

turned

OFF.

This

mutes

the

output

of

the

exciter

while

the

power

amplifier

plate

voltage

is

turned

OFF

(Figure

7).

The

voltage

is

applied

from

the

28

V

de

power

supply

through

contacts

3

and

9

of

relay

A8K4

to

the

802B

exciter

power

supply

regulator.

FWD/REFL

Calibrate

and

Auto

Power

Control

Unit,

A2A6.

Functions

.

The

FWD/REFL

CALIBRATE

AND

AUTO

POWER

CONTROL

portion

of

the

A2A6

card

performs

these

functions

(Refer

to

Schematic

180162):

1.

The

forward

power

signal

from

the

directional

coupler

is

buffered

and

amplified

to

provide

a

panel

power

meter

reading

of

100%

at

the

customer

’

s

specified

transmitter

power

output

(TPO).

Full

scale

meter

indication

is

120%

in

the

FORWARD

POWER

position.

2.

The

forward

power

signal

from

the

directional

coupler

is

compared

against

either

of

two

internal,

adjustable

voltages

for

automatic

power

control.

Two

discrete

levels

of

power

control

are

remotely

selectable

and

maintain

the

desired

power

to

within

1

%.

3.

The

reflected

power

signal

from

the

directional

coupler

is

buffered

and

amplified

to

provide

a

full

scale

reading

of

12%

of

the

customer

’

s

specified

TPO

on

the

panel

power

meter

in

the

REFLECTED

POWER

position.

13