GENERAL RADIO COMPANY 1233-A User manual

·""

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./,

.....

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OPERATING

INSTRUCTIONS

··

~

TYPE

1233-A

POWER

AMPLIFIER

GENERAL

RADIO

COMPANY

D

OPERATING INSTRUCTIONS

TYPE

1233-A

POWER

AMPLIFIER

Form

1233-0100-D

November,

1962

GENERAL

RADIO

COMPANY

WEST

CONCORD,

MASSACHUSETTS,

USA

Panel View of the Type 1233-A Power Amplifier

SPECIFICATIONS

INPUT VOLTAGE:

Less

than

0.2

volt

for

full output.

INPUT IMPEDANCE: 100,000

ohms

in

par-

allel:

with

37

pf

(grounded).

POWER SUPPLY: 105 to 125

(or

210 to 250)

volts,

40 to 60

cps;

120

watts

at

zero

output;

140

watts

maximum.

Instrument

will

operate

with

a

maximum

output of

10watts

on

power-supply

frequen-

cies

up

to

400

cycles.

VOLTMETER:

Full

-wave

-

average

type;

150, 50, and 15

volts

f.s.;

Accuracy

±5%,

compensated

to 3 Me.

FREQUENCY RESPONSE: See

plot,

page

8.

PHASE SHIFT: See

plot,

page

8.

Range Switch

Poaitiun

'tOcto'tOkc

'tO

kc

to

1.5

Me

Operating

Freq. Range

'tOe-

'tOke

50c-15

kc

't0kc

-

1.5Mc

't0kc

-

0.5Mc

OUTPUT

Power* Voltage

8 watts

15

watts

8

watts

15

watts

TUBE COMPLEMENT: 2

-6AC7

2

-807

2

-6AG7

1-6]6

TERMINALS: Input

and

output, Type 874

LockingCoaxial

Terminals

with

ground

post

for

double-plug

connection:

Type

938 Binding

Posts

for

balanced

output.

ACCESSORIES SUPPLIED: Two

Type

274-

MB

Double Plugs; two Type 874-C58A

Cable

Connectors;

two

spare

line

fuses,

Type

CAP-22 Power

Cord.

DIMENSIONS: Width 19

3/8,

height

7

1/2

,

depth

15

1/2

'

inches

(495

by

190 by 395

mm)

over-all.

NET WEIGHT:

46

1/2

pounds, (21.5 kg).

U.S.

Patent Nos. 2,548,457; D187,740

Optimum Load

Impedance

600

or

1500

500 grounded

Rise

Ti

me

Distortion

at Rated

01dput

3%

S%

Noise

Level

60

db

below

15

watts, or equiv·

alent to

'tOO

pv

input.

70

db

below

15

watts

or

equivalent

to

63

pv input.

'tOctoSMc

'tOe - S Me

150

volts

, CRO deflec- 0.1 0.6V, peak to peak,

bal,

or

equivalent

to 600 pv peak-

to-peak

input

.

Disconnected

peak-to-peak

lion plates; 1 psec.

bal; 50

volt

~

Mil, 36• leads

grounded

Any single fre-

15

watts, with external tuned

output

transformer

quency,

'tO

c

to

5Mc

•

Rated

output is obtainable

at

105

volts line; output is greater

for

higher line voltages.

OPERATING

INSTRUCTIONS

For

TYPE

1233-A

POWER

AMPLIFIER

SECTION 1.0 DESCRIPTION

1.1

PURPOSE

The Type 1233-A Power Amplifier was designed

for

use

with a

low-level

signal

source

to

provide

a

moderate

amount

of

power

output within

its

fre-

quency

range.

The

circuit

is

arranged

to

provide

maximum

flexibility

for

general

purpose

application.

For

example,

at

one position

of

the output

switch

the Type 1233-A functions

as

a

wide-range

oscilloscope-deflection

amplifier.

A

particular

feature

of the Type 1233-A

is

an

aperiodic

frequency

range

pro-

viding

appreciable

power

output up

to

1.5

Me.

1.2 FREQUENCY RANGE, POWER OUTPUT,

AND

LOAD

IMPEDANCE

The

Type

1233-A

Power

Amplifier

is

arranged

to

operate

over

three

frequency

ranges

as

selected

by

the

output

switch.

1.21

20

Cycles

to

20

Kilocycles

Range:

The

rated

power

output

from

50

cycles

to

15

kilocycles

is

15

watts.

The

output

is

available

for

balanced

or

grounded,

600-

or

150-ohm

loads,

as

selected

by

the

output

switch.

At

20

cycles

and

20

kilocycles

the

rated

power

output

drops

to

8

watts.

1.22

20

Kilocycles to 1.5 Me Range: The

rated

power output

from

20

kilo-

cycles

to

0.5 Me

is

15

watts

into a 50-ohm load, dropping

to

8

watts

at

1.5

Me.

1.23

20

Cycles

to 3 Me Range:

This

output

is

balanced

to

ground

and

up

to

150 volts peak to peak

is

available with a high-impedance load.

The

voltage

gain

is

approximately

60

db.

1.3 INPUT VOLTAGE

AND

IMPEDANCE

Less

than

0.2

volt

at

the input

is

required

to

produce

full

output.

The

input

impedance

is

equivalent

to

100,000

ohms

in

parallel

with

37JJ.JJ.f.

c

<

c

GENERAL

RADIO

COMPANY

1.4 OUTPUT VOLTMETER

The

output

voltmeter

indicates

terminal

voltage and

is

provided with

full-scale

ranges

of 150,

50

and 15

volts.

The

meter

can

also

be switched

to indicate the

plate

current

of

the output

amplifier

tubes.

SECTION 2.0 OPERATION

2.1 CONTROLS

The

controls

consist

of the following: OFF-ON switch with pilot light,

an

OUTPUT

range

selector

and a METER

RANGE

switch.

2.2 TERMINALS

Type 874 Coaxial Connectors

are

provided

at

the INPUT and OUTPUT.

Ground binding

posts

at

3/4-inch

spacing with

the

center

conductor of

these

connectors

permit

connection

to

be

made

also

by

means

of Type 274-MB

Double Plugs if desired. Two insulated binding

posts

are

provided

at

the

out-

put, which

are

used when

BALANCED

output

is

selected. The 115v/230v, 40-60

cycle line

cord

receptacle

is

on the back of the

instrument.

2.3 FUSES

The

line

fuses

are

on the back of the

instrument.

Two-ampere

Slow-

Blow type

are

used

for

115-volt operation.

One-ampere

Slow-Blow type

are

used for 230-volt operation.

2.4 INSTALLATION

The panel

is

designed

for

mounting in a 19-inch

relay

rack, but

remov-

able end

frames

are

supplied

so

that the

instrument

can

be

used

equally well

on

a table.

In

either

case

ventilation should not be appreciably

restricted

or

overheating

may

result.

If

possible

the

space

immediately

above the Type

1233-A should be kept

free

of

other

instruments,

and any

instruments

below

should not produce

large

amounts of heat.

2.5 OPERATION

The

essential

operating information

is

contained in the engraving of the

OUTPUT

range

selector.

2.51

~:

Less

than 0.2 volts

are

required

at

the INPUT to produce full

output in

all

cases.

2.52 Load

Resistance:

For

proper

operation

the load should

match

the

value engraved

at

the

desired

setting of the range

selector

.

For

loads

differ-

ing in value

from

those

provided

an

external

matching

transformer

may

be

used

if maximum output

is

desired

with low

distortion.

2

TYPE

1233-A POWER AMPLIFIER

2.53 Output:

To

keep

distortion

low the output voltage should

be

limited

to

a value

representing

rated

power output into the indicated load

resistance.

R-M-S

POWER LOAD RESISTANCE VOLTAGE

watts ohms

15

600

95

15

150

47.5

15

50

27.4

8

600

69.3

8

150

34,6

8

50

20.0

On the 20c to 3

Me

BAL

HIGH

impedance range the

terminal-to-terminal

peak -

to-peak voltage should

be

limited to

150

volts. This range

is

intended

primarily

for

cathode-ray-oscilloscope

deflection

use.

The

frequency

compensation

of

this

range

has

been

adjusted

so

that

the

transient

response

shows negligible

overshoot when the balanced output

is

connected

directly

to

the deflection

plate

terminals

of a

standard

cathode-ray

oscillograph

with

36-inch

leads.

The

effective

input

resistance

of

each

terminal

to

ground

should

be

at

least

1

megohm

to

prevent

reduction

of

low-frequency

response

,

For

BALANCED

output insulated binding posts

are

used.

In

the

20

cycles

to

3

Me

range

grounded

output

can

be obtained by connecting between one

of

the

insulated

binding

posts

and

the

ground

post, but

the

distortion

will

be

considerably

higher

than

with

balanced output, and the voltage should be

limited

to

50

volts peak

to

peak. In

the

20

cycles

to

20

kilocycles

range

the

BALANCED output

is

actually

an

un-

grounded output, and any

desired

load impedance

relationship

with

respect

to

ground

may

be used.

2.54

Meter:

For

the

20

cycles to

20

kilocycles, and

20

kilocycles

to

1.5 Me

ranges

the voltmeter

circuit

is

switched

to

the

proper

output

terminals

by

the

range

selector.

The

voltmeter

range

is

independently

selected

by

the

METER

RANGE

switch,

On

the

20

cycles to 3

Me

range the voltmeter

circuit

is

switched

to

the

unused

grounded output

terminals

making

the

meter

available

for

ex-

ternal

use.

The

input impedance

of

this

meter

circuit

is

about 15,000

ohms

,

If

desired

and

if

the

loading

effect

of the

voltmeter

can

be

tolerated,

an

ex-

ternal

jumper

can

be

used

to

connect

it

to

either

of

the

insulated

output

ter-

minals

for

the

20

cycles

to 3 Me

range

,

The

meter

can

also

be

switched

by

means

of

the METER

RANGE

switch to indicate the plate

current

of the output

amplifier

tubes.

The

zero

signal

plate

current

is

approximately

80

milli-

amperes

increasing

to

a full

signal

value of approximately 120

milliamperes.

2.55 Line Supply Voltage:

The

power

transformer

is

designed

for

either

115-

or

230-volt

operation

at

40

to

60

cycles.

The

instrument

is

normally

supplied connected

for

115-volt operation in which

case

transformer

terminals

No. 1

and

No. 3

are

connected

together,

and

No. 2 and No. 4

are

connected

together by jumpers.

For

230-volt operation

these

jumpers

must

be

removed,

and No. 2 and

No.3

connected together.

The

fuses

for

230-volt

operation

are

1

ampere

Slow-Blow instead of the 2

ampere

Slow-Blow

fuses

used

for

115-volt

operation.

3

GENERAL RADIO COMPANY

2.56 Caution: High voltage

is

exposed when the

dust

cover

is

removed.

2.6 SPECIAL APPLICATIONS

The available power output

drops

rapidly above 1.5 Me on the

20

kilo-

cycles

to 1.5 Me range. However, full output can be obtained

at

any

particular

frequency up to 5 Me by

connecti~

a

suitable

external

tuned

circuit

in

place

of

the output transformer. This can easily be accomplished by simply removing

the

plate

connectors

on

the Type 807 tubes, substituting leads, to the

external

circuit,

equipped with

similar

plate

connectors;

and attaching a

lead

to high

voltage

plate

supply

(terminals

#5 and

16

on the

small

toroidal

transformer,

T-3),

from the

center

tap

of

the external tuning inductor. The

"special

output

circuit"

diagram

shows the

arrangement

schematically.

The load presented to the output tubes should be

6000

ohms plate-to-plate.

The tuning

capacitor

should be

rated

at

1500 volts

test.

'J,'he

reactance

of the

inductance and tuning capacitor should be about 600 ohms

at

the operating

fre-

quency.

Proper

matching

of

any reasonably low load resistance can be

experi-

mentally obtained by adjusting the number

of

turns

and/

or

the coupling of the

output coil.

Caution: Precautions must be taken to avoid contact with the high voltage

on

the

capacitor

and inductor.

Protection

from

high voltage

inside

the Type

1233-A can be obtained by passing the

necessary

leads to the

external

circuit

through

the

perforations

in

the

dust

cover

.

The

external

circuit

should be

suitably enclosed.

V6

PLATE

___

.__

_____

6000.(1

c

B+(T

3,#5,6)

CENTER

TAP

Special Output

Circuit

4

OUTPUT

COIL

LOAD

TYPE

1233 -A POWER

AMPLIFIER

SECTION 3.0 PRINCIPLES

OF

OPERATION

3.1 ELEMENTARY CffiCUIT

The

elementary

schematic

diagram

illustrates

the

functional

details

of

the

amplifier.

There

are

three

stages

of

push-pull

amplification.

Wide-

band coupling

networks

are

used

between

stages

producing a

flat

response

to

5 Me.

The

input

stage

functions

as

a

phase

splitter

by

virtue

of

an

essentially

infinite

common

cathode

resistor.

Three

possible

output

systems

following

the

last

stage

of

amplification

are

selected

by the output switch, Two

of

these

are

transformer-coupled

and

furnish

power

output.

The

third

permits

the

amplifier

to

function

as

a

wide-band

voltage

amplifier

with

push-pull

output,

the

overall

response

extending to 3 Me.

In

the

20

cycles

to

20

kilocycles

range

the

output

is

available

either

grounded

or

ungrounded and

for

either

150-

or

600-ohm loads

as

selected

by the output switch.

The

output

voltmeter

uses

a

full-wave

bridge

circuit

and

operates

as

an

"average"

type

voltmeter

up

to

5

Me.

The

voltmeter

is

connected

across

the

output

terminals

for

the

two

transformer-coupled

ranges

and

is

switched to the then unused

grwnded

output

terminals

for

the

20

cycles

to

3 Me

range.

3.2 CffiCUIT

The

wiring

diagram

shows

the

complete

circuit

of the

instrument

,

3.21 Power Supply: The power supply

consists

of

a

plate

supply

delivering

250

milliamperes

at

400

volts

using

silicon

rectifiers

in a full-wave

voltage-

doubler

circuit,

a

bias

supply

delivering

30

milliamperes

at

100

volts

using

silicon

rectifiers

in

a

"center-tapped"

circuit,

and two

a-c

heater

supplies.

L-1

is

a

peak

current

limiting

choke

in

the

voltage-doubler

supply. A

two-

section

LC

filter

is

used

in

the

plate

supply. An

RC

filter

is

used

in

the

bias

supply. V-7

is

a

screen

grid

voltage

regulator

for

V-5 and V-6.

Its

function

is

to

maintain

a

relatively

constant

screen

voltage with the

large

screen

current

variation

that

occurs

in

the

output

stage.

Actually

this

circuit

is

just

a d

-c

"cathode

follower"

,

The

grid

voltage

is

obtained

from

the

plate

supply via

the voltage divider R-44, R-45. R-42 and R-43

are

v-h-f

parasitic

oscillation

suppressors.

R-52

is

an

adjustment

for

minimizing

hum due

to

the

heater

supply.

3.22

Input

Amplifier:

V-1

and

V-2

are

the

input

amplifier

tubes.

This

stage

functions

as

a

phase

splitter

providing push-pull output with a

grounded

source

, The common cathode

resistor,

R-3

and

R-4

in

parallel,

is

returned

to

the

100-volt

negative

bias

supply which

permits

a

relatively

high

resistance

to

be

used.

Since

this

resistance

is

large

compared

to the dynamic

resistance

looking back into

the

cathodes

of V-1 and V-2, the

circuit

functions

as

though

no cathode

resistor

were

present,

and

the

input signal divides equally

between

V-1 and V-2, The

result

is

essentially equivalent to applying a push

-pull

signal

grid-to-grid

of

this

stage.

An unbypassed

screen

grid

dropping

resistor

aids

5

GENERAL RADIO COMPANY

maintaining

a

balanced

output.

R-2

,

R-5

,

R-6

and

R-7

are

v-h-f

parasitic

oscillation

suppressors.

L-8

and L-9

are

series-peaking

video-coupling

coils.

3.23

Driver

Amplifier:

V-3 and V-4

are

the

driver

amplifier

tubes.

This

stage

in addition to supplying gain

must

supply sufficient

undistorted

voltage to

the

grids

of

the output

amplifier

to produce full power output.

For

this

reason

and

since

the wide-frequency

range

dictates

relatively

small

plate

load

resis-

tors,

larger

tubes

are

used

here

than

in

the input

stage.

Unbypassed cathode

and

screen

grid

dropping

resistors

help

maintain

balanced

push-pull

output

from

this

stage.

The

potentiometer

R-19

permits

balancing the

signal

voltage

on the

grids

of

the output amplifier. R-14 and R-15

are

v-h-f

parasitic

oscilla-

tion

suppressors.

L-6

and

L-7

are

series-peaking

video coupling

coils.

The

potentiometer

R-54

permits

balancing the

d-e

plate-currents

of

driver-ampli-

fier

tubes,

by applying

differential

grid

bias

to

these

tubes.

3.24 Output

Amplifier:

V

-5

and V

-6

are

the

output

amplifier

tubes

.

This

push-pull

stage

supplies

power output by

means

of

the

low-frequency

trans-

former

T

-2

or

the

high-frequency

transformer

T -3.

It

also

can

be

switched

to

supply push-pull voltage output by

means

of a

series-peaked

video network,

R-29,

R-30,

C-9,

C-10,

L-4,

R-57, and

L-5,

R-58.

R-57

and

R-58

are

used

to

produce

a

gradual

roll-off

of

the

high

frequency

response

in

the

interest

of

good

transient

response. Without

these

resistors

the

response

would

be

essen-

tially

flat

to

5

Me

but

the

transient

response

would show about

10

%

overshoot

with

little

improvement

in

rise

time.

Fixed

bias

is

used

in

this

stage

and

is

obtained by

means

of a voltage dividing network

from

the 100-volt

bias

supply.

Each

tube

has

an

independent

grid

bias

adjusting

potentiometer.

R-23

is

the

grid

bias

potentiometer

for

V-5;

R-24

is

the

grid

bias

potentiometer

for

V-6.

R-27

and

R-28

are

v-h-f

parasitic

oscillation

suppressors.

3.25

Voltmeter

Circuit:

D-1

and

D-2

are

crystal

diodes

used

in

the

volt-

meter

circuit.

A

form

of

bridge

circuit

is

used

which functions

as

a

full-wave

"average''

voltmeter

up to 5 Me. Range switching

is

accomplished

in

the

d-e

meter

circuit.

The

rheostats

R-34,

R-36

, and R-38

are

the

calibrating

adjust-

ments

for

the

15-,

50-,

and

150-volt

ranges

respectively.

For

plate

current

metering

R-39

and

R-40

provide

a

full-scale

meter

sensitivity

of 150

milli-

amperes.

SECTION 4.0 CALIBRATION

AND

ADJUSTMENT

There

are

seven

screw-driver

adjustments

provided

in

the

instrument.

These

adjustments

are

initially

made

at

the

factory

and

should

not

require

adjustment

in

the

field

unless

tubes

and/

or

components

are

replaced.

The

function

of

each

one ot

the

adjustments

has

been

described

in

Principles

of

Operation.

If

it

is

desired

to

follow through the complete adjustment

procedure,

it

is

recommended

that

it

be

done

in

the

order

given and

after

the

instrument

has

been

operating

for

a

sufficient

time

to

become

thoroughly

warmed

up.

4.1

R-23,

R-24

Function: output

amplifier

bias

adjustments.

Location:

front

of

chassis

-

beside

807

tubes

-

accessible

from

top.

OUTPUT

switch:

20

cycles

to

20

kilocycles

range.

6

TYPE

1233-A POWER AMPLIFIER

INPUT:

shorted.

Insert

a

milliammeter

between

plate

cap

and

V-5

(see

note).

Adjust

R-23

for

40

milliamperes

plate

current.

Remove

milliammeter

and

replace

plate

cap

on V-5

(see

note).

Insert

milliammeter

between

plate

cap

and V-6

(see

note).

Adjust

R -24

for

40

milliamperes

plate

current.

Remove

milliammeter

and

replace

plate

cap

on V-6

(see

note).

Repeat

above

as

there

may

be

a

slight

interaction

of

the

adjustments.

CAUTION: Line

switch

must

be

turned

off while

plate

connection

is

opened

or

damage

may

result

to

tubes.

4.2

R-54

Function:

driver

amplifier

d-e

balancing

adjustment.

Location: top of

chassis

between

tubes

and

electrolytic

capacitors.

Set

R-19

so

that

there

is

same

plate

load

resistance

for

V-3 and V-4

as

measured

by

an

ohm

meter

(instrument

power off).

Connect 0 h

10

volt

meter

between the

grid

ends of

L-6

and

L-7.

Turn

instrument

on and allow

it

to

warm

up. Adjust

R-54

for

zero

indication

on

the

voltmeter.

INPUT:

shorted.

4.3

R-19

Function: output

amplifier

grid

signal

balancing

adjustment.

Location:

front

of

chassis

-between 807

tubes

-

accessible

from

top.

OUTPUT switch:

20

cycles

to

20

kilocycles

-600

ohms

-grounded.

Load: 600

ohms.

INPUT: 1

kilocycle

low

distortion

-

adjust

level

to

produce

95

volts

output, Connect a

distortion

meter

across

the output using

an

external

voltage

divider

if

necessary

to

bring

the

voltage

level

within

its

range

(see

note),

Adjust

R-19

for

minimum

distortion.

NOTE: A wave

analyzer

may be

used

if

desired,

in

which

case

it

should

be

tuned

to

the

second

harmonic.

4.4

R-52

Function: hum

adjustment.

Location: top of

chassis

-

center

left

-

accessible

from

top.

OUTPUT

switch:

20

cycles

to

20

kilocycles

-600

ohms

-grounded.

Load: 600

ohms.

INPUT:

shorted.

Connect a

noise

meter

across

output

(see

note).

Adjust

R-52

for

minimum

noise.

NOTE: Awave

analyzer

may be

used

if

desired,

in which

case

it

should

be tuned

to

the

line

frequency.

7

GENERAL RADIO COMPANY 1233-A User manual

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