HP 200AB Owner's manual

OPERATING

AND

SERVICING

MANUAL

MODEL

200AB/ABR

AUDIO

OSCILLATOR

SERIALS

PREFIXED:

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AMPLITUDE

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Copyright

HEWLETT-PACKARD

COMPANY

1955

1501

PAGE

MILL

ROAD,

PALO

ALTO,

CALIFORNIA,

U.S.A.

FREQUENCY

RANGE:

BANDS:

CALIBRATION

ACCURACY:

FREQUENCY

DIAL:

FREQUENCY

RESPONSE:

FREQUENCY

STABILITY:

gol

DISTORTION:

INTERNAL

IMPEDANCE:

HUM

AND

NOSE:

POWER

SUPPLY:

DIMENSIONS:

WEIGHT:

(

POWER

OUTPUT:

SPECIFICATIONS

20

cps

to

40

kc.

x1

20

cps

to

200

cps

X10

200

cps

to

2

ke

X100

2ke

to

20

kc

200

4kce

to

40

kc

+2%

including

calibration

error,

warm-up,

and

changes

due

to

aging

of

tubes

and

components.

Six

inch

diameter,

calibrated

over

300°

of

arc.

72

divisions.

Total

scale

length,

63

inches.

Vernier

control

for

precise

setting.

+1

db

entire

frequency

range

when

working

into

rated

load

(reference

1

kc).

Line

voltage

variations

of

+10%

cause

negligible

shift

in

output

frequency.

1

watt

or

24.5

volts

into

a

600

ohm

load.

Less

than

1%,

20

cps

to

20

kc;

less

than

2%,

20

kc

to

40

kc

when

ne

4

into

pate

load

or

nigper

impedance.

O.i5SKZ

@

400Hz

+Sdbm

/74

Approximately

75

ohms

from

20

cps

to

20

kc.

Output

is

balanced

to

ground

over

entire

frequency

range

(may

be

operated

one

side

grounded,

if

desired).

At

least

66

db

below

rated

output

(less

than

0.05%

of

rated

output).

115/230

volts,

50/1000

cps,

70

watts.

Cabinet:

7-3/8"

wide,

11-1/2"

high,

12"

deep.

Rack:

19"

wide,

7"

high,

11"

deep

behind

panel.

Cabinet:

15

lbs.,

Rack:

19

lbs.,

shipping

20

lbs.

shipping

30

lbs.

Section

I

Section

II

Section

ITI

Section

IV

Section

V

TABLE

OF

CONTENTS

FOR

MODEL

200AB

AUDIO

OSCILLATOR

GENERAL

DESCRIPTION

a

General

.

2

Inspection

.

o-

Bnc8

-3

Power

Source

Voltage

4

Power

Cable

.

$

OFERATING

INSTRUCTIONS

1

Controls

and

Terminals

.

-2

Operation

of

the

Instrument

CIRCUIT

DESCRIPTION

3-1

General

.

MAINTENANCE

4-1

Removal

of

Case

.

4-2

Tube

Replacement

BN

nea

See

4-3

Replacement

of

Electrolytic

Capacitors

.

4-4

Replacement

of

Lamp

R11

.

4-5

4-6

4-7

230

Volt

Power

Transformer

Conversion

.

Trouble

Shooting

.

TABLE

OF

REPLACEABLE

PARTS

5-1

Table

of

Replaceable

Parts

Lubrication

of

the

Tuning

Capacitor

Drive

Mechanism

Page

I-1

II-1

II

-

1

Hil

- 1

<deedaa

1-1

GENERAL

The

Model

200AB

Audio

Oscillator

is

designed

for

general

purpose

audio

testing

and

measurements.

The

resistance-capacity

oscillator

used

in

this

in-

strument

will

retain

its

high

degree

of

accuracy

for

long

periods

of

time

with

no

adjustment.

The

push-

pull

output

amplifier

used

in

the

Model

200AB

has

a

large

amount

of

overall

negative

feedback

for

maxi-

mum

stability

and

low

distortion.

The

output

impe-

dance

of

the

instrument

is

600

ohms

balanced

or

un-

balanced.

The

output

voltage

is

adjustable

from

0

to

24.5

volts

(1

watt)

across

a

600

ohm

resistive

load

over

the

full

range

of

20

to

40,

000

cycles/second,

and

is

sufficient

for

modulating

signal

generators

or

other

applications

that

require

considerable

power.

1-2

INSPECTION

After

the

instrument

is

unpacked,

it

should

be

care-

fully

checked

for

damage

received

in

transit.

If

any

shipping

damage

is

found,

follow

the

procedure

out-

lined

in

the

Claim

for

Damage

in

Shipment"

section

on

the

last

page

of

this

instruction

book.

a

Sect.I

Page

1

SECTION

|

GENERAL

DESCRIPTION

1-3

POWER

SOURCE

VOLTAGE

The

200AB,

like

other

@instruments,

is

shipped

from

the

factory

with

the

power

transformer

dual

primary

windings

connected

for

operation

froma

115

volt

a-c

source

unless

otherwise

specified

on

the

order.

If

operation

from

a

230

volt

a-c

source

is

desired,

the

transformer

primary

windings

can

be

quickly

reconnected.

Refer

to

Section

IV,

para-

graph

4-6

for

details.

1-4

POWER

CABLE

The

three-conductor

power

cable

supplied

with

this

instrument

is

terminated

in

a

polarized

three-prong

male

connector

recommended

by

the

National

Elec

-

trical

Manufacturers'

Association.

The

third

contact

is

an

offset

round

added

to

a

standard

two-blade

connector

which

grounds

the

instrument

chassis

when

used

with

an

appropriate

receptacle.

To

use

this

connector

with

a

standard

two-contact

receptacle,

an

adapter

should

be

used

to

connect

the

NEMA

con-

nector

to

the

two-contact

system.

When

the

adapter

is

used,

the

third

contact

is

terminated

in

a

short

lead

from

the

adapter

which

can

then

be

connected

to

a

suitable

ground.

2-1

CONTROLS

AND

TERMINALS

ON

This

toggle

switch

controls

the

power

supplied

to

the

instrument

from

the

power

line.

When

the

instrument

is

turned

on,

a

glow

will

be

visible

through

the

plastic

frequency

dial

index.

RANGE

This

rotary

switch

changes

resistance

values

in

the

frequency

determining

sections

of

the

instrument.

The

position

of

this

switch

determines

the

multiplying

factor

that

must

be

used

to

convert

the

frequency

dial

indication

to

the

actual

output

frequency

of

the

instrument.

AMPLITUDE

This

control

is

a

potentiometer

that

is

used

to

vary

the

amount

of

oscillator

voltage

that

is

applied

to

the

amplifier

section

of

the

instrument,

and

thus

deter-

mines

the

amplitude

of

the

output

voltage.

Frequency

Dial

This

control

varies

the

capacity

in

the

frequency

determining

circuits

of

the

instrument,

and

thus

varies

the

output

frequency.

This

dial

is

calibrated

from

20

to

200

and

its

indication

multiplied

by

the

factor

indicated

by

the

RANGE

switch

will

give

the

actual

output

frequency

of

the

oscillator.

The

small

knob

just

below

the

frequency

dial

(on

the

right

hand

side

on

the

rack

model)

is

a

vernier

control

for

this

dial.

600

2,

G

The

output

voltage

of

the

instrument

appears

at

these

terminals.

The

two

right

hand

binding

posts

(marked

600

2)

connect

directly

to

the

output

transformer

of

the

instrument.

This

600

2

output

is

balanced

to

ground,

The

left

hand

binding

post

(marked

G)

is

connected

to

the

chassis

of

the

instrument.

Sect.

II

Page

1

SECTION

Il

OPERATING

INSTRUCTIONS

FUSE

The

fuseholder,

located

on

the

back

of

the

instrument,

contains

a

.8

ampere

slow-blowing

fuse.

For

230

volt

operation

this

fuse

should

have

a

.4

ampere

rating.

2-2.

OPERATION

OF

THE

INSTRUMENT

The

procedure

for

correct

operation

of

the

Model

200AB

is

as

follows:

a.

Connect

the

power

cable

to

a

suitable

power

source,

>.

Turn

the

power

switch

on

and

allow

about

five

minutes

for

the

instrument

to

reach

its

normal

operating

temperature.

c.

Set

the

Frequency

Dial

and

the

RANGE

switch

for

the

desired

operating

frequency.

For

example:

the

desired

output

frequency

is

5000

cycles/sec.,

set

the

Frequency

Dial

to

50

and

the

RANGE

switch

to

X100

(50

x

100

is

5000).

d.

Connect

the

instrument

to

the

equipment

under

test.

A

description

of

the

various

types

of

out-

put

available

from

the

instrument

follows:

1)

600

ohm

balanced

or

unbalanced

output

may

be

obtained

as

follows:

G

600

2

G

600

2

GND

BALANCED

OUTPUT

UNBALANCED

OUTPUT

Sect.IT

Page

2

2)

If

a

generator

with

an

internal

impedance

of

600

ohms

is

desired,

the

Model

200AB

may

be

connected

as

follows:

600

2

600

2

G

GND

270

2

270

Q

GND

BALANCED

OUTPUT

UNBALANCED

OUTPUT

560

2

Under

these

conditions

the

output

voltage

available

to

a

600

ohm

load

will

be

reduced

to

approximately

12

volts

and

the

power

will

be

reduced

to

approxi-

mately

1/4

watt.

CAUTION

To

minimize

distortion

in

the

output

voltage,

the

instrument

should

work

into

a

load

of

600

to

6000

ohms

resistive.

e.

Set

the

AMPLITUDE

controls

so

the

Model

200AB

is

delivering

the

desired

voltage

to

the

equipment

under

test.

If

a

small

output

voltage

with

minimum

noise

is

desired,

best

results

will

be

obtained

by

externally

attenuating

the

instrument

output

rather

than

by

decreasing

the

AMPLITUDE

control.

The

input

to

the

external

attenuator

should

be

approxi-

mately

20

volts

for

the

best

possible

signal

to

noise

ratio.

The

Hewlett-Packard

Model

350B

Attenuator

may

be

used

for

this

purpose

if

the

instrument

is

being

used

to

supply

an

unbalanced

signal.

A

balanced

attenuator

should

be

used

to

attenuate

a

balanced

signal.

A

simple

voltage

divider

will

also

be

suf-

ficient

in

many

cases,

the

total

resistance

of

the

voltage

divider

should

be

approximately

600

ohms.

G

600

Q

G

600

Q

560

Q

270

2

270

Q

56

Q

56

Q

GND

10:1

UNBALANCED

10:1

BALANCED

VOLTAGE

DIVIDER

VOLTAGE

DIVIDER

This

type

of

output

attenuator

is

suitable

when

the

Output

impedance

of

the

instrument

is

not

critical.

—

When

a

low

voltage

is

desired

for

testing

low

im-

pedance

circuits,

it

may

be

obtained

by

first

atten-

uating

the

oscillator

output

with

a

600

ohm

attenuator

and

then

changing

the

impedance

by

means

of

a

transformer

such

as

the

Hewlett-Packard

#912-17

or

a

suitable

resistive

impedance

matching

pad.

The

Hewlett-Packard

line

matching

transformer

will

provide

output

impedances

of

600,

250,

150,

62.5

or

37.5

ohms

from

a

600

ohm

source.

\

|

Careers

ig

pete

oe

3-1

GENERAL

The

circuit

of

the

Model

200AB

consists

of

an

oscil-

lator

section,

a

push-pull

amplifier

section,

and

a

conventional

power

supply.

The

oscillator

section

consists

of

a

6SJ7

(V1)

anda

6K6

(V2)

and

is

basically

a

two

stage

resistance

coupled

amplifier.

Two

feedback

loops

are

used

around

this

amplifier,

positive

feedback

to

set

up

oscillations,

a

negative

feedback

to

reduce

distortion

E

Positive

Feedback

Ou

LAMP

Rit

Negative

Feedback

Figure

3-1.

SE

Sect.1

Page

1

SECTION

Iil

CIRCUIT

DESCRIPTION

and

keep

the

amplitude

of

oscillation

constant.

The

positive

feedback

network

contains

fixed

resistance

values

and

a

variable

capacitor

(see

Figure

3-1)

is

proportioned

such

that

Rj C1

=

Rg

Cg.

The

oscil-

lator

output

voltage

is

applied

to

this

network

and

the

oscillator

input

voltage

is

derived

from

it.

Since

the

input

and

output

signals

of

a

two

stage

amplifier

are

in

phase,

oscillations

will

occur

when

the

phase

shift

between

the

voltage

applied

to

the

network

and

the

voltage

at

the

grid

of

the

first

stage

is

zero.

The

zero

phase

shift

point

is

also

the

point

of

mini-

R1I6

RI

&

R2

Correspond

to

range

resistors

RI-R8

Cl

&

C2

Correspond

to

ci!

thru

c4

Simplified

Oscillator

Circuit

Sect.

III

Page

2

mum

loss

through

the

network

as

indicated

by

the

curves

of

Figure

3-2,

The

frequency

of

oscillation,

RELATIVE

FREQUENCY

=

1

in

Figure

3-1,

is

equal

to

1/2

7

VRj

Cy

Ro

Cg

or

1/2

7

RC

since

R1

=

R2

and

Cj

=

Cg.

The

cathode

by~pass

capacitors

in

the

oscillator

section

(C5,

C7)

are

to

correct

phase

shift

at

the

higher

operating

frequencies

of

the

instrument.

The

negative

feedback

network

in

the

oscillator

section

minimizes

changes

in

oscillator

amplitude

with

changes

in

frequency.

The

incandescent

lamp

is

used

as

a

cathode

bias

resistor,

and

is

also

part

of

the

negative

feedback

voltage

divider

in

the

first

stage

of

the

oscillator

(V1).

The

lamp

has

a

temper-

ature-resistance

characteristic

such

that

its

resis-

tance

will

increase

in

direct

proportion

to

the

voltage

applied

to

it.

Changes

in

the

resistance

of

this

lamp

will

change

the

percentage

of

negative

feedback

in

the

oscillator

circuit.

When

the

oscillator

voltage

rises,

more

voltage

is

applied

to

the

lamp

(R11),

the

increased

voltage

will

raise

the

temperature

and

re-

sistance

of

the

lamp

which

in

turn

increases

the

per-

centage

of

negative

feedback

in

the

oscillator

circuit.

Increasing

the

percentage

of

negative

feedback

will

tend

to

decrease

the

oscillator

output

voltage

to

its

normal

operating

point.

The

action

will

be

reversed

if

the

oscillator

output

voltage

decreases,

the

negative

feedback

voltage

will

decrease

lowering

the

voltage

across

the

lamp

(R11)

which

will

lower

its

resistance

thus

lowering

the

percentage

of

negative

feedback

and

tending

to

raise

the

oscillator

output

to

its

normal

operating

point.

The

thermal

inertia

of

the

lamp

is

great

enough

so

that

its

resistance

will

not

vary

in

accordance

with

the

sine

wave

voltage

at

the

lowest

frequencies

involved.

The

amplifier

section

of

the

instrument

is

a

feed-

back

amplifier

circuit

containing

a

push-pull

output

amplifier.

The

first

amplifier

tube

(V3A)

is

directly

coupled

to

the

phase

inverter

tube

(V3B).

The

phase

inverter

drives

the

output

amplifier

tubes

(V4

and

V5).

The

output

transformer

contains

a

tertiary

winding

for

overall

negative

feedback

in

the

amplifier

section.

The

cathode

bias

resistor

of

the

first

stage

(V3A)

is

not

by-passed

giving

additional

negative

feedback.

This

large

amount

of

negative

feedback

(over

30

db)

in

the

amplifier

section

results

in

very

little

distortion

being

introduced

by

the

amplifier

section

of

the

instrument.

The

power

supply

section

of

the

instrument

consists

of

a

conventional

full

wave

rectifier

with

pi-section

filter.

PHASE

RELATIVE

Figure

3-2.

FREQUENCY

Ratio

Phase

-—--

Positive

Feedback

Network

Characteristics

(i

q

nn

i

RS

om

a

Taek

CAUTION

Sect.IV

Page

1

SECTION

IV

MAINTENANCE

The

trimmers

on

the

main

tuning

capacitor

(C2

and

C4)

affect

both

calibration

and

frequency

response.

The

settings

of

these

two

capacitors

should

not

be

changed

unless

the

instrument

needs

recalibration.

4-1

REMOVAL

OF

CASE

On

the

rear

cover

of

the

instrument

there

are

two

screws

that

hold

the

case

on

the

instrument.

Removal

of

these

screws

will

allow

the

instrument

to

slide

forward

out

of

the

case.

4-2.

TUBE

REPLACEMENT

When

replacing

any

of

the

tubes,

with

the

exception

of

the

rectifier,

distortion

measurements

should

be

made

to

determine

whether

or

not

the

instrument

still

meets

the

specifications

set

forth

in

the

front

of

this

instruction

manual.

Poor

tubes

can

greatly

increase

the

noise

and

distortion

components

of

the

output

waveform.

4-3

REPLACEMENT

OF

ELECTROLYTIC

CAPACITORS

The

electrolytic

capacitors

in

this

instrument

are

very

high

quality

capacitors

with

a

life

of

from

five

to

ten

years,

4-4

REPLACEMENT

OF

LAMP

R11

This

lamp

operates

well

below

its

rating

and

should

have

an

infinite

life.

The

lamp

may

be

damaged

by

severe

mechanical

vibration.

If

the

lamp

is

damaged,

a

notch

may

appear

in

the

output

waveform

and

the

oscillator

voltage

may

be

excessive.

If

the

lamp

opens,

the

circuit

will

not

oscillate.

If

it

is

nec-

essary

to

replace

the

lamp,

the

oscillator

voltage

should

be

checked

to

make

certain

it

falls

within

the

range

specified

on

the

schematic

diagram.

Mea-

sure

this

voltage

between

the

negative

terminal

of

C8

and

chassis

(see

Figure

4-3

for

the

location

of

C8).

Adjust

the

value

of

RIO

until

the

proper

oscil-

lator

output

is

obtained.

4-5

LUBRICATION

OF

THE

TUNING

CAPA

DRIVE

MECHANISM

coer

The

tuning

capacitor

drive

mechanism

should

be

lubricated

once

or

twice

a

year,

the

interval

de-

pending

upon

the

amount

of

use.

One

drop

of

light

machine

oil

in

each

of

the

holes

in

the

three

bearing

projections

on

the

back

of

the

casting

is

sufficient.

4-6

230

VOLT

POWER

TRANSFORMER

CONVERSION

The

200AB

is

normally

shipped

from

the

factory

with

the

dual

115

volt

primary

windings

of

the

power

transformer

connected

in

parallel

for

operation

from

a

115-volt

a-c

source.

The

windings

can

easily

be

reconnected

in

series

for

operation

from

a

230-volt

a-c

source

if

desired.

Refer

to

the

schematic

drawing

and

note

the

transformer

primary

detail,

To

connect

T2

for

230-volt

operation,

remove

the

jumpers

from

terminals

2-3

and

4-5.

Connect

a

jumper

between

terminals

3-4.

Replace

the

0.8

ampere

slow-blow

fuse

with

one

rated

at

0.4

ampere.

Sect.IV

Page

2

4-7

TROUBLE

SHOOTING

The

following

information

is

designed

to

aid

in

trouble

shooting

a

defective

instrument.

TROUBLE

SHOOTING

CHART

SYMPTOMS

POSSIBLE

CAUSE

TEST

PROCEDURE

Instrument

NOT

|

Line

fuse

blown

due

to|

Replace

fuse,

if

this

fuse

blows

operating,

pilot

|

defective

fuse

or

over-|

remove

V6

and

again

replace

light

NOT

on.

load

in

power

supply|

the

fuse,

If

this

fuse

blows

it

section

of

instrument.

|

indicates:

1.

Short

circuit

in

wiring

asso-

ciated

with

powertransformer.

.

Short

circuit

in

filament

wiring.

1.

Locate

and

clear short

circuit.

2.

Locate

and

clear

short

circuit.

3.

Replace

defective

tube.

3.

Tube

with

an

internal

short

circuit.

.

Defective

power

transformer.

4.

Replace

power

trans-

former.

If

fuse

does

not

blow

with

V6

re-

moved,

it

indicates:

Replace

C12

if

proven

defective,

1.

Defective

filter

capacitor

C12.

DC

resistance

between

8

on

V6

socket

and

ground

is

normally

50,000

ohms

(ap-

proximate)

and

should

be

mea-

sured

with

the

instrument

dis-

connected

from

the

power

line.

2.

Short

in

direct

current

wiring.

2.

Locate

and

clear

short

circuit.

Instrument

NOT

|

Oscillator

section

not

|Measure

oscillator

voltage

between

operating,

pilot

|

operating

properly,

{negative

terminal

of

C8

and

ground;

light

ON.

should

agree

with

the

voltage

speci-

fied

on

schematic.

If

oscillator

voltage

not

present,

check:

1.

Defective

tube.

2.

DC

voltage

in

oscillator

eir-

cuit

(should

agree

with

those

indicated

on

schematic

diagram

within

110%).

3.

Short

circuit

in

tuning

capacitor

or

associated

trimmers.

Short

circuit

in

front

two

sections

of

tuning

capacitor

will

cause

lamp

(R11)

to

flash

intermittently

(lamp

filament

dull

red)

when

the

instrument

is

set

at

1000

cycles/second.

1.

Replace

V1

and

V2.

2.

Replace

component

causing

incorrect

d-c

voltage.

3.

Clear

short

circuit.

If

trimmer

(C2,

C3,

or

C4)is

defective

replace.

If

foreign

material

is

shorting

tuning

capaci-

tor

(C1)

remove

care-

fully

without

bending

plates.

If

plates

have

been

damaged

and

are

touching,

straighten

carefully.

4.

Clean

range

switch

con-

tacts

or

replace

assem-

bly

if

there

are

any

open

or

damaged

resistors.

.

Range

switch

(S1)

to

make

cer-

tain

it

is

making

good

contact

and

that

there

are

no

open

range

resistors.

HP 200AB Owner's manual

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