Philips PM 3344 User manual

PHILIPS

PM

3344

FOUR

TRACE

Y

-AMPLIFIER

944403344001

9499

440

01811

01/0467/00

2

IMPORTANT

In

correspondence

concerning

this

apparatus,

please

quote

the

type

number

and

the

serial

number

as

given

on

the

type

plate

at

the

back

of

theapparatus.

3

Contents

GENERAL

INFORMATION

5

SERVICE

NOTES

9

I.

Introduction

5

V.

Circuit

description

9

II.

Technical

data

5

VI.

Checking

and

adjusting

11

VII.

LIST

OF

PARTS

17

DIRECTIONS

FOR

USE

7

A.

Mechanical

17

B.

Electrical

18

III.

Installation

7

IV.

Controls

and

their

functions

7

List

of

figures

Fig.

1

Front

-view

with

controls

and

sockets

2

Block

-diagram

3

Collector

wave

forms

during

the

switching

4

Collector

wave

forms

if

one

channel

is

switched

off

5

Collector

wave

forms

if

two

channels

are

switched

off

6

Left-hand

side

with

adjusting

elements

7

Right-hand

side

with

adjusting

elements

8

Pulser

TUS

9

Front

view

with

item

numbers

Page

Fig.

Page

6

10

Top

view

with

item

numbers

16

8

11

Attenuator

switch

21

12a

Y

-Amplifier

unit

1

22

11

12b

Y

-Amplifier

unit

1

23

13

Trigger

amplifier

unit

2

25

11

14

Ring

counter

unit

3

25

15

Attenuator

print

unit

7

25

11

16

Decouple

unit

25

12

17

Attenuator,

circuit

diagram

25

12

18

Y

-Amplifier,

circuit

diagram

27

15

19

Trigger

amplifier,

circuit

diagram

29

16

20

Switching

part,

circuit

diagram

29

5

GENERAL

INFORMATION

Introduction

Four

-trace

h.f.

unit

PM

3344

is

a

plug-in

unit

for

the

Y

-channel

of

basic

oscilloscope

PM

3330.

This

unit

comprises

four

identical

amplifiers

and

an

Technical

data

Properties

expressed

in

numerical

values

with

tolerances

stated

are

guaranteed

by

the

factory.

Numerical

values

without

tolerances

stated

represent

the

properties

of

an

average

unit

and

merely

serve

as

a

guide.

The

following

Channels

Input

circuit

input

impedance

input

socket

maximum

permissible

input

voltage

in

position

AC

Amplifiers

deflection

coefficient

bandwidth

rise

time

magnification

polarity

Mode

of

operation

0

electronic

switch,

by

means

of

which

it

is

possible

to

display

four

signals.

The

amplifier

data

apply

to

all

channels.

data

apply

in

case

of

nominal

mains

voltage,

unless

otherwise

stated.

All

data

of

this

unit

apply

when

the

unit

is

used

in

combination

with

main

frame

PM

3330.

4

identical

channels

A...D.

identical

for

channels

A...D.

AC/DC

Push-button

for

checking

zero

level

and

channel

identification.

1

MS2/18

pF

B.N.C.

400

V.

4

identical

amplifiers

for

channels

A...D.

adjustable

to

10

calibrated

values

i.e.

10

mV/cm...

10

V/cm

in

1,

2,

5

sequence.

Tolerance:

-{-

or

—

3%.

Continuous

(non

-calibrated)

adjustment

between

the

steps

is

possible.

in

position

DC:

0

Hz...50

MHz

in

position

AC:

1.6

Hz...50

MHz

7

ns.

Unit

only:

5

ns.

up

to

3

x

the

useful

screen

height

for

frequencies

up

to

10

MHz.

The

peaks

of

a

displayed

picture,

having

maximum

amplitude,

can

be

displayed

by

means

of

the

shift

control.

reversible

for

each

channel.

Channels

A,

B,

C

and

D,

chopped

at

2

MHz.

Channels

A,

B,

C

and

D

alternately.

Each

channel

can

be

switched

off

separately.

Blanking

during

switching.

6

Triggering

required

trace

height

from

any

of

the

four

channels.

3

mm

for

frequencies

up

to

10

MHz.

Phase

difference

between

the

channels

not

visible.

Cross

-talk

at

10

MHz:

<

1%.

Mechanical

data

width

15

cm.

dimensions

depth

29

cm

(controls

and

plug

included)

height

17.5

cm.

weight

3

kg.

Accessories

manual

Optional

probe

identification

set

trimming

tool.

4

measuring

probes

PM

9331

A/10

4

measuring

probes

PM

9334

A/10

SK1

SK2

~-...

~PN~IUPS

PM

3344

FOUR

TRACE

Y

AMPE.

i

z..;

.

-~.~

~"

mcnnv

as..«.

BU1~

SK3

~---~

SK5

SK6

e

BU2—~

SK7

SK9—

SK10

~

BU3—~',

SK11

SK13~

SK14

°

~

BU4~----~

SK15

~~.

SK17

SK18

R1

•~,

,y14R3~z

«~~,

S

K4

R4

R5

R6

R7

R8'

SK8

R9

R10

R11.

R12

R13

SK12

R14

R15

R16

R17

R18

SK16

R19

~'—'

R

20

PEM

3586

Fig.

1.

Front

-view

with

controls

and

sockets

DIRECTIONS

FOR

USE

Installation

The

PM

3344

should

be

plugged

into

the

left

plug-in

compartment

(Y

-UNIT)

of

basic

oscilloscope

PM

3330.

Switching

-on

is

effected

with

the

mains

switch

of

the

basic

oscilloscope.

Approximately

ten

minutes

after

switching

-on

the

unit

Controls

and

their

functions

has

reached

its

operating

temperature

and

meets

the

technical

data.

When

the

PM

3344

is

used,

the

switch

on

the

rear

side

of

the

basic

oscilloscope

should

be

set

to

position

MULTI

-TRACE

CHOPPER.

Channels

A,

B,

C

and

D

are

provided

with

the

following

controls

and

sockets.

CHECK

ZERO

(SKl,

SKS,

SK9,

SK13)

AC

-

DC

(SK2,

SK6,

SK10,

SK14)

V/cm

(SK2,

SK7,

SK11,

SK15)

INVERT

-OFF

-NORM

(SK4,

SK8,

SK12,

SK16)

A,

B,

C,

D

(BU1,

BU2,

BU3,

BU4)

GAIN

ADJ.

(Rl,

R6,

R11,

R16)

DC

-BAL

(R2/R3,

R7/R8,

R12/R13,

R17/R18)

CONT

(R4,

R9,

R14,

R19)

m

When

this

button

is

depressed,

the

connection

between

amplifier

input

and

input

socket

is

interrupted

and

the

amplifier

input

is

earthed.

This

switch

couples

the

input

socket

to

the

amplifier

either

direct

or

capacitively.

By

means

of

this

control

the

deflection

coefficients

may

be

selected

in

steps.

Position

NORM

Position

INVERT

Position

OFF

A

positive

going

input

signal

causes

an

upward

deflection

on

the

screen.

A

positive

going

input

signal

causes

a

down-

ward

deflection

on

the

screen.

The

channel

is

switched

off.

Input

socket

The

deflection

coefficient

of

each

channel

can

be

checked

by

applying

the

calibration

voltage

of

the

basic

oscilloscope

to

the

input

socket.

If

the

deflection

coefficient

does

not

correspond

to

the

indicated

value,

it

can

be

corrected

by

adjusting

screw

-driver

control

GAIN

ADJ.

In

this

case

continuous

control

CONT

should

be

turned

fully

clockwise

(CAL).

The

dc

-balance

of

the

amplifier

can

be

adjusted

with

this

control.

For

this,

remove

the

input

signal

and

adjust

the

time

-base

generator

of

the

basic

oscilloscope

to

its

free

-running

position

(TRIGG.

MODE

to

position

AUT,

or

STAB.

fully

anti

-clockwise).

Adjust

the

DC.

BAL.

so

that

the

line

on

the

screen

does

not

move

when

the

continuous

attenuator

CONT.

is

turned.

This

control

enables

a

continuous

setting

of

the

deflection

coefficients

(control

range

1

:

3).

The

deflection

coefficients

are

calibrated

when

this

control

is

turned

fully

clockwise

(CAL).

8

SHIFT

With

this

knob,

the

trace

can

be

shifted

in

Y

-direction.

(R5,

R10,

R15,

R20)

The

working

-direction

of

this

SHIFT

-control

depends

on

the

position

of

the

polarity

switch.

TRIGG.

A,

B,

C,

D

With

this

push-button

switch

the

triggersignal

can

be

taken

from

channel

(SK17)

A,

B,

C

or

D.

Moreover

it

is

possible

to

suppress

the

display

of

the

triggering

signal

by

positioning

the

relevant

INV-OFF-NORM

selector

to

OFF.

CHOPPED

-ALTERNATE

This

push-button

switch

allows

two

modes

of

operation,

viz.

(SK18)

—CHOPPED.

The

signals

of

each

channel

are

displayed

in

the

sequence

A,

B,

C

and

D

for

500

it

s.

Channels

out

of

operation

are

skipped.

—

ALTERNATE.

The

signals

of

each

channel

are

displayed

successively

in

the

sequence

while

Channels

out

of

operation

are

skipped.

AO

AC

DC

1

CHECK

=Z

RO

V/cn

A~tenu

itor

DC

L'AL

CAIN

0 0

4C

DC

CHECK

ZERO

V/cm

B

~

A~ten~alor

cp

DO

P

ro-ampl

ifier

INV

O4F

NORM

DC

BAL

GAIN

0 0

TRIGG

Vj

Cm

Attenuator

Prc-amplifier

INV

OFF

NORM.

ALTERNATE

CHOppED

Pulse

g

nerator

R

ng

ou

nfer

Electronic

switch

Final

stage

B

T

Trigger

ampl

ifier

Y

-plug

1

Blanking

b

I

1

I

V

-ampl

ifier

Q

I

Alternate

p

Ise

from

time

base

I

~

Q

AC

~

CHECK

ZERO

DC

AC

DC

V/cm

Attenuator

Pre-ampl

Ifier

DC

BAL

GAIN

CHECK

ZERO

Fig.

2.

Block

-diagram

Pre-ampl

Iflee

NORM.

OFF

NV

0 0

DCB

L

GAIN

~^

NORM.

OFF

INV

PEM

3528

I

Tngger

amplifier

~

O

9

SERVICE

NOTES

Circuit

description

A.

PREAMPLIFIER

CHANNEL

A

(Fig.

18)

0

The

incoming

signal

is

fed

to

a

ten

step

attenuator,

direct

or

via

a

capacitor,

depending

on

the

position

of

switch

AC

—

DC

(SK3)

which

reduces

the

signal

amplitude

by

a

factor

1,

2,

5,

10

etc.

up

to

1000,

as

selected

with

switch

V/cm

(SK3).

Cathode

follower

B

101

provides

an

impedance

transformation

to

drive

the

following

transistor

amplifier.

A

second

cathode

follower

B

101

is

sym-

metrically

connected

to

B101,

to

minimise

drift.

Furthermore,

a

provision

is

made

to

balance

the

amplifier

by

varying

the

grid

potential

of

B

101'

with

DC.

BAL

(R3

coarse

and

R2

fi

ne).

When

CONT

(R4)

has

been

properly

adjusted,

no

signal

will

be

present

across

it,

if

the

grid

circuit

of

B

101

is

connected

to

-earth

with

switch

CHECK

ZERO

(SK1).

The

transistor

amplifier

is

protected

by

diodes

GR101-102-103.

The

second

stage

is

formed

by

emitter

-followers

TS

101

and

TS

102.

They

offer

a

low

impedance

signal

source

for

the

and

for

the

trigger

-amplifier

which

receives

its

signals

via

R120

and

R130.

As

continuous

attenuator

CONT

(R4)

and

gain

adjust-

ment

GAIN

ADJ

(R1)

are

connected

between

the

emitters

of

this

stage,

no

shift

will

occur

in

case

of

correct

do

balance,

when

continuous

attenuator

CONT

(R4)

is

operated

(the

emitters

have

the

same

do

poten-

tial).

Moreover,

the

trigger

voltage

is

balanced

before

it

is

applied

to

the

trigger

amplifier.

The

third

stage

and

the

fi

rst

stage

of

the

fi

nal

amplifier

form

the

series

and

the

shunt

feed

—back

transistor

circuit

TS103

—

TS501,

in

push-pull

with

an

identical

circuit

TS104

—

TS503.

The

amplification

factor

of

this

circuit

is

mainly

determined

by

the

ratio

of

the

values

of

R506

(or

R517)

and

the

resistance

at

the

emitter

of

TS

103

(or

TS

104)

and

resistor

R508

(or

R516).

By

means

of

potentiometer

SHIFT

(RS)

in

the

emitter

circuit

of

TS

103

—

TS

104

the

currents

in

these

tran-

sistors

can

be

varied.

This

variation

results

in

a

vertical

shift

of

the

display.

Capacitors

C111

and

C112

and

resistor

R142

provide

a

square

-wave

response

correction.

Resistors

R134

—

R146

and

R124

—

R129

provide

a

constant

dissipation

of

the

transistors

so

that

no

sag

occurs

in

case

of

square

waves.

of

low

frequency.

Between

the

third

stage

and

the

fi

nal

amplifier,

switch

NORMAL

-OFF

-INVERT

(SK4)

has

been

inserted.

This

is

a

3

-position

rotary

switch.

In

the

fi

rst

and

the

third

position

the

leads

of

the

pre

-amplifier

and

the

electronic

switch

are

interchanged

so

that

the

signal

is

inverted

180°.

In

centre

position

of

the

switch

the

channel

is

dis-

connected

from

the

output

amplifier

by

means

of

the

electronic

switch.

When

three

channels

are

switched

off,

the

pulse

gener-

ator

is

stopped

and

no

blanking

pulses

are

fed

to

the

cathode-ray

tube.

The

INV-OFF-NORMAL-switch

(SK4)

is

followed

by

the

electronic

switch

consisting

of

diodes

GR104,

GR106...GR109

and

GR111

and

the

resistors

R144,

R

147

and

R

148.

A

pulse

from

the

ring

counter

is

fed

to

junctions

GR107

—

GR109

and

GR106

—

GR108.

If

the

pulse

from

the

ring

counter

is

negative

with

respect

to

the

input

level

of

the

output

stage,

diodes

GR106...GR109

will

be

blocked

while

GR104

and

GR111

are

conductive.

This

means

that

the

relevant

pre

-amplifier

is

connected

to

the

output

stage.

If

the

pluse

of

the

ring

counter

is

positive

with

respect

to

the

input

level

of

the

output

stage,

diodes

GR106...

GR109

will

become

conductive

and

GR104

andGRl

ll

will

be

blocked.

The

output

stage

is

now

switched

off

from

the

relevant

pre

-amplifier.

The

pre

-amplifier

is

then

supplied

with

current

from

the

ring

counter

via

conductive

diodes

GR106...

GR109.

As

a

blocked

diode

always

possesses

a

certain

capaci-

tance

there

is

some

capacitive

transmission

of

the

signal.

To

minimize

this

the

circuit

is

doubled.

GR106

and

GR108

short-circuit

the

signal

after

which

any

remaining

signal

is

further

attenuated

by

resistors

R147

and

R148

and

conductive

diodes

GR107

and

GR

109.

R144

serves

to

equalize

the

current

through

GR106

—

GR108

and

GR107

—

GR109.

10

B.

PREAMPLIFIER

CHANNELS

B,

C

AND

D

(Fig.

18)

These

pre

-amplifiers

are

identical

to

that

of

channel

A.

The

components

of

channel

B

are

numbered

one

hun-

dred

higher

than

those

of

channel

A,

those

of

C

two

hundred

higher

than

those

of

channel

A,

and

those

of

D

three

hundred.

The

controls

and

sockets

form

an

exception.

For

them

see

Fig.

1.

C.

FINAL

AMPLIFIER

This

amplifier

consists

of

two

push-pull

amplifier

stages:

—

TS501

and

TS503,

which

are

part

of

the

series

and

shunt

feedback

circuit

already

discussed.

The

input

voltage

required

for

the

electronic

switch

is

obtained

by

setting

the

emitters

of

this

stage

to

a

fi

xed

voltage

by

means

of

a

Zener

diode.

—

two

output

emitter

followers

TS502

and

TS504

feeding

the

signal

to

the

basic

oscilloscope

PM

3330.

D.

TRIGGER

AMPLIFIER

(Fig.

19)

The

triggersignal

can

be

picked

up

from

each

channel.

The

choice

is

made

by

means

of

push-button

switch

TRIGG.

A,

B,

C,

D

(SK17).

The

triggersignal

is

fed

to

a

transistorized

trigger

-

amplifier

consisting

of:

—

a

push-pull

series

and

shunt

feedback

circuit

(TS601—

TS602

and

TS604

—

TS606).

R607

and

R608

compensate

for

thermal

drift

of

TS601

—

TS604,

which

improves

the

square

-wave

response.

—

a

push-pull

emitter

follower

output

stage

(TS603

—

TS607)

through

which

the

signal

is

fed

to

basic

oscilloscope

PM

3330.

The

do

balance

of

the

trigger

amplifier

is

adjusted

with

R611.

E.

PULSE

GENERATOR

This

generator

comprises

a

blocking

oscillator

(Fig.

20).

In

position

CHOPPED

(SK18),

switch

SK18b

is

opened.

The

base

potential

of

TS707,

which

is

determined

by

voltage

divider

R756

—

R757,

is

such

that

the

blocking

oscillator

is

free

running.

The

repetition

rate

of

the

oscillator

signal

is

determined

by

the

time

constant

of

the

RC

-network

in

the

emitter

circuit

of

TS707

and

amounts

to

2

MHz.

When

the

base

potential

is

equal

to

or

positive

with

respect

to

the

emitter

potential,

the

oscillator

stops.

This

happens

in

two

cases:

—

When

three

amplifiers

are

switched

off.

By

means

of

diode

GR701

the

base

potential

will

be

driven

to

a

positive

value

with

respect

to

the

emitter

and

the

blocking

oscillator

will

be

switched

off,

so

that

no

further

pulses

come

from

the

oscillator

and

no

beam

suppression

takes

place.

—

In

position

ALTERNATE

(SK18)

switch

SK18e

is

closed.

Resistor

R757

is

short-circuited

and

the

base

potential

will

be

equal

to

the

emitter

potential.

At

the

same

time

the

alternate

pulse

from

the

PM

3330

will

be

fed

to

the

base

of

TS706

after

differentiation

by

C714

—

R752.

The

collector

of

this

transistor

is

connected

to

a

winding

S3

of

the

blocking

transformer

so

that

an

incoming

alternate

pulse

produces

a

negative

pulse

on

the

base

of

TS707.

Consequently

the

blocking

oscillator

will

operate

once

for

each

arriving

alternate

pulse.

Winding

S3

also

serves

to

supply

the

blanking

pulse.

Diode

GR702,

connected

in

parallel

to

S3,

ensures

that,

when

the

blocking

oscillator

is

switched

off

rapidly,

the

polarity

of

the

voltage

across

the

trans-

former

does

not

change;

this

could

cause

undesirable

restarting

of

the

ring

counter.

F.

RING

COUNTER

(Fig.

20}

The

ring

counter

consists

of

four

emitter

coupled

transistors

TS701...TS704,

so

connected

that

if

one

draws

current,

the

other

three

are

blocked.

This

has

been

achieved

by

coupling

the

collector

of

each

transistor

to

the

base

of

the

other

three,

by

means

of

voltage

dividers.

The

collectors

of

the

transistors

are

also

capacitively

(C701...C704)

coupled

to

the

base

of

the

sistor

via

the

INVERT

-OFF

-NORMAL

switch

(SK4,

SK8,

12,

16).

At

each

incoming

positive

pulse

from

the

blocking

oscillator

the

current

through

the

conductive

transistor

will

fall

off

to

zero

for

a

moment,

so

that

the

collector

becomes

positive.

Via

the

above

-mentioned

capacitor

this

surge

is

fed

to

the

base

of

the

which

becomes

conduc-

tive.

This

process

is

repeated

each

pulse

from

the

blocking

oscillator

(in

position

CHOPPED

every

500

ns

and

in

position

ALTERNATE

at

every

fl

y

-back

of

the

time

base).

The

pulse

generator

is

coupled

to

the

ring

counter

by

means

of

a

diode

so

that

only

the

peak

of

the

pulse

is

fed

to

the

ring

counter.

The

voltage

wave

forms

at

the

collectors

of

the

ring

counter

transistors

are

shown

in

Fig.

3.

11

The

collectors

of

the

ring

counter

are

connected

to

the

electronic

switch.

As

already

mentioned

in

chapter

V

A,

the

relevant

channels

can

be

switched

on

or

off

with

a

negative

and

positive

voltage

respectively.

If

a

channel

is

not

used

(INV-OFF-NORMAL

(SK4,

8,

12,

16

switch

to

position

OFF),

the

transistor

in

the

ring

counter

corresponding

to

this

channel

is

cut

off

by

connecting

the

base

to

the

negative

supply

voltage

via

a

resistor

(R702

or

R704

or

R707

or

R709).

Moreover,

the

capacitor

connected

between

the

pre-

ceeding

collector

and

the

relevant

base

is

switched

over

to

the

base

of

the

transistor.

The

collector.

wave

forms

are

shown

in

Fig.

4.

The

collector

wave

forms

with

two

channels

switched

off

are

shown

in

Fig.

5.

The

switching

frequency

in

CHOPPED

position

is

always

2

MHz,

so

that

in

this

position

a

different

channel

is

displayed

every

500

ns.

PEM

3529

Fig.

3.

Collector

waveforms

during

Fig.

4.

Collector

wave

.

forms

if

one

Fig.

S.

Collector

wave

forms

if

two

the

switching

channel

is

switched

off

Checking

and

adjusting

A.

GENERAL

The

tolerances

mentioned

are

factory

tolerances;

they

apply

when

the

apparatus

is

readjusted

completely.

They

may

differ

from

the

data

given

in

II.

With

the

aid

of

these

data,

it

is

possible

to

carry

out

all

the

adjustments

to

four

-trace

unit

PM

3344

and

to

check

the

proper

working

of

the

plug-in

unit.

For

this,

the

unit

should

be

inserted

into

the

Y

-plug-in

compartment

of

a

correctly

adjusted

basic

oscilloscope

PM

3330.

Some

of

the

adjusting

elements

areon

the

right-hand

side

of

the

unit

and

are

not

directly

accessible.

When

these

elements

should

be

adjusted,

the

unit

should

be

connected

to

the

basic

oscilloscope

via

the

rigid

extension

plug.

(for

the

code

number

of

this

plug,

see

the

list

of

accessories

of

PM

3330).

For

a

complete

adjustment

of

the

instrument

the

sequence

as

described

in

this

chapter

is

to

be

preferred.

B.

D

C/BALANCE

channels

are

switched

off

This

adjustment

should

be

carried

out

when

the

unit

has

obtained

its

operating

temperature,

i.e.

30

minutes

after

switching

-on.

Set

the

knobs

of

the

basic

oscilloscope

to

the

following

positions:

TRIGG.

MODE

(SK1)

to

AUT.

~/—

(SK2)

to

-~-

TRIGG.

SOURCE

(SK3)

to

INT.

TIME/cm

(SK4)

to

.5

msec.

X

-DEFLECTION

(SK7)

to

TIME

BASE

A.

1.

Channel

A

(B,

C,

D)

R2

(R7,

12,

17)

(Fig.

1)

R135

(R235,

335,

435)

(Fig.

6)

-

Set

INV-OFF-NORM.

SK4

(SK8,

SK12,

SK16)

to

NORM.

-

Set

potentiometers

DC-BAL,

R2

(R7,

R12,

R17)and

Philips PM 3344 User manual

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