Tektronix 531 User manual

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CATHODE

RAY

OSCILLOSCOPE

TYPE

531/541

INSTRUCTION

MANUAL

TEKTRONIX,

INC.

MANUFACTURERS

OF

CATHODE-RAY

AND

VIDEO

TEST

INSTRUMENTS

Sunset

Highway

and

Barnes

Road

¢

P.O.Box

831

©

Portland

7,

Oregon,

U.

S.A.

Phone:

CYpress

2-2611

¢

Cables:

Tektronix

070-203

NOTE

This

instruction

manual

has

been

prepared

to

cover

TEKTRONIX

Type

531/541

Oscilloscopes

of

all

serial

number

ranges.

Text,

diagrams,

and

parts

lists

have

been

expanded

to

incorporate

all

circuit

modifications

adopted

during

the

course

of

manufacture.

The

serial

ranges

of

instruments

to

which

various

modifications

were

applied

before

shipping

from

the

factory

have been

noted

wher-

ever

necessary.

However,

because

many

instruments

have

been

modified

in

the

field

and

out

of

serial

sequence,

component

values

and

circuitry

of

a

given

instru-

ment

may

differ

considerably

from

those

indicated

in

this

manual

for

its

serial

number.

Theuser

is

urged,

therefore,

to

enter

whatever

changes

may

be

necessary

to

bring

this

manual

intoagreement

with

the

present

circuitry

of

his

oscilloscope.

When

ordering

parts,

always

include

the

fol-

lowing

information:

Instrument

Type

(531/541).

Instrument

Serial

Number

(as,

S/N

9999).

Part

Circuit

Number

(as,

R999).

Part

Description

(value,

type,

rating,

tolerance,

etc.).

5.

The

6-digit

TEKTRONIX

part

number

(as,

999-999),

kone

SAFETY

NOTICE

This

oscilloscope

employs

dangerously

high

voltages,

Since

some

maintenance

must

of

necessity

be

performed

with

the

case

removed,

great

care

should

be

taken.

Use

only

insulated

tools,

stand

on

a

dry

floor

and

if

possible

keep

one

hand

in

your

pocket.

Care

should

also

be

used

in

making

any

con-

nections

to

the

deflection

plates

of

the

cathode-ray

tube

through

the

access

panel.

It

is

advised

that

the

access

panel

never

be

removed

until

the

power

has

first

been

turned

off.

The

instru-

ment

should

not

be

operated

with

this

protective

cover

removed,

CONTENTS

GENERAL

DESCRIPTION

SECTION

1

Characteristics.

Functions

of

Front-Panel

Controls

and

Connectors.

OPERATING

INSTRUCTIONS

SECTION

2

Preliminary

Instructions.

First-Time

Operation.

Triggering

Modes.

‘Triggering

Instructions.

Sweep

Operation.

Auxiliary

Functions.

Sim-

plified

Sweep

Diagrams.

CIRCUIT

DESCRIPTION

SECTION

3

Block

Diagram.

Vertical-Deflection

System.

Horizontal-Deflection

System.

Power

Supply.

CRT

Circuit.

MAINTENANCE

SECTION

4

General

Information.

Trouble

Shooting.

Recalibration

Procedure.

PARTS

LIST

SECTION

5

SECTION

1

GENERAL

DESCRIPTION

NOTE

The

Types

531

and

541

are

high-speed

laboratory

oscilloscopes,

designed

for

general

laboratory

use.

Their

extremely

fast

rise-

time,

wide

sweep-speed

range

and

10-kilovolt

accelerating

volt-

age

permit

accurate

analysis

of

many

types

of

waveforms.

Addi-

tional

adaptability

is

provided

by

plug-in

preamplifiers

which

extend

the

use

of

these

oscilloscopes

to

practically

all

laboratory-

oscilloscope

applications.

Accurately

calibrated

sweep

speeds

and

vertical-deflection

sensitivity

permit

quantitative

time

and

amplitude

measurements

to

be

made.

CHARACTERISTICS

Cathode-Ray

Tube

A

Tektronix

5-inch

post-deflection

accelera-

tion

cathode-ray

tube

is

furnished

with

the

in-

strument.

With

10-kv

acceleration

potential

the

trace

is

bright

enough

that

a

single

sweep

can

be

photographed

with

a

Pll

screen

even

at

the

fast-

est

sweep

speeds.

A

P2

phosphor

is

furnished

unless

other

phosphors

are

specially

requested.

Vertical-Deflection

System

A

dc-coupled

vertical

amplifier

in

the

main

unit

is

adjusted

for

optimum

transient

response

and

wide

passband.

A

plug-inchannel-switching

unit

provides

a

dual-trace

presentation

for

re-

petitive

signals.

Input

to

the

vertical-deflection

system

must

be

made

through

one

of

the

avail-

able

types

of

plug-in

units.

Horizontal-Deflection

System

Sweep

Circuit

The

linear

sweep

generator

is

a

Miller

runup

generator

with

excellent

linearity,

and

the

ex-

tremely

wide

speed range

of

.02

microseconds

per

centimeter

to

12

seconds

per

centimeter.

Twenty-four

calibrated

sweep

speeds

are

avail-

able

accurate

within

three

per

cent.

The

main

sweep

control

has

eight

positions,

.1,

1,

10,

and

100

microseconds

per

centimeter,

1,

10,

100

milliseconds

per

centimeter,

and

1

second

per

centimeter.

Three

multiplier-switch

positions

1, 2,

and

5

times,

provide

a

total

of

twenty-

four

speeds.

Remaining

positions

of

the

multi-

plier

switch

provide

continuously

adjustable

ie

531/54I—GENERAL.

DESCRIPTION

multipliers

of

1

to

2.5

times,

2

to

5

times,

and

5

to

12

times

so

that

the

above

range

is

also

covered

continuously.

The

five-times

sweep

magnifier

increases

the

maximum

sweep

speed

to

.02

microseconds

per

centimeter.

Magnifier

Sweep

magnification

is

produced

by

increasing

the

sweep

output

amplifier

gain

five

times.

The

center

two

centimeters

of

the

trace

is

expanded

to

10

centimeters,

Any

one-fifth

of

the

sweep

so

magnified

can

be

positioned

to

show

on

the

screen

by

means

of

the

HORIZONTAL

POSI-

TION

control.

DC-Coupled

Unblanking

The

unblanking

square

wave

is

dc-coupled

to

the

grid

of

the

cathode-ray

tube

to

assure

uni-

form

unblanking

bias

for

all

sweep

times

and

repetition

rates.

Triggering

System

The

sweep

can

be

triggered

by

a

wide

range

of

triggering

voltages

either

derived

internally

from

the

signal

to

be

displayed,

or

through

a

front-panel

connector

from

an

external

source.

The

circuit

permits

the

sweep

to

be

triggered

from

any

selected

point

along

the

triggering

waveform.

A

recurrent

triggering

arrangement

which

runs

at

a

fifty-cycle

repetition

rate

will

synchronize

with

repetitive

trigger

signals

from

sixty

cycles

to

two

megacycles.

PAGE

1-1

Horizontal-Deflection

Amplifier

A

de-coupled

horizontal-deflection

amplifier

provides

horizontal

sensitivity

of

2

volts

per

centimeter

to

approximately

15

to

20

volts

per

centimeter,

continuously

adjustable

by

means

of

a

ten-to-one

continuously

adjustable

control

and

a

10X

and

1X

switched

attenuator.

Because

this

amplifier

was

designed

for

op-

timum

performance

with

a

sweep

sawtooth,

its

performance

with

sine

waves

is

limited.

This

sine-wave

limitation

can

best

be

defined

by

an

amplitude-frequency

product,

which

can

be

ex-

ceeded

only

at

the

expense

of

considerable

dis-

tortion.

The

amplitude-frequency

product

is

2.4

centimeter-megacycles.

Thus

a

full

10-

centimeters

of

deflection

can

be

used

at

240

kc,

and

a

2.4-me

sine

wave

can

be

viewed

if

the

amplitude

is

one

centimeter

peak-to-peak

or

less.

The

amplifier

frequency

response

toa

sine

wave

is

down

less

than

30%

at

400

kc

when

the

amplitude

is

within

this

limitation.

Output

Waveforms

Available

Front-panel

connectors

provide

a

positive-

going

sawtooth,

a

positive

gate

synchronized

with

the

sweep,

and

a

signal

derived

from

the

displayed

vertical

signal.

The

calibrator

pro-

vides

an

adjustable

amplitude

symmetrical

square

wave

with

a

repetition

rate

of

about

one

kilocycle,

The

amplitude

is

adjustable

intwenty

steps

between

.2

millivolts

and

100

volts.

Power

Supply

All

de

voltages

are

regulated

to

accommodate

line-voltage

variations

between

105

and

125

volts

or

210

volts

to

250

volts,

50

to

60

cycles,

ac,

and

for

the

differences

in

dc

loads

imposed

by

the

different

plug-in

units.

Power

Consumption

At

117

or

234

volts,

475

watts

with

plug-

in

unit

in

place.

Cooling

Safe

operating

temperature

is

maintained

with

filtered,

forced-air

ventilation.

A

thermal

dis-

connect

device

turns

off

the

ac

power

in

the

event

the fan

fails

or

the

air

intake

becomes

blocked.

Illuminated

Graticule

The

graticule

is

accurately

scribed

in

centi-

meters

and

fifths

of

centimeters.

The

scribed

lines

can

be

edge-lighted

either

by

white

or

by

red

light.

A

green

filter

is

supplied

to

increase

contrast

in

the

presence

of

room

brightness.

At

extra

cost,

a

light

shield

is

available

con-

structed

so

that

it

will

slip

onover

the

graticule

bezel.

Mechanical

Characteristics

Construction

The

cabinet

and

chassis

are

madeof

electric-

ally-welded

aluminum

alloy.

Finish

Photo-etched

anodized

aluminum

-alloy

panel,

wrinkle-enameled

cabinet.

Dimensions

24

inches

long,

13

inches

wide,

16-3/4

inches

high.

Weight

61-1/2

pounds.

FUNCTIONS

OF

FRONT-PANEL

CONTROLS

AND

CONNECTORS

TRIGGERING

MODE

(red

knob)--Five-position

switch

arranges

trigger

circuits

for

five

kinds

of

triggering:

DC,

AC

SLOW,

AC

FAST,

AUTOMATIC

and

HF

SYNC,

In

Type

531

instruments,

S/N

101-6010

and

in

Type

541,

S/N

101-5414,

AUTOMATIC

is

labeled

AC

AUTO,

In

Type

531,

S/N

101-592,

there

is

no

HF

SYNC

position.

PAGE

1-2

TRIGGER

SLOPE--Six-position

switch

selects

source

of

trigger

signal

and

converts

to

negative-going

output,

either

negative-going

Or

positive-going

input.

TRIGGER

INPUT--UHF

coax

connector

to

trig-

gering

circuits

through

EXT

positions

of

TRIGGER

SLOPE

switch.

531/541—GENERAL

DESCRIPTION

STABILITY

(red

knob)--Contro]

for

adjusting

the

stability

of

the

sweep

circuits

for

a

stable

display.

The

control

has

a

PRESET

position

suitable

for

most

triggering

ap-

plications.

Type

531,

S/N101-6710,

and

Type

541,

S/N101-5942,

have

no

PRESET

position

on

the

STABILITY

control.

TRIGGERING

LEVEL--Potentiometer

deter-

mines

part

of

triggering

waveform

where

sweep

triggers.

TIME/CM-

-Eight-position

switch

selects

timing

capacitors

to

determine

sweep

speeds,

and

determine

duration

of

trigger

holdoff

period.

MULTIPLIER-

-Six-position

switch.

Three

po-

sitions

place

precision

charging

resistors

in

series

with

timing

capacitors

to

determine

sweep

speeds

in

conjunction

with

selected

timing

capacitor.

Three

positions

,

marked

in

red,

place

adjustable

charging

voltages

in

series

with

timing

capacitors

for

contin-

uous

control

of

sweep

speeds.

5X

MAGNIFIER--Two-position

switch

removes

or

inserts

feedback

in

sweep

amplifier

to

change

sweep

speeds

by

a

factor

of

five.

HORIZONTAL

DISPLAY--Three-position

switch

connects

sweep

amplifier

to

internal

sweep

generator

in

one

position,

or

to

front

panel

connector

directly

or

through

10-1

fixed

attenuator

in

second

and

third

positions.

EXTERNAL

SWEEP

ATTENUATOR,

10-1---

Continuously

adjustable

gain

control

on

hor-

izontal

amplifier.

Switched

out

of

circuit

for

internal

sweeps.

EXTERNAL

SWEEP

IN--Front-panel

connector

to

horizontal

amplifier

through

HORIZON-

TAL

DISPLAY

switch.

Magnifier

must

be

switched

to

ON

for

undistorted

10-cm

deflection.

VERT.

SIG.

OUT--Front-panel

connector

sup-

plies

signal

from

vertical

amplifier

via

trigger

cathode

follower.

HORIZONTAL

POSITION--

Positions

trace

along

horizontal

axis.

al

531/541—-GENERAL

DESCRIPTION

VERNIER

(red

knob)-

-Fine

adjustments

of

hori-

zontal

positioning,

with

five

times

the

reso-

lution

of

the

coarse

adjustment.

SQUARE-WAVE

CALIBRATOR

(red

knob)---

-

Three-position

switch

turns

on

calibrator

plate

voltage

and

switches

in

or

out

1000-

to-1

voltage

divider

to

give

either

volts

or

millivolts

output.

SQUARE-WAVE

CALIBRATOR

(black

knob)---

Nine-position

switch

selects

nine

taps

on

precision

voltage

divider

in

calibrator

cir-

cuit.

Provides

accurate

voltages

of

.2,

.5,

1,

2,

5,

10,

20,

50,

and

100

volts

in

VOLTS

position,

or

millivolts

in

the

MILLIVOLTS

position

of

the

red

concentric

control

knob.

CAL

OUT---UHF

coax

front-panel

connector

from

the

calibrator.

+GATE

OUT---Front-panel

binding

post

sup-

plies

positive

20-volt

square

pulse,

dc-cou-

pled

through cathode

follower

,

synchronized

with

the

internal

sweep.

SAWTOOTH

OUT---Front-panel

binding

post

supplies

150-volt

positive-going

sawtooth

dc-coupled

through

cathode

follower,

syn-

chrenized

with

the

internal

sweep.

POWER---On-off

switch

in

primary

of

power

transformer

and

ventilating-fan

lead.

FOCUS--

Adjustable

voltage

for

the

cathode-ray

tube

focusing

grid.

INTENSITY--Bias

adjustment

to

cathode-ray

control

grid.

ASTIGMATISM-

Adjustable

voltage

for the

astig-

matism

grid

of

the

cathode-ray

tube.

SCALE

ILLUM-

-Adjustable

series

resistor

con-

trols

voltage

across

graticule

lights.

Beam-

position

indicators,

unlabeled,

marked

with

arrows.

Thé

arrow

nearest

the

illuminated

indicator

shows

which

way

the

beam

is

off

the

screen

if

it

cannot

be

seen.

Rear

of

Cabinet

CRT

CATHODE--Binding

post

connects

to

crt

cathode

through

high-voltage

capacitor.

In-

put

impedance

8

k

to

15

k.

Discharge

time

eonstant

about

15

milliseconds.

PAGE

1-3

SECTION

2

OPERATING

INSTRUCTIONS

PRELIMINARY

INSTRUCTIONS

Cooling

The

Oscilloscope

is

cooled

by

filtered,

forced-

air

ventilation.

The

instrument

must

therefore

be

placed

so

the

air

intake

is

not

blocked,

and

the

filter

must

be

clean

enough

to

permit

ade-

quate

air

circulation.

If

the

interior

tempera-

ture

does

rise

too

high

for

some

reason,

a

thermal

cutout

switch

will

disconnect

the

power

and

keep

it

disconnected

until

the

temperature

drops

to

a

safe

value.

Time-Delay

DC

Power

Relay

A

time-delay

relay

delays

application

of

the

rectified

dc

to

the

circuits

long

enough

for

all

heaters

to

reach

operating

temperature.

The

time

delay

is

approximately

25

seconds,

If

you

switch

the

ac

power

off,

even

briefly,

the

time-

delay

relay

will

delay

reapplication

of

the

dc.

Cathode-Ray

Tube

Controls

The

Tektronix

cathode-ray

tube

inthis

instru-

ment

has

a

total

accelerating

voltage

of

10,000

volts.

The

spot

intensity

with

this

amount

of

acceleration

can

be

bright

enough

to

damage

the

screen

in

a

short

time

if

the

spot

is

left

in

one

place.

Be

careful

not

to

leave

a

fixed

bright

spot

or

slow

sweep

on the

screen.

Turn

the

INTENSITY

control

counterclockwise

so

that

the

spot

is

dim

whenever

you

leave

the

instru-

ment

unattended.

The

separate

FOCUS,

ASTIGMATISM

and

IN-

TENSITY

controls

are

somewhat

interdependent,

and

may

require

readjustment

for

different

IN-

TENSITY

control

settings.

Illuminated

Graticule

The

adjustable

graticule

lighting

control

la-

beled

SCALE

ILLUM.,

can

be

adjusted

to

suit

the

lighting

conditions

of

the

room.

Thecolored

filter

supplied

is

colored

to

provide

the

maximum

trace

contrast

for

the

P2

phosphor

in

the

pres-

ence

of

room

light.

The

graticule

is

accurately

scribed

in

centi-

meters

and

fifths

of

centimeters.

These

scale

markings

and

the

calibrated

fixed

vertical-de-

flection

sensitivities

and

sweep

times,

can

be

used

to

convert

deflections

in

centimeters

into

volts

and

seconds.

Vertical

sensitivities

are

calibrated

in

volts

per

centimeter,

and

hori-

zontal

sweep-times

are

calibrated

in

seconds

per

centimeter,

which,

if

multiplied

by

centimeters

of

deflection,

give

volts

and

seconds.

The

graticule

can

be

mounted

in

either

of

two

positions

rotated

180

degrees

from

each

other.

In

one

position,

the

graticule

illumination

is

colored

red,

and

in

the

other

position

in

white.

The

white

will

reproduce

well

photographically.

FIRST-TIME

OPERATION

First

get

atrace

onthe

screen

by

the

simplest

method,

and

then

proceed

with

the

presentation

you

want

after

you

get

an

idea

of

the

functions

of

the

controls

To

get

a

simple

trace

on

the

screen,

insert

a

preamplifier,

and

proceed

as

follows:

Turn

the

POWER

switch

to

OFF.

Connect

the

power

cord

toa

source

of

117-volt,60-cycle

pow-

er.

Then

set

the

front-panel

controls

as

follows:

INTENSITY

Counterclockwise

(CCW)

FOCUS

eo

Center

531/541-OPERATING

INSTRUCTIONS

ASTIGMATISM

Center

POWER

ON

TRIGGERING

LEVEL

CCW

STABILITY

(red

knob)

PRESET

or

CCW

TRIGGER

SLOPE

+

INT

PAGE

2-1

TRIGGERING

MODE

(red)

Connect

a

lead

between

the

CAL,

OUT

ter-

AUTOMATIC

or

AC

AUTO

minal

and

the

INPUT

terminal

of

the

unit.

Set

TIME/CM

100

MICRO

SEC

MULTIPLIER

2

HORIZONTAL

DISPLAY

INTERNAL

SWEEP

HORIZONTAL

POSITION

Center

SQUARE-WAVE

CALIBRATOR

5

VOLTS,

MILLIVOLTS,

OFF

VOLTS

the

controls

of

the

plug-in

as

follows:

AC--DC

AC.

VOLTS/CM

2

VARIABLE

Clockwise

VERTICAL

POSITION

Center

When

the

POWER

switch

has

been

turned

on

for

about

one

minute,

turn

the

INTENSITY

control

clockwise

until

you

can

see

a

trace

on

the

screen.

With

the

calibrator

waveform

dis-

played,

you

can

set

the

FOCUS,

INTENSITY

,

and

ASTIGMATISM

controls

for

a

sharp

line,

and

position

the

trace

near

the

screen

center

with

the

HORIZONTAL

POSITION

and

VERTICAL

POSITION

controls.

TRIGGERING

MODES

Automatic

You

are

now

displaying

the

calibrator

wave-

form,

whose

repetition

rate

is

about

one

kilo-

cycle,

and

whose

amplitude

is

five

volts,

peak-

to-peak,

with

the

AUTOMATIC

mode

of

trigger-

ing.

This

is

about

the

simplest

mode

of

trigger-

ing.

It

is

useful

for

general

purpose

viewing,

and

will

operate

satisfactorily

for

a

wide

variety

of

trigger

signals

whose

repetition

rates

are

be-

tween

sixty

cycles

and

about

two

megacycles.

AC

Slow

When

you

have

a

good,

well-focused

trace

of

the

calibrating

waveform

by

the

AUTOMATIC

mode

of

triggering,

try

the

other

four

TRIG-

GERING

MODE

switch

positions.

Turn

the

switch

to

the

AC

SLOW

position.

Advance

the

TRIGGERING

LEVEL

control

clockwise

until

you

getastable

trace

again.

There

may

be

a

con-

siderable

range

of

the

LEVEL

control

over

which

you

can

get

a

stabletrace,and

the

start

of

the

trace

will

move

up

and

down

the

edge

of

the

square

wave

within

this

range.

Notice

that

the

trace

starts

on

the

upgoing

partof

the

calibrator

square

wave.

Now

turn

the

TRIGGER

SLOPE

switch

to

the

-INT

position,

and

readjust

the

TRIGGER-

ING

LEVEL

to

obtain

a

stable

trace

again.

No-

tice

now

that

the

trace

starts

on

the

down-going

portion

of

the

trace

and

that

the

position

of

the

PAGE

2-2

start

can

again

be

changed

somewhat

with

the

LEVEL

control.

DC

Triggering

Now

turn

the

TRIGGERING

MODE

switch

to

DC,

Adjust

the

LEVEL

control

for

stable

trig-

gering,

and

then

position

the

trace

with

the

VERTICAL

positioning

control.

You

will

notice

that

triggering

occurs

at

a

vertical

level

on

the

screen

selected

by

the

LEVEL

control

and

that

the

triggering

point

changes

relative

to

the

waveform

as

the

waveform

is

positioned

verti-

cally.

This

effect

will

be

more

noticeable

if

you

look

at

a

low-frequency

sine

wave.

This

triggering

position

is

most

useful

for

low-frequency

signals.

Ir

is

not

suitable

for

applications

where

the

de

level

is

changing

such

as

when

a

Dual-Trace

Unit

is

being

used.

AC

Fast

In

the

AC

FAST

position

of

the

TRIGGERING

MODE

switch,

the

circuit

is

quite

similar

to

that

in

the

AC

SLOW

position,

and

you

will

notice

no

difference

when

displaying

the

cali-

brator

waveform.

The

only

difference

is

thatan

re

filter

is

inserted

in

the

circuit,

making

it

insensitive

to

low

frequencies,

and

allowing

it

to

recover

quickly

from

de

level

changes.

This

is

the

position

to

use

when

there

is

hum

present.

This

is

also

the

best

position

to

use

with

the

mn

531/541-OPERATING

INSTRUCTIONS

alternate

sweep

feature

of

the

53/54C

unit

if

you

use

INTernal

triggering

with

signals

having

fre-

quency

components

above

10

kc.

HF

Sync

The

HF

SYNC

position

of

the

TRIGGERING

TRIGGERING

Triggering

Level

The

TRIGGERING

LEVEL

control

selects

the

point

on

the

triggering

waveform

at

which

trig-

gering

will

occur.

To

trigger

on

small

signals

this

control

must

be

set

near

O,

or

near

the

dc

level

with

dc

triggering.

The

levels

are

indi-

cated

on

the

panel

as

positive

to

the

right

and

negative

to

the

left.

Negative

positions

of

the

LEVEL

control

cause

triggering

to

occur

dur-

ing

negative

levels

of

the

triggering

waveform

and

positive

positions

cause

triggering

during

positive

levels.

This

control

is

not

used

in

the

AUTOMATIC

and

HF

SYNC

positions

of

the

TRIGGERING

MODE

switch.

Trigger

Slope

The

+

positions

of

the

TRIGGERSLOPE

switch

(black

knob)

cause

triggering

to

occur

during

the

rising

portion

of

the

triggering

waveform.

The

level

may

be

either

negative

or

positive.

The

-

positions

cause

triggering

to

occur

during

the

falling

portion

of

the

waveform.

Thus

for

slow

rising

waveforms

such

as

sine

waves,

the

triggering

point

can

be

caused

to

occur

at

almost

any

point

in

the

waveform.

An

additional

function

of

the

TRIGGERSLOPE

switch

selects

the

source

of

trigger

signals.

For

each

of

the

available

signal

sources,

the

switch

provides

a

choice

of

positive

or

negative

slope.

Triggering

Mode

The

TRIGGERING

MODE

switch

arranges

the

circuits

to

provide

the

kind

of

triggering

you

need.

This

is

the

red

knob

and

the

positions

it

selects

are

labeled

in

red

on

the

panel.

Slowly

changing

waveforms

work

best

on

the

AC

SLOW

and

DC

positions.

In

the

AC

SLOW

position

a

capacitor

removes

the

dc

component

of

the

triggering

waveform

and

makes

triggering

on

the

vertical

signal

independent

of

trace

posi-

a

531/541—-OPERATING

INSTRUCTIONS

MODE

switch

is

primarily

for

signals

having

a

repetition

rate

in

excess

of

ten

megacycles.

In

this

position

the

sweep

will

trigger poorly,

if

at

all,

on

the

calibrator

waveform.

To

trigger

on

a

high-frequency

signal,

simply

advance

the

STABILITY

control

until

a

stable

trace

is

ob-

tained.

The

LEVEL

control

is

not

used

in

this

position.

INSTRUCTIONS

tion.

This

position

is

suitable

for

signals

from

twenty

cycles

up

to

about

five

or

ten

megacycles.

The

DC

position

is

the

same

except

that

it

re-

sponds

to

dc

as

well.

In

the

AC

FAST

position,

the

circuit

includes

an

rc

filter,

useful

for

pre-

venting

60-cycle,

or

other

low-frequency

com-

ponents,

from

triggering

the

sweep

when

both

high-

and

low-frequency

components

are

present

in

the

triggering

waveform.

The

low-frequency

limit

is

about

two

kilocycles.

In

these three

positions,

if

the

STABILITY

control

is

properly

set,

the

sweep

will

not

run

unless

triggered

by

a

signal.

The

AUTOMATIC

and

HF

SYNC

switch

posi-

tions

both

arrange

synchronizing

circuits

rather

than

strictly

triggering

circuits.

The

AUTO-

MATIC

circuit

provides

a

free-running

multi-

vibrator

with

a

normal

repetition

rate

of

about

50

cycles,

which

locks

in

and

runs

synchro-

nously

with

recurrent

triggering

waveforms

from

60

cycles

to

about

2

megacycles.

The

synchronized

multivibrator

then

triggers

the

sweep-gating

multivibrator,

The

HF

SYNC

switch

setting

arranges

a

cir-

cuit

which

connects

the

triggering

source

di-

rectly

to

the

sweep-gating

multivibrator

so

that

it

can

synchronize

with

the

triggering

wave-

form.

The

sweep-gating

multivibrator

must

be

free-running

for

this

type

of

operation.

It

free-

runs

at

advanced

settings

of

the

STABILITY

control.

It

will

synchronize

with

signals

whose

frequencies

are

as

high

as

30

megacycles,

ata

sweep-repetiton:

rate

up

to

200

kilocycles.

Stability

The

STABILITY

control

adjusts

bias

level

on

the

sweep-gating

multivibrator

near

the

level

at

which

it

will

free-run.

Three

principal

settings

of

the

STABILITY

control

are

used,

the

first

setting

is

with

the

control

advanced

to

the

right,

just

past

the

point

where

the

sweep-gating

mul-

tivibrator

free-runs;

second,

retarded

to

the

left

PAGE

2-3