Hp 181a Service manual

OPERATING

AND

SERVICE

MANUAL

|

.

MODEL

181A/AR

OSCILLOSCOPE

i

l l

SERIALS

PREFIXED:840

‘See

Section

VII

for

Instruments

With

Other

Serial

Prefixes

Copyright

HEWLETT-PACKARD

COMPANY/COLORADO

SPRINGS

DIVISION

1947

.1900

GARDEN

OF

THE

GODS

ROAD,

COLORADO

SPRINGS,

COLORADO,

U,

S.

A.

02612-4

-

NN

PRINTED:

APR

1969

Section

I

Tàble

1-1

|

HORIZONTAL

AMPLIFIER

External

Input

Bandwidth:

dc

cpie,

dc

to

5

MHz;

ac

coupled,

5

Hz

to

5

MHz.

`

Deflection

Factor

(sensitivity)

1

v/div,

+5%

on

Xi;

0.

2

v/div

+5%

on

X5;

0.

1

v/div

+5%

on

X10;

vernier

provides

continuous

adjustment

between

ranges.

Dynamic

range

+5

v.

Input

RC:

1

megohm

shunted

by

ABPEeseiuasely

30

pf.

Sweep

Magnifier:

X1,

X5,

X10;

magnified

sweep

|^

accuracy

x5

6b.

|

CALIBRATOR

|

Type:

approximately

1

kHz

square

wave,

less

than

.3

psec

rise

time.

Voltage:

10v

peak-

-to-peak,

+1%.

CATHODE

RAY

TUBE

AND

CONTROLS

Type:

post-

-accelerator

storage

tube;

8.5

kv

ac-

celerating

potential,

aluminized

P31

phosphor.

Graticule:

8

x

10

division

parallax-free

internal

graticule

marked

in

.

95

centimeter

squares.

-

Subdivisions

of

0.2

div

on

major

axes.

Front

panel

recessed

TRACE

ALIGN

alignstrace

with

graticule.

Y

axis

may

be

aligned

to

be

perpen-

dicular

with

X

axis

with

internal

control

for

ac-

curate

rise

time

measurements.

‘Writing

Rate:

Write

mode;

20

cm/msec

Max

write

mode;

1

cm/sec

Erase:

push-button

erasure

takes

approximately

.300

msec,

Brightness:

greater

than

200

foot/lamberts

with

—

entire

screen

faded

positive.

|

Persistence:

continuously

variable

from

less

than

0.

2

second

to

more

than

one

minute,

or

normal

P31

persistence

of

approx

40

usec.

-

Storage

Time(MAX

W)

Mode:

ten

minutes

is

STORE.

mode,

ten

seconds

in

VIEW

mode.

l

Beam

finder:

pressing

FIND

BEAM

control

when

operating

in

any

mode

except

STORE

or

VIEW

ting

of

horizontal

or

vertical

controls.

.

Intensity

Modulation:

approximately

+2

volts,

dc

to

15

MHz,

will

blank

trace

of

normal

intensity.

Input

resistance

is

5100

ohms.

1-0

GENERAL

brings

trace

on

CRT

screen

regardless

of

set-

.

Model

181A/AR

Table

1-1.

Specifications.

OUTPUTS

Four

emitter

follower

outputs

for

mainanddelayed

gates,

main

and

delayed

sweeps.

Maximum

cur-

rent

available

is

t3

ma.

Outputs

will

drive

imped-

į

ances

down

to

1k

ohm

without

distortion.

Active

Components:

all

solid

state

(

no

vacum

tubes

except

CRT).

Environment:

Model

181A/AR

Oscilloscope

with

-

_

plug-ins

operates

within

specifications

over

the

following

ranges:

.

Temperature:

0°-

C

to

455"

C.

;

Humidity:

to

95%

relative

humidity

to

40°

C.

Altitude:

to

15,000

ft.

Vibration:

vibrated

i

in

three

planes

for

15

min

each

with

0.

010

inch

excursion,

10

to

55

Hz.

;

Power:

115

or

230

volts,

210;

50-400

Hz,

100

|

watts

at

normal

line,

convection

cooled,

Dimensions:

cabinet

(overall

dimensions)

8"

(203)

|

wide,

11"

(280)

high,

22-1/2"

(570)

deep.

Rack

DEnenetone

Model

181AR:

,

NOTES:

Eben

—

DIMENSIONS

De

INCHES

AND

{MILAINETERS)

;

EIA

RACK

HEIGHT

(INCLUDING

FILLER

STRIP

“For

ones

NEIGHT

INCLUDING

FEET)

ADO

E

{8}

Yo

A

|

MEAT

|

REAR

APRON

RECESS.

al

H

IM

|

i

t

3

wi

Rii

75

asas)

1493;

|

—Ó

Ll.

o

mene

FA

(4831

—

Ds

a

[BOA

A~IGOG.

Weight:

(without

plug-

zd

Model

181A;

Net,

24

lbs

(10,9

kg);

Shipping,

32

lbs

(14,5

kg).

.

Model

181AR

(rack);

Net,

26

Ibs

(11,8

kg);

Shipping

35

lbs

(15,9

kg).

Accessories

Furnished:

mesh

contrast

filter,

de~

.

tachable

power

cord,

rack

mounting

hardware,

(rack

model

only).

02612-3

a

Model

181A/AR

Section

I

Paragraphs

1-1

to

1-5

SECTION

1

GENERAL

INFORMATION

1-1.

DESCRIPTION.

1-2.

TheModeli81A/AR,

Figure

1-1,

isa

lightweight,

general

purpose,

variable

persistence,

storage

oscil-

loscope

with

plug-in

capability.

The

Model

181A

and

the

Model

181AR

as

shipped

from

the

factory

are

in-

tended

for

bench

use.

The

Model

181AR

may

be

rack

mounted

as

described

in

Section

II.

1-3.

Except

for

the

CRT,

all

active

components

are

solid

state

devices.

The

Model

181A/AR

is

convec-

tion

cooled

and

operates

within

specifications

over

a

temperature

range

of

0°

C

to

+55°

C.

Figure

1-1.

Model

181A

and

181AR

Oscilloscopes

02612-2

1-4.

The

variable

persistence

capability

is

especially

useful

for

viewing

slow-speed

signals.

Adjustment

of

persistence

time

can

provide

viewing

of

a

complete

trace

with

fading

sufficient

to

prevent

interference

with

the

The

display

persistence

can

read-

ily

be

adjusted

to

eliminate

flicker

and

still

provide

high

resolution.

1-5.

The

storage

feature

of

the

hp

Model

181A/AR

canbeusedto

store

single-shot

occurrences

for

later

viewing

or

photographing.

Comparison

of

waveforms

can

be

accomplished

by

storing

several

separate

oc-

currences

and

later

viewing

them

simultaneously.

Section

I

Paragraphs

1-6

to

1-24

1-6.

The

horizontal

amplifier

has

a

direct-coupled

bandwidth

of

dc

to

5

MHz.

The

ac-coupled

bandwidth

is

5

Hz

to

5

MHz.

With

a

dynamic

range

of

+5

volts,

the

amplifier

has

front-panel

selectable

deflection

ranges

of

1

v/div,

0.

2

v/div

and

0.

1

v/div.

A

vernier

controlprovides

continuous

adjustment

between

ranges.

A

magnified

sweep

accuracy

of

+5%

is

maintained

at

-

selectable

magnifications

of

X1,

X5

or

X10;

and

a

front

panel

BNC

connector

permits

the

use

of

external

de-

flection

signals.

The

external

input

has

an

input

im-

pedance

of

1

megohm

shunted

by

approximately

30

pf.

1-7.

A

rear

panel

BNC

connector

is

provided

for

ex-

ternal

control

of

CRT

blanking.

A

signal

of

approxi-

mately

42v

from

de

to

15

MHz

will

blanka

trace

of

normal

intensity.

The

input

resistance

is

5100

ohms.

1-8.

External

outputs

are

provided

through

four

rear

panel

mounted

BNC

connectors

for

coupling

plug-in

derived

signals

to

external

equipment.

Since

these

outputs

are

dependent

upon

the

plug-ins

utilized,

the

‘appropriate

plug-in

Operating

and

Service

Manual

should

be

referred

to

for

identification

of

the

output

signals

available.

The

output

amplifiers

can

supply

3ma,

andwill

drive

impedances

as

low

as

1000

ohms

without

distortion,

1-9.

A

1kHz

square

wave

signal

is

available

at

the

front

panelfor

calibration

purposes.

Its

amplitude

of

10

volts

peak-to-peakis

accurate

to

+1%,

and

it

has

a

rise

time

of

less

than3u

sec.

The

signal

may

be

used

to

adjust

horizontal

and

vertical

deflection

factors

and

to

compensate

divider

probes.

.

1-10.

CATHODE

RAY

TUBE.

‘1-11,

The

Model

181A/AR

uses

an

internal

graticule,

P31

aluminized

phosphor

CRT.

Special

internal

ele-

ments

provide

the

variable

persistence

and

storage

features.

Parallax

observation

error

is

eliminated

by

use

of

the

internalgraticule,

and

a

non-glare

safety

face

plate

is

bonded

to

the

CRT.

1-12.

WARRANTY.

1-13.

This

instrument

is

certified

and

warranted

as

described

on

the

inside

front

cover

of

this

manual.

The

CRT

is

covered

by

a

warranty

separate

from

the

rest

of

the

instrument.

The

CRT

warranty

and

war-

ranty

claim

forms

are

located

at

the

rear

of

this

manual.

Should

the

CRT

fail

within

the

time

specified

on

the

warranty,

contact

your

nearest

hp

Sales/Service

Office,

and

return

the

CRT

with

the

warranty

form

completed.

i

1-14.

ACCESSORIES

FURNISHED.

1-15.

The

standard

Model

181A/AR

Oscilloscope

is

supplied

with

a

mesh

contrast

filter,

and

a

detachable

Model

181A

/AR

power

cord.

Also

included

with

the

Model

181AR

is

a

rack

mounting

kit.

1-16.

ACCESSORIES

AVAILABLE.

1-17.

A

mobile

test

stand

for

the

cabinet

Model

181A

is

available.

The

Model

1118A

Testmobile

provides

adjustable

height,

tilt,and

rotation.

Equipped

with

locking

wheels,

itis

readily

collapsible

for

transport.

Anadapter

assembly,

available

as

hp

Part

No.

01119-

69501,

permits

the

rack

Model

181AR

to

be

mounted

on

the

Model

1119A

Testmobile.

|

1-18.

A

front

panel

cover

of

fiberglass

material,

hp

Model

10166A,

can

beusedto

provide

front

panel

pro-

tection

for the

cabinet

Model

181A,

and

a

cover

for

the

rack

Model

181AR

is

available

as

hp

Part

No.

5060-0437,

1-18,

For

ease

of

calibration

and

maintenance

an

hp

Model

10407A.

Plug-in

Extender

can

be

obtained.

It

provides

for

removal

of

the

plug-ins

from

the

main

frame

and

exposes

components

and

adjustments.

1-20.

Cameras,

probes,

viewing

hoods,

terminations

and

other

accessory

items

are

available

for

special-

izedrequirements.

Informationonthese

andthe

above

described

accessories

may

be

obtainedfrom

hp

Sales/

Service

Offices

listed

in

the

rear

of

this

manual.

1-21.

INSTRUMENT

IDENTIFICATION.

1-22.

Hewlett-Packarduses

atwo-section,

eight-digit

serial

number

to

identify

instruments.

The

first

three

digits

(precedingthe

dash)

are

the

serial

prefix

which

identifies

a

series

of

instruments;

the

last

five

digits

identify

a

particular

instrument

in

the

series.

The

serial

number

appears

on

a

plate

located

on

the

rear

panel.

All

correspondence

with

a

Hewlett-Packard

Sales/Service

Office

inregardto

an

instrument

should

reference

the

complete

serial

number.

1-23.

SCOPE

OF

MANUAL.

1-24.

This

manual

provides

operating

and

service

in-

formation

for

the

hp

Model

181A/AR

Oscilloscope.

Information

and

operation

of

plug-ins

is

contained

in

appropriate

plug-in

manuals.

Information

in

this

manual

applies

directly

to

instruments

(as

manufac-

tured)

with

serial

numbers

prefixed

by

the

three

digits

indicated

on

the

title

page.

If

the

serial

prefix

of

the

instrument

is

different

from

that

on

the

title

page,

a

"Manual

Changes"

sheet

supplied,

or

Section

VII

of

this

manual,

will

describe

changes

which

will

adapt

this

manual

to

provide

correct

coverage.

"Technical

corrections

(if

any)

to

this

manual,

due

to

known

errors

in

print,

are

called

Errata

and

are

shown

on

the

change

sheet.

For

information

on

manual

cover-

age

of

any

hpinstrument,

contact

the

nearest

hp

Sales/

Service

Office

(addresses

are

listed

at

the

rear

of

this

manual).

02612-2

m—-—

UÓ——————

Model

181

A/AR

|.

Section

H

Paragraphs

2-1

to

2-17

SECTION

Hi

INSTALLATION

2-1.

INITIAL

INSPECTION.

2-2.

MECHANICAL

CHECK.

Check

the

shipping

carton

for

damage

immediately

after

receipt.

If

itis

.damaged,

ask

the

carrier's

agent

to

be

present

when

the

instrument

is

unpacked.

Inspect

the

Model

181A/AR

for

physical

damage

such

as

bent

or

broken

parts

and

dents

or

scratches.

If

damage

is

found,

refer

to

Paragraph

2-4

for

recommended

claim

procedure.

H

the

Model

181A/AR

appears

undamaged,

perform

the

electrical

check

(Paragraph

2-3).

Retain

the

pack-

aging

material

for

possible

future

use.

2-3.

ELECTRICAL

CHECK.

The

performance

check

is

given

in

Paragraphs

5-5

through

5-14.

This

check

will

determine

whether

or

not

the

instrumentis

still

operating

within

its

specifications

as

listed

in

Table

1-1.

The

initial

performance

and

accuracy

of

this

instrument

are

certified

as

stated

on

the

inside

front

cover

of

this

manual.

If

the

Model

181A/AR

does

not

operate

as

specified,

refer

to

Paragraph

2-4

for

the

recommended

claim

procedure.

Priortoiniti-

ating

any

performance

check,

refer

to

Paragraphs

2-10

through

2-14

andthe

operating

guidance

provided

in

Section

HI.

2-4.

CLAIMS.

2-5.

H

physical

damage

is

found

or

if

the

instrument

is

not

within

specifications

when

received,

notify

the

carrier

and

the

nearest

Hewlett-Packard

Sales/Service

Office

immediately.

The

Sales/Service

Office

will

arrange

for

the

repair

or

replacement

of

the

instrument

without

waiting

for

a

claim

to

be

settled

with

the

carrier.

2-6,

REPACKAGING

FOR

SHIPMENT.

2-7.

Hf

the

instrument

is

to

be

shipped

to

a

Hewlett-

Packard

Sales/Service

Office,

attach

atagto

it

show-

ing

owner

and

owner's

address,

instrument's

model

number

and

8

digit

serial.number,

and

a

description

of

service

required.

2-8.

The

original

shipping

carton

and

packaging

ma-

terials,

exceptfor

the

accordion-pleated

pads,

should

be

used

for

reshipment..

If

they

are

not

available

or

reusable,

the

instrument

should

be

repackaged

with

the

following

materials:

a.

A

double-walled

carton

(refer

to

Tabie

2-1

for

test

strength

required).

Table

2-1.

Shipping

Carton

Test

Strength

Gross

Weight

(ibs)

Carton

Test

Strength

(lbs)

up

to

10

to

30

to

120

to

140

to

160

02612-3

b.

Heavy

paper

or

sheets

of

cardboard

to

protect

all

instrument

surfaces

(use

a

nonabrasive

material

such

as

polyurethane

or

à

cushioned

paper

such

as.

Kimpak

around

all

projecting

parts).

C.

At

least

4

inches

of

tightly

packed,

industry

approved,

shock

absorbing

material,

such

as

extra

firm

polyurethane

foam.

d.

Heavy

duty

shipping

tape

to

secure

outside

of

carton.

(2-9.

PREPARATION

FOR

USE.

2-10.

POWER

REQUIREMENTS.

2-11.

The

Model

181A/AR

requires

either

a

115

or

230

vac

+10%,

single

phase,

50to

400

Hz

power

source

:

that

can

deliver

100

watts.

a.

115V

OPERATION.

Thisinstrument

as

shipped,

is

ready

for

operation

on

115

vac.

See

Step

b

below

for

230

vac

operation.

Before

applying

power,

check

the

rear

panel

slide

switch

for

proper

position,

(115

or

230).

b.

230V

OPERATION.

If

the

instrument

is

to

be

operated

on

230

vac,

setthe

rear

panel

switch

to

230.

It

is

not

necessary

to

replace

the

115V

fuse.

Position-

ing

the

115/230

switch

selects

the

proper

fuse

forthe

desired

voltage.

2.12.

THREE-CONDUCTOR

POWER

CABLE.

2-13.

The

National

Electrical

Manufacturer's

Associ-

ation

(NEMA)

recommends

that

the

instrument

panel

and

cabinet

be

grounded

to

protect

the

operating

per-

.

sonnel.

The

Model

181A/AR

is

equipped

with

a

de-

tachable

three-conductor

power

cord

which,

when

plugged

into

an

appropriate

outlet,

grounds

the

instru-

ment

through

the

round

offset

pin.

When

operating

the

Model

181A/AR

from

a

two-contact

outlet,

use

a

three-conductor

to

two-conductor

adapter.

Preserve

the

safety

feature

by

grounding

the

adapter

lead.

A

3-way

grounding

terminal

is

also

provided

on

the

rear

panel

of

the

instrument.

2-14.

INSTRUMENT

MOUNTING.

2-15.

BENCH

USE. Both

the

Model

181A

and

the

Model

181AR,

as

shipped

from

the

factory,

are

in-

tended

for

bench

use,

The

Model

181AR,

however,

may

be

rack

mounted

as

described

in

Paragraph

2-16.

RACK

MOUNTING.

A

kit

for

converting

the

Model

181AR

to

a

rack

mount

is

supplied

with

each

instrument.

Instructions

for

making

the

conversion

are

given

below.

Refer

to

Figure

2-1

for

parts

iden-

tification.

2-1

Section

II

Paragraphs

2-18

to

2-22

BOTTOM

PANEL

iras

TILT

STAND

"d

FOOT-BUTTON

PLASTIC

FOOT

TRIM

STRIP

Model

181A/AR

-A

|

ADHESIVE

BACK)

"d

acm

MOUNTING

FLANGE

TOOOHF

-8—19

Figure

2-1.

Bernch/Rack-Mount

Conversion

‘a.

Detach

tilt

stand

by

pressing

itaway

from

front

feet.

Remove

all

plastic

feet

by

depressing

metal

but-

ton

and

sliding

feet

free.

b.

Remove

aluminum

trim

stripfrom

each

side

of

instrument

with

a

thin

blade

tool.

c.

Attach

rack

mounting

flange

in

space

from

which

trim

strip

was

removed

{use

screws

provided

with

kit).

Large

notch

of

flange

should

be

positioned

at

bottom

of

instrument.

2-17.

INSTRUMENT

COOLING.

2-18.

The

Model

181A/AR

does

not

need

forced-air

cooling

when

operated

in

an

amibient

temperature

of

0

to

+55

degrees

centigrade.

Normal

air

circula-

tion

wil

maintain

a

reasonable

temperature

within

the

instrument.

2-19.

CONTRAST

FILTER

AND

BEZEL

REMOVAL.

2-20.

A

contrast

filter

which

also

acts

as

an

RFI

Shield

is

located

behind

the

bezel.

Use

ofthe

filter

is

recommended

since

it

provides

for

comfortable

viewingand

RFI

shielding.

In

specificcases,

however,

such

as

when

a

camera

is

attached

for

use

with

the

oscilloscope,

removal

of

the

filter

may

be

desirable.

To

accomplish

this,

merely

remove

the

bezel

as

shown

in

Figure

2-2,

slip

the

filter

out,

and

replace

the

bezel.

2-21.

To

remove

the

bezel,

grasp

it

as

shown

in

Figure

2~2A,

gently

apply

a

downwardpressure

with

the

index

fingers

until

the

bezel's

upper

ear

is

free

of

its

slot,

pull

slightly

forward

and

release.

Next,

grasp

the

bezel

as

shown

in

Figure

2-2B,

apply

an

upward

pressure

with

the

thumbs

until

the

bezel's

2-2

lower

ear

clears

its

slot,

pull

forward

and

remove

the

bezel.

Be

certain

to

apply

pressure

on

the

inner

edge

of

the

bezel

to

release

the

ears

in

both

steps

since

pressure

on

the

outer

edge

tends

to

cause

a

swivel

action,

defeating

the

purpose,

and

subjecting.

the

ears

to

possible

damage.

Figure

2-2,

Bezel

Removal

02612-3

Model

181A/AR

Section

HI

Paragraphs

3-1

to

3-16

SECTION

Ili

OPERATION

3-1.

INTRODUCTION.

3-2.

The

Model

181A/AR

is

a

light

weight,

variable

persistence,

storage

oscilloscope

using

plug-in

vertical

-andhorizontal

modules.

Both

highand

low

voltage

pow-

er

supplies,

a

calibrator,

the

CRT,

and

circuitry

for

the

variable

persistence

and

storage

operationare

con-

tained

in

the

Model

181A/AR.

A

compartment

for

the

horizontal

and

vertical

plug-ins

is

locatedinthe

lower

portion

of

the

Model

181A

and

in

the

right

hand

portion

of

the

Model

181AR.

In

both

models

the

compartment

is

designed

to

accept

the

vertical

plug-in

on

the

left

side

and

the

horizontal

plug-in

on

the

right.

The

plug-

in

units

must

be

locked

together

before

being

inserted

into

the

compartment(see

plug-in

manuals).

3-3.

OPERATING

CONSIDERATIONS.

3-4.

Prior

to

operating

the

Model

181A/AR,

the

oper-

ator

must

have

a

thorough

understanding

of

instrument

operation

and

control

functions.

This

section

should

be

readinits

entirety

before

attempting

to

operate

the

instrument.

To

avoid

CRT

damage,

the

following

pro-

cedure

should

be

followed

every

time

the

instrument

is

operated.

3-5.

The

following

are

steps

that

must

betakenprior

toapplying

power

tothe

Model

181A/AR

Oscilloscope.

-a.

Depress

WRITE

push

button.

pb.

Set

PERSISTENCE

control

fully

ecw.

c.

Set

INTENSITY

control

fully

cew.

d.

Apply

power

to

Model

181A/AR

e.

After

3

minutes,

the

entire

CRT

viewing

area

should

be

evenly

flooded

green.

l

NOTE

If

there

is

no

green

illumination,

turn

instrument

off

and

check

all

CRT

con-

nections.

.

3-6.

CONTROLS

AND

CONNECTORS.

3-7.

The

location

of

operating

controis

andconnectors

is

shown

in

Figure

3-1

together

witha

brief

explanation

of

their

functions.

Additionai

information

regarding

some

of

these

controls

and

connectors

is

provided

below.

3.8.

FRONT

PANEL.

3-9.

FOCUS

AND

ASTIGMATISM.

These

controls

are

providedtoassure

uniform

focus

of

the

trace

over

the

entire

CRT

screen.

To

adjust,

set

the

Presentation

Selector

to

WRITE,

center

a

low-intensity

spot

on

the

CRT

screen,

and

adjust

FOCUS

and

ASTIGMATISM

02612-2

controls

for

a

small,

round,

sharply

focused

spot.

Readjustment

of

the

ASTIGMATISM

controlis

seldom

required

except,

for

example,

when

the

vertical

plug-

in

is

changed.

3-10.

STORE.

In

order

to

retain

whatever

is

visible

on

the

CRT,

depressthe

STORE

push

button.

The

sig-

nal

will

be

stored

at

reduced

intensity,

resulting

in

a

storage

time

of

greater

than

one

hour.

The

INTENSITY,

PERSISTENCE,

FOCUS,

ERASE,

and

HORIZONTAL

POSITION

controls

do

not

affectthe

presentation

in

the

STORE

mode.

3-11.

In

some

applications,

it

may

be

desirableto

show

several

overlapping

traces

at

once.

This

is

possible

through

proper

manipulation

of

the

PERSISTENCE

and

INTENSITY

controls.

Simply

obtainthe

desired

mul-

tiple

trace

display

in

the

WRITE

mode,

then

depress

the

STORE

push

button.

3-12.

A

display

stored

on

the

CRT

when

power

is

re-

moved

from

the

instrument

will

remain

stored

for

Severaldays.

In

order

to

observethis

stored

display,

depress

the

VIEW

push

button

and

turn

the

POSITION

control

on

the

Vertical

Plug-in

counterclockwise

prior

to

restoring

power

to

the

instrument.

This

prevents

a

bright

spot

from

being

portrayed

on

the

screen

due

to

the

initial

surge

from

the

CRT

write

gun.

.

3-13.

Several

individual

waveforms

may

also

be

stored,

eventhoughtheyare

writtenatdifferenttimes.

Having

storedatrace,

for

instance,

the

operator

may

choose

to

switch

backto

WRITE

andrecordanothertrace,

etc.,

prior

to

erasing.

And

by

turning

the

Model

181A/AR

power

off,

as

few

as

one

trace

a

day

can

be

recorded

fora

weekor

more,

dependingontotaltime

instrument

is

turned

on,

as

storage

time

would

decrease

accord-

ingly.

3-14.

VIEW.

To

observe

a

previously

stored

display,

depress

the

VIEW

push

button.

The

stored

display

will

be

intensified

to

a

brightness

level

determined

by

the

intensity

and

persistence

values

selected

during

the

writeprocess.

Again,

theINTENSITY,

PERSISTENCE,

FOCUS,

ERASE

and

POSITION

controls

do

not

affect

the

display.

Excessive

intensity

for

long

duration

may

damage

the

CRT

storage

mesh.

The

INTENSITY

setting

for

any

sweep

speed

should

be

minimum

usable

in-

tensity.

3-15.

NORMAL,

Selection

of

this

operating

mode

dis-

ables

the

variable

persistence

and

storage

features

of

the

instrument.

Itwillnowfunctionasa

conventional,

general

purpose,

oscilloscope.

The

PERSISTENCE

control

does

not

function

in

this

mode.

Always

adjust

INTENSITY

in

WRITE

mode

with

minimum

PERSIS-

TENCE,

then

switch

to

NORMAL.

3-16.

WRITE.

Depressing

the

WRITE

push

button

3-1

Section

HI

Figure

3-1

Note:

1,

FOCUS:

Controls

sharpness

of

writing

beam.

2.

STORE:

Retains

displayed

signal

at

reduced

intensity

for

long

time

storage.

3.

VIEW:

Intensifies

stored

display

to

brightness

‘level

for

viewing.

4.

NORMAL:

Selects

operation

as

standard

oscil-

loscope.

5.

WRITE:

Operates

CRT

at

normal

writing

rate

with

variable

persistence.

6.

MAX

WRITE:

Operates

CRT

at

maximum

writing

rate

with

variable

persistence.

ERASE:

Removes

stored

or

written

displays.

8.

PERSISTENCE:

Controls

endurance

time

of

.

displayed

signal.

9.

ASTIGMATISM:

Adjust

roundness

of

writing

beam.

10.

TRACE

ALIGN:

Rotates

trace

around

center

of

CRT

face.

11.

FIND

BEAM:

Returns

display

to

CRT.

12.

INTENSITY:

Controls

brightness

of

display.

13.

POSITION:

Coarse

adjustment

of

display's

horizontal

position.

14.

FINE:

Fine

adjustment

of

display's

horizontal

position,

l

15.

MAGNIFIER:

Magnifies

horizontal

display.

16.

PHASE/BANDWIDTH:

Selects

between

nor-

mal

operation

(BANDWIDTH)

and

XY

opera-

tion

(PHASE).

Located

inside

on

board.

Figure

3-1.

3-2

roo

om

H.

18.

19.

20.

21.

K.

Model

181A/AR

Xo.

0

OCC

HA:

BIA-

A-

11A

Models181A

and

181AR

differ

only

in

power

module

location.

Allcontrolsare

identical.

See

Fig.

1-1.

DISPLAY:

Selects

source

of

horizontal

input

signal.

AC/DC:

Selects

AC

or

DC

coupling

of

an

ex-

ternal

horizontal

input

signal.

—

EXT

INPUT:

BNC

connector

for

coupling

an

external

horizontal

input

signal

to

oscilloscope.

POWER:

Push-button

switch

with

indicator

light

for

turning

oscilloscope

on

and

off.

CALIBRATOR:

Provides

a

1~kKHz

square

wave

signal

at

10v

pk-pk.

l

REAR

PANEL

AC

INPUT:

3-wire

ac

power

line

input

jack,

MAIN

GATE

OUTPUT:

BNC

for

connecting

main

gate

to

external

equipment,

DELAYED

GATE

OUTPUT:

BNC

for

connect-

ing

delayed

gate

to

external

equipment.

DELAYED

SWEEP

OUTPUT:

BNC

for

con-

necting

delayed

sweep

to

external

equipment.

MAIN

SWEEP

OUTPUT:

BNC

for

connecting

main

sweep

to

external

equipment,

Z-AXIS INPUT:

BNC

for

connecting

external

intensification

or

blanking

signal.

FUSE:

AC

line

fuse

for

230vac

operation.

FUSE:

AC

line

fuse

for

115vac

operation.

LINE

SWITCH:

Input

power

switch

for

selec-

tion

of

115vac

or

230vac

operation.

GROUNDING

CONNECTOR:

3-way

connector

jack

for

instrument

grounding.

Front

and

Rear

Panel

Controls

and

Connectors.

02612-2

Model

181A/AR

establishes

the

CRT

in

a

condition

for

variable

per-

sistence

display

of

a

signal

which

can

later

be

stored.

Use

the

minimum

INTENSITY

and

maximum

PERSIS-

TENCE

required

to

obtain

the

desired

display.

3-171.

MAX

WRITE.

Operation

in

the

Max

Write

mode

(MAX

W.)

provides

a

more

rapid

build-up

and

display

of

fast

single-shot

signals.

Since

the

background

il-

lumination

also

increases

more

rapidly,

the

CRT

con-

trast

level

and

storage

time

are

reduced.

3-18.

ERASE.

Depressingthe

ERASE

push

button

will

remove

stored

signals

from

the

CRT

when

either

the

WRITE

or

MAX

W

push

buttonisdepressed.

Stored

or

written

displays

that

remain

visible

after

erasure,

may

require

the

ERASE

push-button

be

held

depress-

ed

for

approximately

30

seconds.

3-19.

PERSISTENCE

ANDINTENSITY.

These

controls

determine

the

viewing

time

of

a

signal

being

displayed.

The

INTENSITY

sets

the

brightness

of

the

trace

as

it

is

written.

The

PERSISTENCE

control

is

used

to

establishthe

desired

duration

of

signal

viewing

without

rewriting.

Itaccomplishes

this

by

varying

the

rate

at

.

Which

the

displayed

signal

is

erased.

3-20.

TRACE

ALIGN.

The

TRACE

ALIGN

adjustment

controlcompensatesífor

external

magnetic

fields

that

may

affect

the

alignment

of

the

horizontal

trace

with

the

graticule.

Thealignment

should

be

checked

when

the

instrument

is

moved

to

a

new

location

and

the

ad-

justment

made

whenever

necessary.

3-21.

FIND

BEAM.

Off-screen

positioning

of

the

CRT

beam

may

occur

due

to

initial

improper

control

set-

tings

or

a

very

high

dc

input

signal.

The

beam

may

be

brought

back

on

screen

by

depressing

the

FIND

BEAM

push

button.

Adjustthe

horizontaland

vertical

position

controls

to

center

the

beam

(refer

to

the

plug-

in

manuals).

Adjust

the

INTENSITY

controlto

obtain

a

visible

trace.

.

9-22.

MAGNIFIER,

Whenthe

DISPLAY

control

is

set

to

EXT

CAL,

the

MAGNIFIER

provides

switched

gain

levels

in

the

horizontal

amplifier

of

X1, X5,

or

X10.

In

the

X5

or

X10

positions,

the

horizontal

gain

is

in-

creased

to

provide

an

amplified

display

of

five

or

ten

times,

respectively.

Theinsertion

ofa

1v

signal

into

the

EXT

INPUT

jack

will

result

ina

1-division

deflec-

tionin

X1,

5-division

in

X5,

anda

10-division

deflec-

tion

in

the

X10

position.

8-23.

DISPLAY.

This

control

determines

the

input

signaltothe

horizontalamplifier.

With

the

DISPLAY

controlsetto

EXT

CAL,

the

external

horizontal

input

signal

is

coupled

directly

to

the

horizontal

amplifier.

As

the

DISPLAY

control

is

rotated

counterclockwise,

the

external

signal

is

increasingly

attenuated.

When

the

DISPLAY

control

is

fully

counterclockwise

(INT),

the

externalinputsignalis

disconnectedandthe

inter-

nal

sweep

is

coupled

directly

to

the

horizontal

ampli-

fier.

3-24.

CALIBRATOR.

The

1

kHz

square-wave

calibrator

output

signal

of

10v

can

beused

for

vertical

sensitivity

calibration

and

for

probe

compensationadjustment.

The

CALIBRATOR

output

amplitude

is

accurate

within:

1%.

Rise

time

of

the

square-wave

output

is

less

than

3

u

sec.

02612-2

Section

IH

Paragraphs

3-17

to

3-37

3-25.

REAR

PANEL.

3-26.

OUTPUTS.

Main

and

delayed

sweep

and

gate

signals

are

available

at

rear

panel

BNC

connectors

of

the

Model

181A/AR.

These

outputs

are

providedfrom

separate

isolationamplifiers

which

can

supply

3

ma

and

will

drive

impedances

as

low

as

1000

ohms

without

distortion.

The

plug-ins

used

in

the

Model

181A/AR

and

the

control

settings

employed

deter

mine

the

out-

put

signals

available.

3-27.

Z-AXIS

INPUT.

Anexternal

signal

can

be

util-

-

izedfor

control

of

CRT

intensity.

A

rear~panel

mounted

BNC

connector

permits

a

direct

connectionto

the

CRT

intensity

gate

amplifier.

A

signal

of

approximately

42v,

dcto

15

MHz,

isrequired

to

blank

a

beam

of

nor-

mal

intensity.

Input

of

a

negative

signal

c

can

be

used

for

beam

intensification.

3-28.

AC

LINE

INPUT.

A

three-conductor

ac

input

jack

is

providedfor

power

input.

Also

located

on

the

rear

panelis

the

115/230v

slide

switch

andthe

required

fuses

for

115

vac

and

230

vac

operation.

3-29.

INTERNAL.

3-30.

PHASE/BANDWIDTH.

'TheModel181A/AR

can

also

be

usedfor

phase

measurements.

Positioning

the

.PHASE/BANDWIDTH

switch

to

PHASE

causes

the

horizontal

input

signal

to

be

delayedthe

same

amount

of

time

as

the

vertical

input

signal.

NOTE

Make

certain

the

control

is

returned

to

the

Bandwidth

position

after

making

phase

measurements.

i

3-31.

PLUG-IN

UNITS.

3-32.

The

Model

181A/AR

Oscilloscope

requires

hori-

zontaland

vertical

plug-ins.

The

deflection

sensitivity

of

the

CRT

may

vary

slightly

with

differentunits.

Plug-

in

units

should

be

calibrated

when

first

installed

or

when

shifted

between

oscilloscopes.

The

horizontal

and

vertical

plug-in

units

must

be

locked

together

prior

to

insertion

into

the

Model

181A/AR

mainframe.

Con-

sult

the

respective

plug-in

Operating

andService

Man-

ual

for

operation

and

capability

information.

3-33.

MAGNETIC

INTERFERENCE.

3-34.

The

CRT

is

provided

witha

mu-

metal

shield

for

protection

against

magnetic

fields.

Duetothe

sensi-

tivity

ofthe

CRT,

it

is

possible

that

the

strong

magnetic

fieldfrom

nearby

motors,

ac

linetransformers,

etc.,

may

still

result

in

a

noticeable

beam

deflection)

In

this

event,

reorient

or

relocate

the

instrument

with

respect

to

the

interfering

device.

l

3-35.

OPERATING

CONDITIONS.

3-36.

DEFINITIONS.

3-37.

Several

words

and

phrases,

the

definition

of.

which

may

vary

slightly

from

common

usage,

are

used

3-3

Section

II

Paragraphs

3-38

to

3-43

to

describe

the

operation

of

the

Model

181A/AR.

The

.

definitions

ofthese

words

and

phrases

which

apply

to

_the

Model

181A/AR

are

as

follows:

a.

WRITE-To

transform

an

input

signal

into

a

visible

display

on

the

CRT

screen.

b.

PERSISTENCE-The

iength

of

time

a

single

Sweep

written

display

remains

visible

on

the

CRT

Screen

(INTENSITY

and

sweep

time

constant).

c.

STORE-To

retain,

at

reducedintensity,

a

dis-

piay

which

has

been

written

on

the

CRT.

d.

VIEW-To

redisplay

onthe

CRT

screen,

at

nor-

mal

intensity,

a

stored

display.

e.

ERASE-

To

remove

all

displays,

and

blooms

which

have

been

stored,

or

written

with

persistence

on

the

CRT.

f.

INTENSITY-The

brightness

of

a

display

as

it

is

written

on

the

CRT

sereen

(

PERSISTENCE

and

Sweep

Time

Constant).

g.

BLOOM-A

visible,

non-symmetrical

expan-

sion

of

a

display

written

on

the

CRT

screen.

LIB

EAT

A

I2]

Figure

3-2.

Fade

Positive

and

BackgroundIllumination.

3-4

Model

181A/AR

h.

FADE

POSITIVE-Display

obscured

by

slow

blooming,

see

Figure

3-2A.

i

BACKGROUND

ILLUMINATION-A

green

cloud

of

illumination

visible

on

the

CRT

screen,

see

Figure

3-2B.

j

SWEEP

TIME-The

time

(inseconds,

millisec-

onds,

or

microseconds)

required

for

the

beam

to

move

horizontally

one

unit

of

distance

across

the

CRT

screen,

when

writing

a

display.

3.38.

CONTROL

FUNCTIONS.

3-39.

PERSISTENCE

ANDINTENSITY.

These

controls

contribute

to

the

duration

of

afterglow

ofadisplay.

The

PERSISTENCE

control

sets

the

rate

at

which

a

display

is

erased;

INTENSITY

sets

the

brightness

of

the

trace

as

it

is

written.

With

a

given

PERSISTENCE

setting,

the

actual

duration

of

trace

afterglow

may

be

increased

by

increasing

the

INTENSITY.

Since

the

PERSISTENCE

control

sets

the

rate

of

erasing

a

written

display,

it

follows

that

a

brighter

trace

will

require

more

time

to

be

erased.

Conversely,

a

display

of

low

intensity

.

wil

disappear

more

rapidly.

The

same

principle

applies

to

a

stored

display

of

high

and

low

intensity.

The

storage

mesh

of

the

CRT

is

not

easily

damaged,

however,

a

high-

intensity

repetitive

trace

or

spot,

writ-

ten

on

the

screen

for

an

extended

time,

may

not

erase

completely.

To

prevent

CRT

damage,

use

minimum

INTENSITY

which

will

give

the

desired

display

for

a

given

PERSISTENCE

setting.

3-40.

PRESENTATION

SELECTION,

Push

button

controls

select

the

mode

in.which

the

CRT

functions,

With

ERASE

push

button

depressed,

the

other

three

functions

are

disconnectedandall

stored

and

persist-

ing

displays

are

removed

from

the

CRT.

The

WRITE

and

MAX

W.

modes

are

the

only

conditions

in

which

a

display

may

be

written

on

the

CRT

screen.

The

STORE

mode

disconnects

the

WRITE

and

ERASE

func-

tions

and

retains

written

displays

(at

reduced

intens-

ity)

on

the

CRT.

INTENSITY,

PERSISTENCE,

and

ERASE

do

not

function

in

the

STORE

mode.

The

VIEW

mode

intensifies

the

stored

dispiay

to

a

set

brightness

and

again,

INTENSITY,

PERSISTENCE,

and

ERASE

do

not

affect

the

display.

3-41.

MAX

WRITE.

When

MAX

W.

push

buttonis

de-

pressedandthen

the

ERASE

push

button

is

depressed

and

released,

the

storage

surface

is

erased

and

then

primed

(or

pre-fogged)

to

allow

much

faster

writing

on

the

storage

surface.

The

display,

however,

has

reduced

contrast

and

fades

positive

more

rapidly.

The

contrast

and

storage

time

are

also

reduced

in

this

mode.

3-42.

OPERATING

TIPS.

3-43.

This

information

is

provided

toaidthe

operator

in

becoming

familiar

with

the

Model

181A/AR

controls

andtheir

functions,

andtoserveas

a

guide

for

obtain-

ing

the

desired

CRT

display.

a.

For

normal

persistence

operation,

depress

WRITE

push

button

and

turn

PERSISTENCE

control

02612-3

Model

181A/AR

fully

ecw.

Slowly

rotate

INTENSITY

control

cw

to

a

point

where

no

trace

blooming

appears.

Depress

NORMAL

push

button;

do

not

increase.

INTENSITY

while

in

NORMAL.

H

sweepspeedis

changed,

always

check

for

proper

intensity

using

the

above

procedure.

When

not

actively

using

the

oscilloscope,

switch

to

STORE

or

VIEW

mode,

thus

.

turning

off

the

write

gun

and

eliminating

the

possibility

of

burningthe

storage

mesh.

Whenin

WRITE,

NORM,

or

MAX

W

mode,

any

visible

trace

may

cause

permanent

damage

to

the

CRT

if

display

is

left

for

prolonged

periods

oftime.

Topreventthis

from

happening,

periodically

erasethe

dis-

play

or

switch

to

STORE

mode

if

you

wish

to

retain

the

image.

b.

For

variable

persistence

operation,

press

the

WRITE

push

button.

Use

minimum

INTENSITY

and

maximum

PERSISTENCE

compatible

with

display.

c.

UseMAX

WRITE

mode

only

for

fast

sweeptime,

single

shot

display,

or

to

improve

the

uniformity

of

trace

intensity.

The

MAX

W,

mode

causes

more

rapid

positive

fading

onthe

CRT

and

persistence

or

storage

time

of

the

display

is

thus

reduced.

d.

To

store

a

display,

pressthe

WRITE

push

but-

ton,

adjustthe

INTENSITY

and

PERSISTENCE

for

the

desired

display,

and

press

the

STORE

push

button.

e.

Toviewastoreddisplay,

press

thé

VIEW

push

button.

f.

Tostore

more

than

one

display,

press

the

WRITE

push

button,

set

PERSISTENCE

fully

clockwise

and

INTENSITY

as

required;

allow

first

display

to

be

writ-

tenontheC

RT.

Set

INTENSITY

fully

counterclockwise

andconnect

the

second

signaltobe

stored.

Reset

ver-

tical

POSITION

if

second

display

is

not

to

be

super-

imposed

onfirst.

Slowly

rotate

INTENSITY

clockwise

until

second

display

appears.

Press

theSTORE

push

button.

g.

A

display

which

is

stored

when

the

Model

181

A/AR

power

is

turned

off

will

remain

stored

for

sev-

eral

days.

To

redisplay

the

stored

waveform,

press

the

STORE

pushbutton,

turn

POSITION

controls

fully

cew

before

turning

power

on.

Apply

power

to

Model

181A/ARandallow

5

minute

warm-up.

If

stored

sig-

02612-4

‘Section

HI

Paragraphs

3-44

to

3-47

nal

was

written

in

WRITE

mode,

depress

WRITE

pushbutton.

Ifstored

in

MAX

W

mode,

depress

MAX

W

pushbutton.

Depress

VIEW

pushbutton

to

observe

waveform.

h.

To

eraseall

persistent

or

stored

displays,

set

modetoWRITE

(

or

Max

Write

)

and

then

the

ERASE

push

button

for

approximately

2

seconds,

thenrelease.

i.

If

only

a

portion

of

a

slow

sweep

display

is

de-

sired,

press

the

STORE

push

button

when

the

trace

has

been

writtentothe

desired

point;

the

write

gun

is

blanked

and

the

written

portion

is

stored.

j.

Use

a

viewing

hood,

if

desired,

to

improve

sereen-display

contrast.

3-44.

SINGLE-SHOT

OPERATION.

3-45.

To

write

or

store

single-shot

phenomena,

a

trial

setting

of

INTENSITY

is

the

best

approach.

The

amp-

litude

of

the

phenomena

and

the

sweep-time

required

todisplay

itwillaffectthe

persistence.

For

example,

with

maximum

PERSISTENCE

and

some

settings

of

INTENSITY,

a

single-shot

straight-line

may

bloom.

A

single-shot

signal

withamplitude

variations

may

not

cause

bloom.

To

determine

the

best

INTENSITY.

set

ting,

connect

a

signal

which

approximates

the

sweep

time

andamplitude

of

the

single-shot

signalto

be

writ-

ten,

Set

PERSISTENCE

fully

clockwise

and

trigger

a

single

sweep

ofthe

test

signal.

Set

the

INTENSITY

as

far

as

possible

without

causing

blooming.

Repeat

this

procedure,

varying

the

INTENSITY,

until

the

proper

display

is

obtained.

This

setup

should

give

maximum

persistence

to

the

single-shot

display.

After

the

sig-

nal

has

been

written,

press

the

STORE

push

button

to

retain

the

display.

3-46.

Single-shot

signals

which

require

a

sweep

time

faster

than

20

microseconds

per

division

can

be

writ-

ten

with

more

brightness

by

switching

tothe

Max

Write

mode.

The

screen

will

be

unevenly

illuminated

after

erasing

when

in

Max

Write,

Figure

3-2B;

however,

IN-

TENSITY

can

be

set

high

enough

to

make

the

display

vis-

ible

throughthe

illumination.

A

display

writtenin

Max

Write

will

be

more

rapidly

obscured

by

positive

fading

than

a

signal

written

in

NORMAL.

3-47,

Single-shot

signals

which

require

a

sweep

time

between

200

and

20

microseconds

per

division

may

have

low

brightness

at

the

center

of

the

screen.

Fire

a

single-shot

test

signal

with

INTENSITY

and

PERSIST-

ENCE

fully

clockwise

and

press

the

WRITE

push

but-

ton.

If

center

screen

brightness

is

low,

wait

for

one

to

three

minutes

for

the

low

brightness

areato

become

brighter.

Likewise,

if

the

entire

display

brightness

appears

below

a

usable

level,

or

the

display

is

not

visible

at

all,

waitforonetofive

minutes

for

the

dis-

play

to

appear.

3-5

Model

181A/AR

Section

IV

Paragraphs

4-1to

4-11

|

SECTION

IV

PRINCIPLES

OF

OPERATION

4-1.

INTRODUCTION.

4-2.

This

section

provides

circuit

theory

analysis

of

the

Model

181A/AROscilloscope.

Since

variable

per-

sistence

and

storage

techniques

may

be

somewhat

un-

familiar

to

the

reader,

basic

theory

of

operation

will

be

explained

first

to

aid

in

grasping

these

concepts.

An

over-all

block

diagram

is

explained

next,

followed

by

a

detailed

description

of

the

individual

circuits.

4-3.

VAR

PERSISTENCE

&

STORAGE.

4-4.

STORAGE

PRINCIPLES.

4-5.

The

Model

181A/AR

Storage

CRT

consists

mainly

of

a

conventional

electron

gun

with

deflection

plates

(write

gun),

an

aluminized

phosphor

viewing

screen,

a

pair

of

flood

guns

operated

in

parallel,

flood

beam

shaping

and

accelerating

grids,

aflood

beam

collima-

tor,

a

collector

mesh,

and

a

storage

mesh

as

shown

in

Figure

4-1.

`

4-6.

The

write

gun

functions

as

a

conventional

elec-

trostatic

deflection

gun,

delivering

high

velocity

elec-

trons

to

selected

points

on

the

phosphor

viewing

screen.

The

elements

which

provide

storage

and

variable

per-

sistence

are

located

between

the

write

gun

andthe

phos-

phor.

4-1.

The

flood

guns

are

physically

located

just

out-

side

the

horizontal

deflection

plates.

A

cloud

of

elec-

trons

is

emitted

by

each

flood

gun

cathode.

These

clouds

are

combined,

shaped,

and

accelerated

by

two

control

grids.

It

shouldbe

noted

that

under

certain

con-

ditions

the

twoelectronclouds

will

appear

as

light

areas

onthe

viewing

screen

when

the

instrument

is

first

turned

on.

The

combinedcloud

is

further

shapedandacceler-

ated

by

the

collimator

(

a

coating

on

the

inside

of

the

-funnel section

of

the

glass).

The

positive

voltage

on

the

collimator

is

adjusted

so

that

the

flood-gun

elec-

tron

cloud

just

fills

the

CRT

viewing

screen.

The

cloud

is

further

accelerated

toward

the

storage

mesh

and

viewing

screen

by

the

collector

mesh.

After

pas-

sing

through

the

collector

mesh,

the

flood

electrons

are

further

controlled

by

potentials

on

the

storage

mesh

and

suríace.

l

POST

ACCELERATOR

STORAGE

FLOOD

GUNS

MESH

PHOSPHOR

VIEWING

SCREEN

DNE

o

WRITE

GUN’

.

^,

AQUADAG

COLLIMATOR

STORAGE

COLLECTOR

SURFACE

MESH

`

18i

A?

Figure

4-1.

Simplified

CRT

Construction.

02612-2

4-8.

The

storage

mesh

is

located

between

the

collector

meshandthe

phosphor.

The

back

side

of

this

meshis

coated

with

a

layer

of

non-conductive

material.

The

storage

of

information

takes

place

on

the

surface

of

this

non-conductive

material

(storage

surface).

4-0,

The

basis

for

storage

of

information

onthe

non-

conductive

material

is

the

secondary

emission

ratio

curve

shown

in

Figure

4-2.

Thiscurve

shows

the

ratio

of

the

number

of

electrons

leaving

the

surface

to

the

„energy

of

the

electrons

striking

the

surface.

At

an

energy

of

about

40

electron/voits

(ev)

the

number

of

electrons

leaving

the

surface

is

equal

to

the

number

arriving.

The

point

where

the

secondary

emission

ratio

is

equal

to

unity

is

called

"first

crossover."

If

the

surface

is

bombarded

with

electrons

with

more

than

40

ev

of

energy,

the

surface

potential

rises

because

more

electrons

are

leavingthanarriving.

If

the

sur-

face

is

bombarded

with

electrons

with

less

than

40ev

of

energy,

the

surface

potential

decreases

because

fewer

electrons

are

leaving

than

arriving.

e

E-

d

x

=

e

=

iad

>

a

«x

e

Zz

o

id

qi

41440

|

STORAGE

MESH

POTENTIAL

IN

VOLTS

EISE

IBIA--A-

8

|

Figure

4-2.

Secondary

Emission

Ratio.

4-10.

When

the

ERASE

push

button

is

pressed,

the

storage

mesh

is

changed

to

the

same

potential

as

the

collector

mesh

(+156v).

The

storage

surface

is

also

changed

to

nearly

this

same

potential

by

capacitive

coupling.

Since

the

surface

is

then

being

bombarded

by

electrons

with

energies

much

higher

than

first

cross-

over

energy,

the

entire

storage

potential

becomes

equal

to

+156

volts.

The

surface

potential

cannot

in-

crease

beyond

+156

volts

because

the

collector

mesh

would

then

repel

the

emitted

electrons

back

to

the

storage

surface,

tending

to

decrease

the

surface

po-

tential.

l

4-11.

When

the

ERASE

push

button

is

released,

(see

Figure

4-3)

the

storage

mesh

is

now

changed

to

«3.

3

volts

and

the

storage

surface

follows

to

the

same

po-

tential

by

capacitive

coupling.

The

surface

potential

4-1

Section

IV

Paragraphs

4-12

to

4-16

then

decays

to

zero

volts

by

action

of

the

flood

gun

electrons

(surface

below

first

crossover,

brought

to

flood

gun

cathode

potential).

After

100

milliseconds,

the

storage

mesh

is

raised

to

+13.3

volts

and

held

there

for

200

milliseconds.

The

storage

surface

fol-

lows

to

+10

volts

by

capacitive

coupling,

but

immedi-

ately

starts

decaying

toward

zero

volts

by

capturing

flood

gun

electrons.

Atthe

end

of

the

200

milliseconds,

the

storage

mesh

is

brought

back

to

+3.3

volts.

The

storage

surface

is

consequently.

reduced

from

zero

volts

to

-10

volts

by

capacitive

coupling.

4-12.

Since

the

write

gun

electrons

reach

the

storage

surface

withenergy

much

higher

than

first

crossover

energy,

they

charge

the

surface

in

a

positive

direc-

tion

wherever

they

strike.

This

charge

pattern

on

the

storage

surface

remains

for

a

considerable

length

of

time

since

the

storage

material

is

a

very

good

insula-

tor.

4-13.

Those

areas

of

the

storage

surface

which

are

charged

to

near

zero

volts

allow

the

field

created

by

the

high

positive

potential

on

the

post

accelerator

to

"reach

through"

and

capture

flood

gun

electrons,

ac-

celerating

them

to

strike

the

phosphor

viewing

screen,

thereby

causing

the

phosphor

to

emit

light.

Thusthe

pattern

of

charge

on

the

storage

surface

is

made

vis-

ible.

:

4-14.

The

secondary

electrons

emitted

by

the

storage

surface

where

the

write

gun

electrons

strike

must

charge

the

surface

from

its

erased

potential

to

about

-9

volts

before

floodelectrons

can

be

captured

by

the

RELEASE

ERASE

+

i56v

4+152e7V

*l42.7V

Model

181A/AR

post

accelerator.

Thus

the

writing

speed

of

the

CRT

could

be

enhanced

by

erasing

the

surface

to

just

below

this

"cutoff"

level.

Thisis

whatthe

MAX

WRITE

mode

does.

The

disadvantages

of

operating

inthis

mode

are

reduced

storage

time

and

reducedcontrast

ratio.

The

“cutoff

potentials

of

various

areas

of

the

storage

sur-

face

may

not

be

exactly

the

same.

Thus,

the

back-

.

ground

illumination

may

not

be

uniform

when

the

storage

Surface

is

erased

in

the

MAX

WRITE

mode.

4-15.

VARIABLE

PERSISTENCE.

4-16.

Figure

4-4

represents

the

method

of

obtaining

variable

persistence.

The

unwritten

storage

surface

after

erasure

is

at

approximately

-10

volts.

Those

areas

of

the

storage

surface

which

are

struck

by

elec-

trons

from

the

write

gun

become

charged

to

near

zero

volts.

A

+10

volt

pulse

applied

to

the

storage

mesh

moves

the

unwritten

areas

of

the

storage

surface

to

near

zero

voltsandthe

writtenareastonear+10

volts.

While

at

this

potential,

the

written

areas

of

the

stor-

age

surface

attract

and

capture

flood

gun

electrons,

whichtends

to

lower

the

potential

of

these

areas.

When

the

storage

mesh

returns

toits

normal

level,

the

stor-

age

surface

drops

10

volts.

The

unwritien

areas

of

the

storage

surface

return

to

a

-10

volt

potentialand

the

written

areas

return

to

a

slightly

negative

poten-

tial,

somewhat

lower

(more

negative)

than

their

ini-

tial

value.

This

decrease

in

potential

reduces

the

ability

of

the

post

accelerator

potential

to

reach

through

and

capture

flood

electrons,

thus

reducing

the

trace

brightness

slightly.

STORAGE

MESH

POTENTIAL.

STORAGE

SURFACE

P

POTENTIAL

ESEE

MEN

IBIA=

B-S

Figure

4-3.

Storage

Mesh

and

Surface

Potentials

During

Erasure.

4-2

02612-1

Model

181A/AR

4-17.

If

this

procedure

is

repeated

many

times,

the

Stored

trace

will

eventually

be

erased.

The

time

re-

quired

to

accomplish

this

erasure

is

controlled

by

varying

the

duty

cycle

of

the

pulses

applied

to

the

stor-

age

mesh

(or

by

varying

the

pulse

width

if

the

pulse

repetition

rate

remains

fixed).

l l

4-18,

Duringthetime

the

storage

mesh

is

pulsed

pos-

itive,

floodelectrons

are

allowed

through

to

the

phos-

phor

viewing

screen.

Thusa

light

background

glow

is

visible

when

the

CRT

is

used

in

the

variable

persis-

tence

mode.

.

4-19.,

NORMAL.

4-20.

If

the

storage

mesh

potential

is

reduced

to

-25

volts

it

acts

as

a

control

grid

to

flood

gun

electrons

andpreventsthemírom

reaching

the

phosphor.

How-

ever,

it

has

little

affect

on

write

gun

electrons,

allow-

-

ing

many

of

them

to

reach

the

phosphor

viewing

screen.

Some

of

the

write

gun

electrons

strike

the

storage

sur-

face,

charging

it

positive

toward

zero

volts

wherever

they

strike.

Thusthe

CRT

appearstoact

as

a

conven-

tional

CRT

without

variable

persistence

or

storage.

However,

when

the

storage

mesh

is

brought

back

to

-3.3

volts,

those

areas

of

the

storage

surface

which

have

been

struck

by

write

gun

electrons

allow

flood

electrons

to

be

captured

by

the

post

accelerator

field,

and

thus

display

the

pattern

that

was

written

on

the

phosphor

while

the

storage

mesh

was

at

-25

volts.

4-21.

In

order

to

view

a

stored

trace

for

one

minute

or

more,

the

storage

mesh

is

held

at

a

constant

+3.

3

volts.

This

may

be

accomplished

by

reducing

the

width

ofthe

variable

persistence

erase

pulses

to

zero

(corresponding

to

maximum

persistence),

or

by

actu-

ally

disconnecting

the

pulses

from

the

storage

mesh.

The

write

gun

may

be

turned

off

if

desired,

to

prevent

additional

writing

on

the

storage

surface.

4-22.

The

mechanism

which

limits

viewing

time

is

the

"fade

positive"

of

the

storage

surface

(

entire

Screen

illuminated).

This

is

caused

by

positive

ions

reaching

the

storage

surface

and

charging

it

positive.

The

positive

ions

are

generated

by

flood

gun

electrons

striking

residual

gas

molecules

in

the

CRT.

To

ob-

tain

an

extended

storage

time,

the

flood

guns

should

02612-2

Figure

4-4.

Variable

Persistence

Accomplishment

Through

Pulsed

Erasure.

Section

IV

Paragraphs

4-17.to

4-30

STORAGE

MESH

POTENTIAL

|

mp

igla-8-4

|

be

turned

off.

Thisisdone

in

the

STORE

mode;

how-

ever,

thefloodgunsare

turned

on

occasionally

to

per-

mit

viewing

of

the

stored

trace

at

à

reduced

intensity.

4-23.

OVER-ALL

DESCRIPTION.

4-24.

GENERAL.

4-25.

The

Model

181A/AR

Oscilloscope

consists

of

à

low-

voltage

power

supply,

a

calibrator,

four

external

output

isolation

amplifiers,

a

high

voltage

power

sup-

ply,

a

gate

amplifier,

à

horizontal

amplifier,

and

storage

and

variable

persistence

puise

circuitry.

Fig-

ure

4-5

shows

the

functional

relationship

of

these

cir-

cuits.

The

instrument

may

be

operated

as

a

general

purpose,

a

variable

persistence,

or

a

storage

oscil-

loscope.

Circuitoperationin

all

three

modes

is

des-

scribed

in

this

section.

4-26.

Three

input

signals--intensity,

horizontal

de-

flection,

and

vertieal

deflection--are

necessary

to

obtain

a

usable

display

on

the

CRT.

The

circuitry

for

the

intensity.

and

horizontal

deflection

signals

is

ex-

plained

in

the

foliowing

paragraphs

which

are

refer-

enced

to

Figure

4-5,

The

vertical

deflection

signal

is

coupled

to

the

CRT

from

the

Vertical

Plug-In.

4-27.

INTERNAL.

4-28.

Horizontal

deflection

signals

may

be

obtained

from

the

Horizontal

Plug-In

by

positioning

the

HORI-

.

ZONTAL

DISPLAY

switch

to

INT.

Thisapplies

-100

voltstothe

plug-in

which

produces

an

unbianking

gate

and

generates

an

internal

sweep

signal.

4-29.

The

unblanking

gate

is

coupled

from

the

Hori-

zontal

Plug-Into

the

gateamplifier

where

it

is

summed

with

the

Z-Axis

Input,

chopped

blanking

signals,

and

the

unblanking

signal

from

the

storage

pulse

circuit.

The

resulting

signal

is

amplified,

coupled

through

the

high

voltage

power

supply,

and

applied

to

the

CRT

write

gun

grid

to

control

the

display

intensity.

4-30.

Each

unblanking

gate.

signal

developed

by

the

gate

amplifier

also

generates

analternate

trigger

sig-

nai.

This

alternate

trigger

is

directly

coupled

to

the

Vertical

Plug-In.

(The

Operatingand

Service

Manual

for

the

Vertical

Plug-In

unit

employed

should

be

re-

ferred

to

for

the

signal

function.

)

4-3

Section

IV

Model

181A/AR

Figure

4-5

l

HORIZONTAL

PRE-AMP

©

[Position

Q

MAGNIFIER

i

|

t

:

HORIZONTAL

INTERNAL

.

|

AMPLIFIER

DEFLECTION

SWEEP

TT

i

|

5

|

INTERNAL

pe

2

-

-O

[FIND

BEAM

DISPLAY

"NT

t

|

te

KV

HORIZONTAL.

-100V

PLUG—

IN

Ọ

INTENSITY-

VERTICAL

j

DEFLECTION

]

i

|

UNBLANKING

T

HIGH

GATE

vertical

f

<—

ieee

GATE

VOLTAGE

om

my

PLUG-IN

S

e

CHOPPED

AMPLIFIER

POWER

IZ-

AXIS!

BLANKING

SUPPLY

|

INPUT!

+7KV

-=

TO

POST

i

ACCEL

f

O

[Focus}

ERASE

Ọ

UNBLANKING

GATE

!

+156V

—

à

©

PULSER

CIRCUIT

AA

CALIBRATOR

EOSS

i

|

MAX.WRITE

Ò

Ó

423V

UNREG

RON

REAR

LOW

+156V

HORIZONTAL.

PANEL

VOLTAGE

4OOV

PLUG-IN

SIGNALS

-

POWER

f

ay

-26V

-100V

STORE

IBiA-C-i

Figure

4-5.

Overali

Block

Diagram

4-4

02612-2

Model

181A/AR

.

4-31.

The

internal

sweep

from

the

Horizontal

Plug-

In

is

coupled

through

the

HORIZONTAL

DISPLAY

switch

to

the

horizontal

output

amplifier.

Here

it

is

^

converted

to

a

differential

signal,

amplified,

and

ap-

plied

to

the

CRT

horizontal

deflection

plates.

4-32.

EXTERNAL.

4-33.

Positioning

the

HORIZONTAL

DISPLAY

switch

_to

EXT

removes

the

internal

display

voltage

from

the

Horizontal

Plug-In.

The

unblanking

gate

and

the

in-

ternal

sweep

are

therefore

not

generated

by

the

plug-

in.

4-34.

Gate

amplifier

operation

(and

thus

CRT

intens-

ification)

is

determined

by:

an

externally

applied

Z-

'

Axis

Input

signal,

the

chopped

blanking

signal

from

the

Vertical

Plug-In,

and

an

unblanking

signal

from

the

storage

pulsecircuit.

Whenin

EXT,

the

gate

amp-

.

lifier

will

produce

an

alternate

trigger

only

if

the

ex-

-

ternal

input

signal

is

similar

to

the

normal

unblanking

gate.

4-35.

The

externally

applied

horizontal

deflection

sig-

nal

is

preamplified,

coupled

to

the

output

amplifier,

converted

to

a

differential

output,

and

applied

to

the

CRT

horizontal

deflection

plates.

4-36.

CIRCUIT

DESCRIPTION.

4-31.

The

following

paragraphs

area

detailed

descrip-

tion

of

the

circuits

andtheir

functions

in

the

Model

181

A/AR

Oscilloscope.

4-38.

LOW

VOLTAGE

POWER

SUPPLY

(LVPS).

4-39,

The

low

voltage

power

supply

produces

six

dc

voltages

plus

the

CRT

write

and

flood

gun

filament

power.

The

-100,

-12.6,

+15,

+100,

and

+156

volt

supplies

are

regulated

and

used

throughout

the

Model

181A/AR

and

the

plug-in

units.

An

unregulated

423v

is

produced

for

use

by

the

High

Voltage

Power

Supply

(HVPS)

and

the

pilot

lamp.

A

regulated

«105v

is

also

produced

for

use

only

within

the

LVPS.

4-40,

Figure

4-6

illustrates

a

basic

regulated

power

supply.

The

series

regulator

and

the

parallel

combi-

nation

of

the

loadandthe

sensing

device

divide

the

en-

tireapplied

voltage.

Ifthe

loadchanges,

thus

changing

the

voltage

drop

across

the

load,

the

sensing

device

will

detect

it

and

cause

the

resistance

of

the

series

regulator

to

change

in

the

required

manner

to

restore

the

output

to

the

desired

voltage

level.

4-41.

Refer

to

the

schematic

diagram

of

the

LVPS,

`

Figure

8-21.

Theclosing

of

S5

supplies

power

to

the

primary

of

Ti.

The

dual

primary

windings

of

T1

may

be

connected

in

series

for

230v

operation

or

in

para-

llel

for

115v

operation.

$6,

located

on

the

rear

panel

of

the

instrument,

switches

these

windings

for

115v

or

230v

operation.

4-42.

The

ac

voltages

developed

by

the

secondary

wind-

ings

of

T1

are

bridge

rectified,

filtered,

fused

and

applied

to

the

regulatingcircuits.

Decoupling

RC

and

LC

filter

networks

are

employed

for

circuit

isolation

where

required.

02612-2

Section

IV

Paragraphs

4-31

to

4-48

4-43.

The

-100v

output

is

used

as

a

reference

for

the

other

regulating

circuits.

It

must

be

adjusted

first

since

its

output

will

affect

all

other

regulated

LVPS

outputs.

4-44,

-100

VOLT

SUPPLY.

A

portion

of

the

de

volt-

.

age

from

the

-100v

rectifier-filter

circuit

is

dropped

across

ATR5

and

series

regulator

Q4.

The

remainder

is

dropped

across

the

voltage

divider

network

A8R35,

|

A8R36,

and

A8R37.

If

the

-100v

supply

were

to

de-

crease

in

amplitude,

a

small

portion

of

the

positive-

going

change

would

be

felt

on

the

base

of

A8Q12.

This

change

would

be

coupled

through

A8V2

and

A8Q11

to

the

emitter

of

A8Q12.

The

differencebetween

the

in-

puts

to

A8Q12,

a

positive-going

signal,

is

coupled

throughcurrentamplifier,

A8Q10,

tothe

base

of

series

regulator,

Q4.

Less

voltage

is

dropped

by

Q4,

and

the

-100v

supply

increasestonormal.

A8C8

and

A8R29

prevent

high

frequency

oscillation

of

the

series

regu-

lator.

ABCR8

and

A8CRO9

protect

A8Q11

and

A8Q12

respectively

from

reverse

voltage

breakdown

in

case

the

output

voltage

is

shorted.

AS8CRÍiO

acis

to

prevent

.

reverse

charging

of

A8C10

in

the

event

F6

opens.

A8CR12

protects

A8Q10

and

A8Q4

from

reverse

volt-

age

breakdown

during

instrument

turn-

on.

4-48.

+100

VOLT

SUPPLY.

Operation

of

the

«100v

supply

is

similar

to

the

-

100v

supply

except

that

the

base

of

A8Q2

is

held

at

a

constant

voltage

by

A8V1.

'

Any

variations

in

the

output

are

felt

only

on

the

base

of

A8Q3

and

inverted

prior

to

coupling

throteh

A8Q1

to

the

series

regulator

Q1.

4-46.

+105

VOLT

SUPPLY.

Afiltereddc

voltage

from

A'"CRi-4andA7Ciis

applied

across

A7R2,

A8RÍ

and

breakdown

diode

A8VR1.

Zener

action

keeps

the

top

of

A8VR1

five

volts

more

positive

than

the

bottom,

which

is

at

+100v.

The

+105v

from

A8VR1

is

used

to

-

provide

bias

current

for

A8Q1

and

A8Q3.

4-41.

4156

VOLT

SUPPLY.

The

rectifiedandfiltered

voltage

from

A7CRi-4

and

A7C1

is

applied

across

.

ATRiand

breakdown

diode

A7VR1.

Zener

actionkeeps

the

top

of

A7VR156.

2

volts

more

positive

than

the

bot-

tom,

which

is

at

«100v.

The

156

volt

potential

at

ATVRi

is

applied

to

the

CRT

collector

mesh,

and

is

also

used

for

the

ERASE

function.

4-48.

-12.

6

VOLT

SUPPLY.

The

voltage

from

the

-12.6v

rectifier

filter

is

dropped

across

the

series

regulator

Q3,

A8R22,

and

the

load.

Any

variation

in

output

is

coupled

through

voltage

amplifier

A8Q9

and

current

amplifier

A8Q7

to

the

base

of

the

series

regu-

lator

Q3.

|

A8C6

and

A8R20

prevent

high

frequency

oscillation

of

the

regulator.

SERIES

REGULATOR

SENSING

mE

ammo

©

t

o

»

G

DEVICE

m

One

OA/AR-

A-6

Figure

4-6.

Basic

Regulated

Power

Supply.

4-5

Section

IV

.

Paragraphs

4-49

to

4-59

4-49.

The

current

limiter,

A8Q8,

and

A8R22

provide

protection

for the

series

regulator,

Q3.

If

the

output

becomes

shorted,

the

voltage

drop

across

A8R22

turns

on

A8Q8.

The

negative

signal

from

the

collector

of

A8Q8

iscoupledthroughthe

driver

A8Q7

to

the

series

regulator

Q3,

tending

to

turn

it

off.

Output

current

is

thus

limitedto

onlythat

required

to

keep

A8Q8

con-

ducting.

4-50.

+15

VOLT

SUPPLY.

The+15

volt

supply

is

sim-

ilar

to

the

-12.

6v

supply

except

that

changes

in

the

output

are

applied

tothe

base

of

A8Q6

and

inverted

be-

`

fore

being

coupled

through

A8Q4

tothe

series

regula-

tor,

A8Q2.

4-51.

PLUG.IN

POWER.

:

4-52.

Table

4-1

lists

the

current

available

from

each

power

supply

for

use

by

the

vertical

and

horizontal

plug-ins.

Users

desiring

to

design

special

purpose

circuits

should

not

exceed

the

capabilities

shown

in

‘the

table.

Thereisno

minimum

current

requirement

‘for

any

supply.

Table

4-1.

LVPS

Current

Capabilities

Power

Supply

l

Maximum

Safe

-

Current

Available

{

+100

VDC

+15

VDC

-12.6

VDC

-100

VDC

4-53.

CALIBRATOR.

4-54.

The

calibrator

circuit

performs

a

dual

function--

it

provides

a

1kHz

output

signal

of

10v

pk-pk,

+1%

for

calibration

purposes,

and

a

lkHz,

-100v

signal

for

.

the

storage

pulse

circuit

(see

Figure

8-15),

A1Q6

and

A1lQ7

areusedina

free-running

multivibrator

circuit.

Diodes

A1CR12

and

A1CR14

provide

voltage

protection

to

the

transistors.

The

collector

of

A1Q

is

discon-

HV

OSCILLATOR

35KHZ

HV

XFMR

+100V

REGULATOR

l

'

E

HV

ADJUST

Model

181A/AR.

nectedfrom

A1C15

by

AIC

R13

as

A1Q7

turns

off,

pro-

vidinga

faster

pulse

rise-time.

AlL2andA1C

16

isolate

the

multivibrator

from

the

-100v

supply,

while

A1R31

and

A1C17

isolate

it

from

the

«15v

supply.

The

10v

square

wave

output

is

applied

to

a

front-panel

connec-

tor

foruse

inprobe

compensation

and

sensitivity

cali-

‘bration,

and

the

-100v

square

wave

output

from

the

collector

of

A1Q6

is

applied

to

the

pulse

circuit.

4-55.

OUTPUT

ISOLATION

AMPLIFIERS.

4-56.

Signals

derivedfrom

the

Horizontal

Plug-In

are

coupled

to

rear

panel

BNC

connectors

J5-8

(refer

to

Figure

8-7).

Four

emitter

followers,

A2Q1-4,

are

employed

as

isolation

amplifiers.

The

signals

actu-

ally

developedare

determined

by

the

Horizontal

Plug-

Inusedinthe

instrument;

hence,

the

signals

available

can

be

determined

by

referring

to

the

Operating

and

Service

Manual

for

the

applicable

plug-in.

4-57.

HIGH

VOLTAGE

POWER

SUPPLY.

(HVPS).

4-58.

Three

regulated

voltages

are

produced

by

the

HVPS:

-1440v,

+7kv,

and

a

control

grid

voltage

of

-1450v

to-

1500v

(refer

to

Figure

4-

T).

A

regulated

oscillator

isusedto

develop

the

required

high

voltages

in

transformer

A5T1.

The

-1440v

supply

is

sampled

to

provide

control

of

the

osc

illator

output

and

thus

reg-

ulate

all

three

voltages.

4-59.

Unregulated

+23v

from

the

LVPS

aroeiies

pri-

mary

power

to

oscillator

Q5

operating

at

approximately

35kHz

(see

Figure

8-18).

The

outputs

from

the

high

voltage

transformer

A5

T1

are

coupledtotwo-half

wave

rectifier/filter

circuits

and

to

a

voltage

tripler/filter

circuit.

CRT

control

grid

voltage

is

rectified

by

ASCR1

and

filtered..

Thé

write

gun

cathode

voltage

is

rectified

by

ASCR2

while

A5R2

establishes

the

dc

potential

applied

to

its

control

grid.

Voltage

regula-

tors,

A1V1i

and

A1V2,

limit

the

maximum

potential

difference

between

the

control

grid

and

the

cathode

to

140v.

The

CRT

focus

voltage

is

obtained

from

the

-1440

cathode

voltage

by

a

voltage

divider

network

of

'

which

R5,

the

FOCUS

control,

is

a

part.

Resistor,

VOLTAGE

TRIPLER

:

RECTIFIER

&

FILTER

RECTIFIER

M

=~l470V

&

FILTER

RECTIFIER

&

FILTER

BIA

Bi

Figure

4-7.

HVPS

Block

Diagram.

4-6

02612-1

Model

181A/AR

UNBLANKING

GATE

'

CHOPPED

BLANKING

Z-AXIS

INPUT

PULSE

INPUT

-100V

—

x

INT

;

DISPLAY

—

(-100V)

|...

VERT

BEAM

FINDER

FIND

BEAM]

^

-26V

—

/

INTENSITY

9l

Section

IV.

Paragraphs

4-60

to

4-67

“AMPLIFIER

UNBLANKING

SIGNALS

DIFFERENTIATOR

ALTERNATE

TRIGGER

iBIA-

B--3A

Figure

4-8.

Gate

Amplifier

Block

Diagram.

R6,

maintainsthe

write

gun

filamentat

cathode

poten-

tial.

The

voltage

tripler

circuit

of

ASCR1-3and

A9C1-4

is

contained

on

Assembly

A9,

the

output

of

which

(+7

kv)

is

applied

to

the

CRT

post-accelerator

anode.

4-60.

Changes

in

output

of

the

-1440vdc

supply

are

de-

tected

by

the

regulator

A1Q8-A1Q10tochange

the

oper-

ating

voltage

of

oscillator

Q5.

Assume

that

the

-

1440

supply

voltage

decreases

(goes

positive).

Apositive-

-

going

signal

is

applied

through

the

regulator

to

the

base

of

Q5,

causing

it

to

conduct

for

a

greater

portion

oftheinputcycle.

The

oscillation

amplitude

is

there-

fore

varied

so as

to

oppose

the

original

change

in

out-

put

voltage.

This

causes

a

voltage

change

to

appear

on

the

primary

of

A5T1

and

increases

the

voltage

of

the

secondary.

The

steady

state

value

of

the

CRT

cathode

voltage

is

established

by

A1R38,

the

High

Voltage

Adjust,

by

setting

the

normal

dc

value

on

the

base

of

the

A1Q8.

Inductor

A4L1

suppresses

any

pos-

sible

high

frequency

parasitic

oscillation.

4-61.

GATE

AMPLIFIER.

4-62.

The

inputs

to

the

gate

amplifier

(refer

to

Fig-

ure

4-8)

aretheunbianking

gate,

the

chopped

blanking,

the

Z-AXIS

INPUT,

andthe

storage

pulse

circuit

sig-

nals.

These

four

signals

may

be

present

either

singly

or

simultaneously,

depending

upon

control

settings.

They

are

summed

with

a

current

established

by

three

-front

panel

controls--FIND

BEAM,

INTENSITY,

and

HORIZONTAL

DISPLAY.

Depressing

FIND

BEAM

.

shunts

the

normally

adjustable

INTENSITY

control.

and

supplies

maximum

currentfrom

this

source.

Set-

ting

HORIZONTAL

DISPLAY

to

EXT

SENS

or

EXT

CAL

supplies

additional

current

to

brighten

the

beam.

4-63.

The

gate

amplifier,

A1Q1-A1Q4,

senses

the

in-

put

signal

current,

convertsitto

a

voltage,

amplifies

it,

and

couples

itto

the

control

grid

of

the

CRT

write

gun.

And

in

addition,

the

output

signal

is

also

differ-

entiated,

clipped,

and

coupled

to

the

Vertical

Plug-

In

for

use

as

a

trigger

signal

if

desired.

02612-2

4-64.

The

input

currents

to

the

gate

amplifier

(refer

to

Figure

8-7)

are

summed

in

the

low

impedance

emitter

circuit

of

A1lQ1.

The

resulting

current

is.

coupled

to

the

complementary

feedback

amplifier

(a

current

fed

operational

amplifier),

A1Q2-A1Q4,

where

it

is

converted

to

a

voltage

and

coupled

to

the

control

grid

of

the

CRT

write

gun.

The

large

negative

feed-

backfromthe

collectors

of

A1Q3

and

A1Q4

to

the

base

of

A1Q2

provides

the

complementary

feedback

ampli-

fier

with

a

very

stable

gain,

Trimmer

capacitors,

A1C8

and

A1C9,

adjust

the

high

frequency

feedback.

Diode

A1CR6

provides

temperature

compensation

for

A1Q3,

while

AICR7

and

A1CR8

protect

A1Q3

and

A1Q4

from

voltage

breakdown.

Diode,

A1CR10

and

A1R5T,

isolate

A1Q3

and

A1Q4

from

the

high

voltage

inthe

con-

trol

grid

circuit

of

the

CRT

write

gun

in

the

event

of

a

grid

or

cathode

short

to

ground.

The

output

from

A1Q3andA1Q4

is

differentiated

by

A1C13,

A1R22

and

A1R23,

andcoupled

through

A1Q5

andthe

positive

clip-

per,

AÍCRi1i,

to

the

Vertical

Plug-In

for

alternate

triggering

purposes.

4-65.

HORIZONTAL

AMPLIFIER.

4-66.

The

block

diagram,

Figure

4-9,

illustrates

the

majorcircuitfunctions.

The

horizontal

amplifier

can

be

driven

by

either

an

internally

derived

signal

or

by

an

external

signal

applied

to

the

HORIZONTAL

EXT

INPUT

front

panel

BNC

jack.

Positioning

the

HORI-

ZONTAL

DISPLAY

controlto

INT

disconnects

the

ex-

ternal

signal

input

and

grounds

the

horizontal

preamp-

lifier

input.

The

Internal

Sweep

signal

is

connected

through

the

HORIZONTAL

DISPLAY

switch

to

the

hor-

izontal

output

amplifier.

4-67.

The

EXT

INPUT

BNC,

J4,

is

connected

to

the

.

input

of

the

preamplifier

when

either

EXT

SENS

or

EXT

CAL

is

selected;

the

preamplifier,

in

turn,

is

coupledtothe

outputamplifier.

Selections

of

EXT

SENS

permits

varying

theamplitude

of

the

preamplifier

out-

put

by

adjustment

of

the

HORIZONTAL

DISPLAY

con-

4-7

Section

IV

Paragraphs

4-68

to

4-75

DISPLAY

Model

1814/AR

O

|

t

CRT

HORIZONTAL

DEFLECTION

PLATES

R3

o

HORIZONTAL

E

POSITION

I8LA—B—2

Figure

4-9.

Horizontal

Amplifier

Block

Diagram.

trol.

When

EXT

CAL

is

selected,

this

control,

Ri,

is

shorted;

the

output

amplitude,

therefore,

is

deter-

mined

by

the

amplitude

of

the

input

signal.

4-68.

The

signal

selectedis

fed

into

the

output

ampli-

fier

where

it

is

summed

with

a

current

established

by

the

HORIZONTAL

POSITION

controls.

Theresultant

current

is

converted

to

a

differential

signal,

ampli-

fied,

andappliedto

the

C

RT

horizontal

deflection

plates.

4-69,

External

input

signalsare

preamplified

by

A3Q1

.

and

A3Q2

(refer

to

Figure

8-10).

The

high

input

im-

pedance

of

A3Q1

minimizes

loading

of

the

external

in-

put

source.

Diode

A3CR1

protects

A3Q1

from

high

level

inputs.

A3Q2

has

a

low

output

impedance

suit-

able

for

driving

A3Q3.

The

BANDWIDTH/PHASE

Switch,

A3S1,

would

be

positioned

in

PHASE

when

accu-

rate

X-Y

measurement

is

desired.

In

the

PHASE

position,

A3C2and

A3C3

arè

switched

in,

decreasing

the

preamplifier

bandwidth.

'Thetotalhorizontalamp-

lifier

signal

delay

is

therefore

made

equal

to

signal

delay

in

the

Vertical

Plug-In.

The

vernier

balance,

ASR",

is

adjusted

so

that

0

vde

appears

across

the

HORIZONTAL

DISPLAY

control,

thus

eliminating

any

horizontal

dc

shift

as

the

control

is

operated.

4-70.

Input

signals

to

A3Q3

are

summed

in

the

low

im-

pedance

emitter

circuit

with

a

current

established

by

the

setting

of

the

POSITION

controls

A3R2

and

A3R3.

A3Q6

is

driven

by

the

low

impedance

of

emitter

fol-

lower

À3Q4.

The

input

signal

to

A3Q6

is

coupled

through

the

MAGNIFIER

switch,

$4,

tothe

complemen-

`

tary

driver

A3Q7.

S4

provides

for

selection

of

incre-

mental

gain

levels

by

selecting

the

amount

of

emitter

degenerationemployed

with

A3Q6

and

A3Q7.

Increas-

ing

degeneration

decreases

gain.

Adjustment

A3R30

along

with

A3R31

controls

the

gain

when

in

the

X10

position,

A3R32/A3R33

control

the

X5

gain,

and

A3R34/

AS3R35determinethe

X1

horizontal

gain,

The

dc

bal-

ance

of

A3Q6

and

A3Q7

is

adjusted

by

A3R37

which

controls

the

emitter

potentials.

Transistor

A3Q5

pro-

vides

a

low

impedance

voltage

source

for

the

base

of

ASQ.

The

differential

signalat

the

collectors

of

A3Q6

and

A3Q7

is

applied

to

the

complementary

feedback

amplifiers

(current-fed

amplifiers),

A3Q8-Q10

and

A8Q11-Q13,

convertedtoa

voltage,

and

coupled

to

the

horizontal

deflection

plates

of

the

CRT.

A3CR3

pre-

vents

A3Q6

from

saturating,

while

A3CR6

serves

the

same

purpose

for

A8Q7.

Diodes

A3CR2/CR4

and

4-8

.

wave

signal.

A3CR7/CR8

limit

the

amplifier

output

to

the

CRT

de-

.

flection

plates

to

within+6vand

«94v

regardless

of

the

amplitude

of

the

input

signal.

4-11.

Depressing

FIND

BEAM

switch

83

disables

lim-

iter

ASCR7

/CR8

andblocks

the

input

signal

to

A3Q11.

The

differentialgainis

effectively

reduced

by

half

and

the

electron

beam

is

confined

to

the

horizontal

limits

of

the

CRT

screen.

4-12.

The

gain

of

the

complementary

feedback

ampli-

fier

is

made

very

stable

by

coupling

a

generous

amount

of

negative

feedback

from

the

collectors

of

A3Q9/Q10

to

the

base

of

A3Q8,

andfrom

the

collectors

of

A3Q12/

Q13

to

the

base

of

A3Q11.

The

high

frequency

feed-

back

of

each

amplifier

is

adjusted

by

A3C6

or

A3C19

individually,

while

A3C9

adjusts

the

feedback

for

both.

Diodes

A3CR5

and

A3CR9

provide

temperature

compen-

sation

for

A3Q10

and

A3Q13.

4-73.

PULSE

CIRCUIT.

4-14.

Pulses

of

adjustable

level

and

width

are

used

to

controlthe

variable

persistence

and

storage

capability

of

the

Model

181A/AR

Oscilloscope.

They

are

ap-

plied

to

the

CRT

storage

mesh

when

operating

in

the

WRITE

and

MAX

WRITE

modes,

applied

to

the

flood

gun

accelerator

in

the

STORE

mode,

and

used

to

key

the

gate

amplifier

for

CRT

unblanking.

4-75,

VARIABLE

PERSISTENCE,

The

multivibrator

circuit,

(Figure

8-17),

isthe

source

of

a

1

kHz

square

This

signal,

in

turn,

is

applied

to

the

pulse

circuit

which

modifies

the

width

and

level

of

the

pulse.

A

-100v

square

wave

is

obtainedfrom

the

junc-

tion

of

A1C14

and

A1R28

and

fed

to

the

base

of

A6Q3

through

A6R8.

Inverted

and

level-shifted

by

A6Q3,

the

resultant

«15v

square

wave

atthe

collector

of

A6Q3

is

applied

through

A6CR2

and

differentiated

byA6R13/

A6C2.

Applied

to

the

base

of

A6Q4

through

A6CR3,

the

amplitude

of

the

pulse

at

the

anode

of

AGCR3

is

established

by

the

ratio

of

AGR12

andthe

PERSISTENCE

control

setting,

R9.

Asaresult

of

the

charging

time

constant

of

A6C2/A6R13,

the

variable

amplitude

sig-

nalisfeltas

a

variation

in

width

(i.e.

duration)

at

the

base

of

A6Q4.

By

varyingtheconduction

time

of

A6Q4,

thetime

requiredtoeraseatrace

has

been

controlled.

In

other

words,

varying

the

erase

time

is

essentially

the

same

as

varying

the

display

time,

and

this,

in

turn,

is

known

as

variable

persistence.

02612-2

-Model

181A/AR

4-76.

NORMAL.

Selection

of

this

mode

permits

the

Model

181A/AR

tobe

employedas

a

conventional

oscil-

loscope.

With

NORMAL

activated,

the

junction

of

A6R16/A6R19

is

grounded

and

the

storage

mesh

falls

to

-25v.

Because

of

this

negative

potential,

the

vari-

able

persistence

and

storage

capabilities

are

therefore

disabled.

4-77.

WRITE

and

MAX

WRITE.

Operating

in

these

modes

allows

normal

viewing

of

the

display

and

pre-

pares

it

for

storing.

MAX

WRITE

is

used

only

when

necessary,

suchas

in

viewing

fast

single-shot

signals.

'

4-78,

To

obtain

display

uniformity

in

the

MAX

WRITE

mode,

the

CRT

collimator

voltage

should

be

readjusted

in

this

mode.

Todo

so,

a

multivibrator

consisting

of

A6Q16

and

A6Q17

is

used.

4-19.

Whenthe

MAX

W.

pushbutton

is

depressed,

one

side

of

the

multivibrator

conducts.

Current

flow

through

A6R47

and

A6R46

holds

A6Q16

on

and

A6Q17

off.

Thus,

the

MAX

WRITE

ADJ

pot

A6R17

is

para-

lleled

with

WRITE

ADJ.

Atthe

same

time,

A6R9

is

disabledand

MAX

WRITE

COLLIMA

TION

ADJ

(A6R29)

is

enabled.

The

multivibrator

is

necessary

so

that

proper

collimation

voltage

is

retained

when

the

VIEW

or

STORE

mode

is

selected.

4-80.

The

setting

of

the

WRITE

adjust,

A6R18,

adjusts

the

positive

pulse

level

at

the

collector

of

A6Q4

when

operating

in

the

WRITE

mode,

while

A6R18

in

parallel

with

the

MAX

WRITE

adjust,

A6R17,

adjusts

the

level

in

the

MAX

WRITE

mode.

Pulse

level

control

of

the

1

kHz

pulsestothe

storage

mesh

affords

depth

of

eras-

.

ure

control

which

directly

affects

writing

rate.

In

other

words,

the

more

negative

the

storage

surface

becomes,

the

longer

it

will

take

ittobuilduptoa

level

high

enough

to

store

a

trace

(refer

to

Figure

4-4).

4-81.

STORE.

When

the

STORE

function

is

selected,

the

base

of

A6Q1

is

grounded,

turning

it

off.

This

allows

the

current

flow

through

A6R2

and

A6CRI

to

turn

A6Q2

on.

Meanwhile,

the

«15v

square

wave

sig-

nalatthecollector

of

A6Q3

is

differentiated

by

A6C1/

A6R2

and

applied

to

the

base

of

A6Q2

through

A6CR1.

Thus

A6Q2

hasa

negative

voltage

developed

at

its

base

during

the

charging

time

of

A6C1

which

turns

it

off.

The

time

constant

of

AGCI/A6R2

is

such

that

A6Q2

is

off

for

about

50

microseconds

each

millisecond,

and

only

during

this

short

interval

will

a

positive

poten-

tial

be

applied

to

the

flood

gun

accelerator

grid.

4-82.

While

A6Q2

is

on,

the

flood

gun

accelerator

voltage

is

established

by

voltage

divider

network,

A6R5/A6R6,

at

-9v.

With

A6Q2

switched

off

by

the

differentiated

1

kHz

pulse,

the

accelerator

voltage

is

443v

set

by

the

divider

network

A6R4,

and

A6R6.

4-83.

With

the

accelerator

grid

held

at

-9v,

the

flood

gunelectronsarerepelled.

Thus,

when

in

the

STORE

mode,

the

flood

guns

are

always

on,

but

electronsare

attracted

to

the

storage

mesh

only

when

the

acceler-

.

ator

grid

is

at

a

positive

potential,

about

5%

of

the

time.

This

reduces

the

display

brightness

and

pro-

vides

for

greatly

increased

storage

time.

4-84.

VIEW.

Depressing

the

VIEW

push

button

allows

viewing

à

previously

stored

display

at

a

brightness

level

determined

by

the

intensity

and

persistence

set-

|

tings

duringthe

writing

process.

At

least

one

minute

02612-2

Section

IV

Paragraphs

4-76

to

4-89

of

aggregate

viewing

is

available

without

trace

degrad-

ation.

4-85.

When

in

VIEW,

NORMAL,

WRITE

or

MAX

WRITE

mode

of

operation,

A6Q1

is

turned

on

by

the

currentflowthroughA6Rltoitsbase.

This

effectively

grounds

the

base

of

A6Q2,

holding

it

off

and

keeping

the

flood

gun

accelerator

potential

at

43v.

4-86.

The

flood

gun

grid

levelis

setto

provide

an

op-

^

timum

flood

gun

electron

distribution

at.the

storage

mesh.

This

is

adjustable

and

is

determined

by

the

.

setting

of

A6R42,

whichis

in

series

with

ASR?

and

the

-100v

supply.

Stray

ac

signals

on

the

flood

gun

grid

lead

are

decoupled

from

the

flood

gun

by

A6C4.

4-87.

ERASE.

The

push

button

operating

mode

selec-

tor

switch

does

not

permit

energizing

the

erase

cir-

cuitry

unless

the

WRITE

or

MAX

WRITE

mode

of

operating

has

been

selected.

Activationof

the

ERASE

switch

S7

(refer

to

Figure

8-12)

in

either

of

these

modes

`

applies

+156v

tothe

CRT

storage

meshandto

the

junc-

tion

of

A6R36

and

A6CR6.

The

diode

A6CR6

prevents

application

of

this

+156vtothe

collector

of

A6Q4

during

ERASE,

while

A6CR4

prevents

the

collector

from

ris-

ing

above

+15v

because

of

the

+100v

applied

through

‘the

voltage

divider

formed

by

A6R15,

A6CR5,

A6R16

and

A6R19.

Normally

nonc

onducting,

A6Q13

is

turned

on

by

application

of

the

«156v which

in

turn

shuts

off

A6Q12.

Thispermits

A6C6to

charge

positive

through

A6R33

and

A6R37

to

about

44. 7v.

Theresultant

cur-

.rentthrough

A6R37

causes

A6Q14

toconduct

and

A6Q15

to

cease

conduction.

Currentflowingthrough

A6R43,

A1CR15,

AIR10

and

into

the

emitter

of

A1Q1

causes

the

Gate

Amplifier

to

operate

so

as

to

blank

the

CRT

write

gun.

A

clean

erasure

of

the

storage

mesh

is

thereby

assured

since

no

writing

of

an

input

signal

can

take

place

during

erasure.

4-88.

Releasingthe

ERASE

switch

removes

the

«156v

fromthe

CRT

storage

meshand

from

A6R36.

Current

no

longer

flowsthroughthe

base

of

A6Q13

and

conduc-

tionceases.

This

permits

A6Q12to

conduct

due

to

the

current

flow

through

A6R34

into

its

base.

The

result-

ing

4.

7v

negative

step

atthe

collector

of

A6Q12

is

dif-

ferentiated

by

A6C6/A6R32

and

applied

to

the

base

of

A6Q11,

causing

it

to

cease

conduction.

As

a

result

of

the

charging

time

constant

of

A6R32

and

A6C6,

A6Q11

will

remain

ina

nonconducting

state

for

approximately

100

milliseconds.

During

this

time,

A6C5

is

being

charged

to

«4.5

v

through

A6R31,

AO6R38,

and

A6R2T.

Current

flow

through

A6R38

and

A6CRT7

causes

the

Blanking

Control

Amplifier

A6Q14/A6Q15

and

the

Gate

Amplifier

to

operate

and

blank

the

CRT

write

gun.

4-89.

Control

of

the

voltage

applied

to

the

CRT

colii-

mator

is

desired

during

storage

mesh

erasure.

A

por-

tion

of

the

current

through

A6R31

also

flows

through

A6R27,

placing

A6Q8

in

a

conducting

state,

and

caus-

ing

A6Q9

tocease

conduction.

The

voltage

on

the

base

of

A6Q10,

therefore,

rises

to

nearly

«120v,

causing

heavy

conduction

through

A6Q10.

"This

results

in

its

emitter

rising

to

about

«120v

due

to

the

voltage

drop

across

A6R30.

Since

the

collimator

is

connected

to

the

emitter

of

A6Q10,

the

+

120v

developed

across

A6R30

is

appliedto

the

collimator

while

erasing.

This

ensures

a

more

uniform

erasure

of

the

storage

mesh,

particularly

of

the

periphery

of

the

display

area.

4-9

HP 181A Service manual

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