Tektronix 3b3 User manual

INSTRUCTION

MAN

UAL

Serial

Number

BFE3

Tektronix,

Inc.

S.W.

Millikan

Way

@

P.O.

Box

500

@

Beaverton,

Oregon

070-365

Phone

Mi

4-0161

@

Cables:

Tektronix

863

oe

a

Oy

~

a

i

oe

-ee

e

ee

Type

3B3

TYPE

3B3

TIME

BASE

DELAYED

SWEEP

TRIGGERING

SLOPE

COUBLING

SOlgrE

ExT.

¥

“#

TRIG.

™

oc

*)

ext.

|

VARIABLE

TIME/DIV.

ano

DELAY

TIME

RANGE

(PULL

5X

MAG.)

UNCAL.,

vpig7

MODE

—a\'

8

as

INTEND

OL

INTEN,

\

!

\

Fs

SwP.

DELAY

TIME

NORMAL

or

DELAYING

SWEEP

TRIGGERING

SLOPE

COUPLING

SOURCE

ay

AUTO.

g)

INT.

EXT.

Ls

SINGLE

_

aoa

«-@®

TEKTRONIX,

AORTLAND,

OREGON,

U.S.A.

SECTION

I

CHARACTERISTICS

General

The

Type

3B3

Time

Base

Unit

is

a

plug-in

time

base

generator

designed

for

use

with

Tektronix

Types

561A,

RM561A,

564,

567

and

RM567

Oscilloscopes.

The

Type

3B3

provides

normal

or

delayed

sweeps

at

20

calibrated

rates

from

0.5

microseconds

per

division

to

1

second

per

division.

In

delayed

sweep

operation,

the

Type

3B3

gives

continuous

calibrated

sweep

delay

from

0.5

microsecond

to

10

seconds

after

receipt

of

a

triggering

impulse.

Sweep

Rates

Both

normal

and

delayed

sweep

rates

from

0.5

micro-

second

per

division

to

1

second

per

division

in

20

cali-

brated

steps.

A

variable

control

provides

uncalibrated

sweep

rates

between

steps

and

also

extends

the

slower

rate

to

approximately

2.5

seconds

per

division.

Calibrated

sweep

rates

for

both

normal

and

delayed

sweeps

are

typically

within

1%,

and

in

all

cases

within

3%

of

the

TIME/DIV.

and

DELAY

TIME

RANGE

switch

settings.

Sweep

Magnification

The

display

can

be

magnified

5

times,

extending

both

the

normal

and

delayed

sweep

rates

to

0.1

microsecond

per

division.

Sweep

rate

accuracy

with

the

5X

magnification

remains

within

5%

of

the

TIME/DIV.

and

DELAY

TIME

RANGE

switch

settings.

Sweep

Delay

The

calibrated

sweep

delay

is

continuously

variable

from

0.5

microsecond

to

10

seconds.

Delay

accuracy

is

1%

of

full

scale

reading,

and

delay

time

linearity

is

within

0.2%

of

full

scale

from

5

microseconds

to

2

seconds

of

delay.

Time

jitter

is

less

than

1

part

in

20,000

of

the

maximum

available

delay

interval.

Single

Sweep

All

modes

of

operation

can

be

displayed

as

a

single

sweep

for

photographic

recording.

Triggering

Modes,

Normal

Sweep

Automatic

(15

cps

to

10

mcs),

ac-

or

de-coupled,

+

or

—

slope,

internal

or

external

source.

Triggering

Modes,

Delayed

Sweep

Ac-

or

de-coupled,

+

or

—

slope,

internal

or

external

source.

Internal

Triggering

Requirements,

Either

Time

Base

internal

triggering

with

signals

in

the

frequency

range

from

dc

to

5

mc

requires

a

trigger

amplitude

of

0.2

major

divisions

of

vertical

deflection.

Above

5mc,

the

trigger

re-

quirements

increase,

and

at

10

mc,

a

trigger

amplitude

of

0.5

major

division

of

vertical

deflection

is

required.

External

Triggering

Requirements,

Either

Time

Base

External

triggering

with

signals

in

the

frequency

range

from

de

to

5mc

requires

a

trigger

amplitude

of

0.5

volts.

Above

5mc

the

trigger

requirements

increase

and

at

10

mc,

a

trigger

amplitude

of

1.25

volts

is

required.

Maximum

triggering

signal

is

15

volts

direct,

or

150

volts

through

in-

ternal

attenuator

(operated

by

front

panel

switch).

If

ac

coupling

is

used,

up

to

500

volts

total,

de

and

ac

peak

combined,

may

be

applied

so

long

as

the

ac

component

does

not

exceed

150

volts.

Construction

Aluminum-alloy

chassis.

Front

panel

photo-etched

and

anodized.

Weight

5

pounds

4

ounces.

NOTES

SECTION

2

OPERATING

INSTRUCTIONS

TABLE

2-1

(Cont'd)

General

This

section

explains

the

use

of

the

Type

3B3

as

part

of

an

oscilloscope

system,

the

function

of

the

Type

3B3's

front

panel

controls,

operating

procedures

peculiar

to

the

Type

3B3,

and

how

to

display

a

signal.

Use

The

Type

3B3

Plug-In

Time

Base

Generator

is

normally

used

as

part

of

an

oscilloscope

system

composed

of

the

Type

3B3,

one

of

the

Tektronix

oscilloscopes

listed

in

Section

1,

and

an

appropriate

vertical

amplifier

plug-in.

When

properly

operated,

the

system

can

(a)

determine

if

a

certain

event

is

happening,

(b}

make

accurate

measurements

of

the

event,

and

{c}

display

the

representation

of

the

event

in

a

manner

that

permits

photographing.

The

functions

of

the

Type

3B3

in

such

a

system

are

threefold:

it

provides

accurate

time

bases

for

precisely

measuring

the

time

dimensions

of

the

event

being

analyzed;

it

provides

a

versatile

trigger

cir-

cuit

to

assure

positive

synchronization

of

the

time

bases

with

the

event,

and

the

single

sweep

feature

provides

exposure

control

when

the

display

is

to

be

photographed.

In

as-

sembling

an

oscilloscope

system,

the

Type

3B3

is

inserted

in

the

X-axis

(right

hand)

opening

of

the

oscilloscope.

The

vertical

amplifier

plug-in

(a

non-sampling

vertical

amplifier

of

the

‘3’

series

such

as

the

Type

3AT)

is

inserted

in

the

Y-axis

(left-hand}

opening.

Function

of

Front

Panel

Controls

and

Connectors

The

front

panel

controls

and

connectors

on

the

Type

3B3

are

grouped

into

blocks

according

to

the

sweep

circuit

in

which

they

function.

The

blocks

of

controls

are

outlined

by

a

heavy

black

line

printed

on

the

front

panel.

Controls

common

to

both

sweep

circuits

are

placed

between

the

two

blocks

with

the

exception

of

the

screwdriver

adjustable

SWEEP

CAL.

potentiometer

which

is

located

in

the

bottom

right-hand

corner

of

the

front

panel.

Overcrowding

of

the

front

panel

is

avoided

by

giving

some

controls

multiple

functions

and

making

others

concentric.

Table

2-1

lists

the

function

of

the

individual

controls

and

connectors.

Control

Setting

|

Function

SLOPE

+

Sets

the

delayed-sweep

trig-

gering

circuit

to

trigger

on

the

rising

{+)

slope

of

the

trigger-

ing

signal.

Sets

the

delayed-sweep

trig-

gering

circuit

to

trigger

on

the

falling

(—)

slope

of

the

trig-

gering

signal.

COUPLING

AC.

Inserts

blocking

capacitor

in

the

delayed

sweep

trigger

cir-

cuit

to

block

any

de

compon-

ents

of

the

triggering

signal.

DC

Shunts

triggering

signal

around

blocking

capacitor

and

passes

it

directly

to

delayed

sweep

trigger

circuit.

SOURCE

INT.

Switches

input

of

delayed

sweep

trigger

circuit

to

trigger

source

(vertical

plug-in)

within

the

oscilloscope

system.

EXT.

Switches

input

of

delayed

sweep

trigger

circuit

to

EXT.

TRIG.

connector

on

front

panel.

EXT.

TRIG.

(Connector)

Provides

means

of

connecting

external

trigger

signal

to

the

delayed

sweep

trigger

circuit.

Controls

Common

to

Both

Sweeps

MODE

NORM.

Switches

circuits

in

the

Type

3B3

so

that; the

normal

(de-

laying)

sweep

is

displayed

on

the

crt,

the

sweep

rate

is

set

by

the

normal

sweep

_

timing

switch,

and

sweep

triggering

is

selected

by

the

NORMAL

or

DELAYING

SWEEP

TRIGGER-

ING

controls.

TABLE

2-1

Function

of

Front-Panel

Controls

and

Connectors

Control

[|

Setting

|

Function

Delayed

Sweep

Triggering

Block

LEVEL

Pushed

in

|

When

turned,

sets

the

point

on

(PULL

EXT.

the

slope

of

the

input

wave-

TRIG,

ATTEN.)

form

at

which

the

delayed

sweep

is

triggered.

Pulled

out

|

Switches

an

internal

10X

at-

tenuator

into

the

external

trig-

ger

circuit,

permitting

use

of

external

triggering

signals

in

the

15-

to

150-volt

range.

When

turned,

sets

the

point

on

the

slope

of

the

external

trig-

gering

signal

at

which

the

de-

layed

sweep

is

triggered.

INTEN.

Switches

circuits

so

that

the

de-

layed

sweep

intensifies

a

por-

tion

of

the

normal

sweep,

the

intensified

zone

starts

at

a

point

on

the

normal

sweep

de-

termined

by

the

setting

of

the

DELAY

TIME

control,

the

width

of

the

intensified

zone

is

deter-

mined

by

the

setting

of

the

DELAYED

SWEEP

control,

and

the

DELAYED

SWEEP

TRIGGER-

ING

controls

are

disconnected.

TRIG.

INTEN.

Same

as

INTEN.

setting

except

that

DELAYED

SWEEP

TRIG-

GERING

controls

are

now

con-

nected

and

the

start

of

the

in-

tensified

zone

depends

upon

2-1

Operating

Instructions

—

Type

3B3

TABLE

2-1

(Coni'd}

TABLE

2-1

(Cont'd)

Control

Setting

|

Function

Control

|

Setting

|

Function

the

settings

of

the

DELAY

click

in

the

desired

direction,

TIME

and

DELAYED

SWEEP

then

release.

TRIGGERING

controls.

DELAYED

Any

Selects

and

indicates

the

posi-

DLY'D

Switches

the

Type

3B3

circuits

SWEEP

tion

of

the

delayed

sweep

tim-

SWP.

so

that,

the

crt

display

is

the

ing

switch.

The

white

dot

indi-

delayed

sweep

only;

the

de-

cates

sweep

time

duration

layed

sweep

starts

at

a

point

divided

by

10,

or

time

per

divi-

on

the

normal

sweep

deter-

sion.

(See

explanation

of

mined

by

the

setting

of

the

TIME/DIV

AND

DELAY

TIME

DELAY

TIME

control,

and

the

RANGE

SCALE.)

When

the

DELAYED

SWEEP

TRIGGER-

white

dot

is

located

between

ING

Controls

are

disconnected.

the

two

black

lines

on

the

clear

TRIG.

Same

as

DLY'D

SWP.

setting

plastic

ring,

this

control

also

DLY’D

except

that

the

DELAYED

positions

the

normal

sweep

tim-

SWP.

|

SWEEP

TRIGGERING

controls

ing_switch.

are

connected,

and

the

start

of

VARIABLE

UNCAL.

|

Provides variable (uncalibrated)

the

delayed

sweep

is

determin-

sweep

rates

in

between

the

fix-

ed

by

settings

of

the

DELAY

ed

steps

of

the

sweep

timing

TIME

and

the

DELAYED

SWEEP

switches

and

lights

indicator

TRIGGERING

controls.

light

to

warn

that

sweep

is

un-

POSITION

Pushed

in

|

Positions

trace

on

crt

when

calibrated.

When

the

MODE

(PULL

5X

|

Pulled

out

|

turned.

Switches

in

5X

magni-

control

is

in

NORM.

position,

MAG.)

fication

circuit.

Positions

trace

the

VARIABLE

control

varies

on

crt

when

turned.

the

rate

of

the

normal

sweep.

:

a

;

In

all

other

positions

of

the

TIME/DIV

Fixed

This

is

a

scale

printed

on

the

MODE

control,

the

variable

AND

DELAY

front

panel.

The

scale

is

com-

control

is

in

the

delayed

TIME

RANGE

mon

to

both

the

normal

sweep

sweep,

Seatel

aches

owen

“the

MODE

CAL.

Switches

off

the

UNCAL.

light.

control

is

in

TRIG.

INTEN.,

SWEEP

CAL.

variable

|

Provides

a

means

of

compen-

NORM.,

or

INTEN.

positions,

({screw-

|

sating

for

differences

in

hori-

the

scale

indicates

the

time

per

driver

|

zontal

sensitivity

when

chang-

division

of

the

normal sweep.

adjust-

|

ing

the

Type

3B3

from

one

It

also

indicates

1/10th

the

ment)

oscilloscope

system

to

another.

time

duration

of

the

delayed

;

:

;

sweep.

In

both

DLY'D

SWP.

Normal

or

Delaying

Sweep

Triggering

Block

positions

of

the

MODE

control,

DELAY

TIME

|

variable

|

When

the

MODE

control

is

in

the

scale

indicates

time

per

INTEN.

or

DLY’'D

SWP.

posi-

division

of

the

delayed

sweep,

tions

the

DELAY

TIME

control

and

1/10

of

the

normal

sweep

determines

the

point

on

the

delay

time

range.

normal

sweep

at

which

the

de-

TIME/DIV

Any

Selects

and

indicates

the

posi-

layed

sweep

starts.

When

the

AND

DELAY

tion

of

the

normal

sweep

tim-

MODE

control

is

in

either

TRIG.

TIME

RANGE

ing

switch.

This

control

is

the

position,

the

DELAY

TIME

con-

(Control)

clear

plastic

ring

located

be-

trol

determines

the

point

on

tween

the

DELAYED

SWEEP

the

normal

sweep

at

which

control

and

the

TIME/DIV.

the

delayed

sweep

becomes

AND

DELAY

TIME

RANGE

triggerable.

Delay

time

is

scale.

Position

of

the

normal

read

by

multiplying

the

normal

sweep

timing

switch

is

indicat-

sweep

DELAY

TIME

RANGE

ed

by

two

black

lines

on

the

setting

by

the

reading

of

the

control.

When

the

white

dot

DELAY

TIME

dial.

The

ten

on

the

DELAYED

SWEEP

con-

major

divisions

on

the

DELAY

trol

is

positioned

between

the

TIME

dial

are

units,

the

minor

two

black

lines

on

the

clear

divisions

are

decimal.

plastic

ring,

the

two

sweep

Single

Sweep

NORM.

|

Switches

single

sweep

feature

timing

switches

lock

together

off

and

are

both

turned

by

the

:

DELAYED

SWEEP

controls.

To

SINGLE

|

Switches

the

single

sweep

fea-

unlock,

pull

the

DELAYED

SWEEP

|

ture

on.

SWEEP

control

out,

turn

one

RESET

Resets

the

single

sweep

circuit.

2-2

@

TABLE

2-1

(Coni'd)

Control

Setting

Function

For

single

sweep

operation

of

the

Type

3B3,

push

the

single

sweep

switch

down

to

RESET,

then

release.

If

a

trigger

signal

is

present,

a

single

sweep

will

appear

on

the

crt.

If

there

is

no

trigger

signal

present,

the

READY

light

will

turn

on

and

the

single

sweep

will

occur

when

a

trigger

signal

is

appli-

ed.

LEVEL

(PULL

EXT.

TRIG.

ATTEN.)

Pushed

in

When

turned,

sets

the

point

on

the

slope

of

the

input

wave-

form

at

which

the

normal

sweep

is

triggered.

Pulled

out

Switches

an

internal

10X

at-

fenuator

into

the

normal

sweep

external

trigger

circuit,

permit-

ting

use

of

external

triggering

signals

in

the

15-

to

150-volft

range.

When

turned,

sets

the

point

on

the

slope

of

the

ex-

ternal

triggering

signal

at

which

the

normal

sweep

is

trig-

gered.

SLOPE

Sets

the

normal

sweep

trig-

gering

circuit

to

trigger

on

the

rising

(++)

slope

of

the

trigger-

ing

signal.

Sets

the

normal

sweep

trig-

gering

circuit

to

trigger

on

the

falling

(—)

slope

of

the

trigger-

ing

signal.

COUPLING

AUTO.

Switches

the

normal

sweep

to

free-run

operation.

However,

a

suitable

trigger

will

override

the

auto

circuitry

and

trigger

the

sweep.

AC

Inserts

blocking

capacitor

in

the

normal

sweep

trigger

cir-

cuit

to

block

any

de

compon-

ents

of

the

triggering

signal.

DC

Shunts

triggering

signal

around

blocking

capacitor

and

passes

it

directly

to

normal

sweep

trig-

ger

circuit.

SOURCE

INT.

Switches

input

of

normal

sweep

trigger

circuit

to

trigger

source

(vertical

plug-in)

within

the

os-

cilloscope

system.

LINE

Applies

60

cycle

triggering

sig-

nal

to

normal

sweep

circuit.

EXT.

Switches

input

of

normal

sweep

trigger

circuit

to

EXT.

TRIG.

connector

on

front

panel.

EXT.

TRIG.

(Connector)

Provides

means

of

connecting

external

trigger

signal

to

the

normal

sweep

trigger

circuit.

Operating

Instructions

—

Type

3B3

First

Time

Operation

The

steps

that

follow

are

designed

to

instruct

the

opera-

tor

in

the

use

of

the

Type

3B3.

The

steps

cover

the

controls

to

use,

how

and

when

to

use

it,

and

the

expected

results.

Normal

Sweep

Triggering

Controls

1,

Preset

the

Type

3B3

controls

as

follows:

MODE

NORM.

POSITION

Center

of

range

and

pushed

in

DE-

LAYED

SWEEP.

Line

up

the

white

dot

between

the

two

black

lines

on

the

clear

plastic

ring,

then

set

the

two

black

lines

to

straddle

the

5mSEC

position

on

the

TIME/DIV

AND

DELAY

TIME

RANGE

scale.

VARIABLE

CALIB.

NORMAL

OR

DELAYING

SWEEP

TRIGGERING:

LEVEL

Center

of

range

and

pushed

in.

COUPLING

AUTO.

SOURCE

INT,

Single

Sweep

NORM.

2.

Turn

the

instrument

on

and

connect

a

cable

from

the

oscilloscope

calibrator

to

the

input

connector

on

the

vertical

amplifier

plug-in.

3.

Set

the

calibrator

output

for

1

volt

and

adjust

the

VOLTS/DIV.

switch

on

the

vertical

amplifier

plug-in

for

several

divisions

of

vertical

deflection.

There

should

now

be

several

cycles

of

a

steady

(triggered)

calibrator

waveform

on

the

ert.

4.

Turn

the

LEVEL

control

fully

clockwise.

The

display

should

float

(free-run)

across

the

crt.

Now

return

the

control

slowly

toward

the

center

until

the

display

seems

to

lock

into

a

steady

position.

Turn

the

control

fully

counterclockwise;

again

the

display

should

float.

Turn

toward

the

center

until

the

display

locks

into

a

steady

position.

Try

this

several

times

from

both

ex-

tremes

of

the

control.

When

the

display

locks

into

a

steady

position,

the

sweep

is

triggered.

5.

Set

the

COUPLING

switch

to

DC.

Turn

the

LEVEL

control

to

center.

The display

should

be

steady.

Now

turn

the

control

away

from

center;

notice

that

instead

of

free-running,

the

trace

disappears.

6.

Set

the

COUPLING

switch

to

AC;

the

controls

should

have

the

same

effect

as

in

step

5.

7.

Notice

that

the

display

starts

at

either

the

top

or

the

bottom

of

a

pulse.

Set the

SLOPE

switch

to

the

op-

posite

polarity;

the

trace

should

reverse

and

start

opposite

to

its

first

condition.

8.

Connect

a

cable

from

the

calibrator

to

the

NORMAL

or

DELAYING

SWEEP

TRIGGERING,

EXT.

TRIG.

con-

nector.

Set the

SOURCE

switch

to

EXT.

9.

Repeat

steps

4

through

7.

Notice

that

the

trigger

controls

work

the

same

as

for

interna!

trigger

signals

except

that

the

LEVEL

adjustment

may

be

more

critical.

External

trigger signals

should

be

used

in

certain

ap-

plications,

and

these

are

explained

later

in

the

text.

2-3

Operating

Instructions

—

Type

3B3

Delayed

Sweep

Controls

1.

Set the

NORMAL

OR

DELAYING

SWEEP

TRIGGER-

ING-SOURCE

switch

to

INT.,

COUPLING

to

AUTO.,

and

adjust

the

controls

for

a

steady

display.

2.

Set

the

DELAY

TIME

control

to

5.00

and

turn

the

MODE

control

to

INTEN.

(to

the

right

of

NORM.)

3.

Pull

the

DELAYED

SWEEP

control

out

and

turn

it

one

click

to

the

right.

Adjust

the

INTENSITY

control

on

the

oscilloscope

and

notice

that

a

portion

of

the

dis-

play

is

intensified.

Turn

the

DELAY

TIME

control

and

the

intensified

portion

moves

across

the

crt.

4.

Turn

the

DELAYED SWEEP

control

further

to

the

right.

Each

click

makes

the

intensified

display smailer

al-

though

it

can

still

be

moved

by

the

DELAY

TIME

con-

trol.

5.

Turn

the

MODE

control

to

DLY’D

SWP

(on

the

right).

The

intensified

zone

seen

in

the

should

expand

and

cover

the

full

width

of

the

crt.

The

width

of

the

intensified

zone

set

in

step

4

is

always

ex-

panded

to

the

full

width

of

the

ert

when

the

MODE

control

is

turned

to

DLY'D

SWP.

The

following

steps

cover

the

DELAYED

SWEEP

TRIGGER-

ING

controls

at

the

top

of

the

Type

3B3.

1.

Return

the

MODE

control

to

NORM.

and

the

TIME/-

DIV

and

DELAY

TIME

RANGE

controls

to

5

mSEC.

2.

Set

the

DELAYED SWEEP

TRIGGERING

controls

as

follows:

LEVEL

fully

counterclockwise

SLOPE

+

COUPLING

AC

SOURCE

INT.

3.

Turn

the

MODE

control

to

TRIG.

INTEN.

and

adjust

the

INTENSITY

control

so

that

the

display

is

barely

visible.

Turn

the

Delayed

Sweep

LEVEL

control

through

its

range;

notice

a

portion

of

the

trace

intensifies

as

the

control

passes

midrange.

Leave

the

contro!

at

mid-

range.

4.

Pull

out

the

DELAYED SWEEP

control

and

turn

it

sev-

eral

clicks

to

the

right.

The

intensified

portion

of

the

display

will

get

smaller.

5.

Turn

the

MODE

control

to

TRIG.

DLY'D

SWP;

the

in-

tensified

portion

of

the

display

expands

across

the

full

width

of

the

crt.

6.

Set

the

delayed

sweep

SLOPE

control

to

the

opposite

polarity;

the

display

should

invert

and

remain

stable.

7.

Set

the

delayed

sweep

COUPLING

switch

to

DC;

the

display

may

disappear.

Readjust

the

delayed

sweep

LEVEL

control

and

the

display

should

return.

8.

Connect

a

cable from

the

calibrator

to

the

Delayed

sweep

EXT.

TRIG.

jack.

Set the

SOURCE

control

to

EXT.

Adjust

the

delayed

sweep

LEVEL

control,

if

necessary,

until

the

trace

appears.

The

following

description

covers

single

sweep

operation.

Single

sweep

can

be

used

with

either

normal

or

delayed

sweep.

2-4

First

set

the

controls

for

a

normal

triggered

display

(use

INT.

coupling).

Then

push

the

single

sweep

control

to

RE-

SET

and

a

single

sweep

will

occur.

To

trigger

a

single

sweep

proceed

as

follows:

1.

Set

the

single

sweep

control

to

SINGLE

SWEEP.

2.

Remove

the

trigger

signal.

This

can

be

done

in

several

ways,

such

as:

a.

Turn

the

Normal

Sweep

LEVEL

control

either

clock-

wise

or

counterclockwise.

b.

Set

the

normal

trigger

SOURCE

control

to

EXT.

c.

Remove

the

input

signal.

3.

Push

the

single

sweep

control

to

RESET

and

release.

The

READY

light

should

turn

on.

4.

Apply

a

trigger

signal

and

the

crt

will

show

a

single

sweep.

Trigger

Selection

The

choice

of

triggering

to

use

depends

on

the

type

and

portion

of

the

signal

to

be

displayed.

For

example,

if

the

display

starts

on

the

leading

edge

of

the

signal

and

it

is

desired

to

start

on

the

trailing

edge,

set

the

SLOPE

control

to

the

other

position.

The

AUTO

position

of

the

COUPLING

is

useful

from

ap-

proximately

15

cps

to

10

mc.

It

has

the

advantage

of

show-

ing

a

trace

when

the

signal

is

removed,

or

when

the

ampli-

fier

input

is

grounded.

This

makes

it

easy

to

check

a

refer-

ence

graticule

line,

since

the

trigger

controls

need

not

be

touched.

The

AC

position

of

the

COUPLING

control

is

the

same

as

for

AUTO

except

for

the

free-run

of

the

display.

Both

the

AUTO

and

AC

positions

reject

any

de

component

in

trigger-

ing

the

signal.

Adjusting

the

POSITION

control

on

the

verti-

cal

amplifier

plug-in

does

not

affect

triggering

in

the

AUTO

or

AC

coupling

positions.

In

the

DC

position

of

the

COUPLING

control,

the

sweep

will

trigger

in

the

range

from

dc

to

10

me.

This

position

should

be

used

with

signals

that

change

slowly,

such

as

a

slow-rising

sawtooth.

The

normal

sweep

LEVEL

control

is

used

to

trigger

the

sweep

at

any

voltage

point

on

these

slow-rising

signals.

With

the

LEVEL

control

centered

the

sweep

will

start

as

the

signal

voltage

crosses

the

zero

volt-

age

point.

For

most

applications

the

trigger

SOURCE

control

should

be

used

in

the

INT.

position.

However,

if

the

frequency

of

the

signal

is

the

line

frequency

(60

cps},

use

the

LINE

position

of

this

control.

External

triggering

should

be

used

when

signals

are

to

be

sampled

from

several

points

within

a

device,

such

as

in

point

to

point

troubleshooting.

With

external

triggering,

the

trigger

controls

do

not

have

to

be

adjusted

for

each

point

check.

Delayed

Triggering

This

type

of

triggering

has

the

advantage

of

practically

eliminating

jitter

in

the

display

during

delayed-sweep

opera-

tion.

Each

sweep

is

triggered

by

the

expanded

portion

of

the

waveform

and

not

by

the

waveform

at

the

beginning

of

the

normal

sweep.

For

example,

assume

a

pulse

train

®

output

from

a

computer

circuit.

You

want

to

examine

a

small

pulse

5

microseconds

from

the

start

of

the

pulse

train.

Use

the

TIME/DIV.

and

the

DELAYED

SWEEP

controls

and

the

TRIG.

DLY’D

SWP

position

of

the

MODE

control

to

expand

the

display

to

show

only

the

small

pulse.

Then

adjust

the

Delayed

Sweep

LEVEL

contro!

for

a

stable

dis-

play.

The

sweep

will

then

be

triggered

by

the

expanded

portion

and

not

by

the

start

of

the

pulse

train.

The

SLOPE,

COUPLING,

and

SOURCE

controls

work

the

same

as

their

counterparts

in

normal-sweep

operation.

The

choice

of

position

for

these

controls

depends

on

the

type

of

waveform

being

examined.

Sweep

Magnification

The

display

can

be

expanded

to

5

times

its

normal

width

by

pulling

out

the

5X

MAG.

control

(POSITION

control).

Each

part

of

the

expanded

display

can

be

examin-

ed

by

turning

the

POSITION

control

through

its

range.

The

sweep

magnifier

extends

the

range

of

the

TIME/DIV.

switch

5

times.

For

example,

with

the

TIME/DIV.

switch

set

at

.5

»SEC

and

the

5X

MAG.

switch

pulled

out,

the

actual

time

per

division

is

0.1

microsecond

(VARIABLE

control

in

Operating

Instructions

—

Type

3B3

the

CALIB.

position).

The

magnifier

works

the

same

for

either

normal

or

delayed

sweep.

Sweep

Cal.

Check

This

check

should

be

made

whenever

the

Type

3B3

is

used

with

a

different

oscilloscope

since

the

deflection

plate

sen-

sitivity

may

not

be the

same.

The

accuracy

of

this

check

de-

pends

on

the

frequency

of

the

power

line

supplying

the

instrument

being

exactly

60

cps,

since

this

frequency

is

used

to

synchronize

the

calibrator.

Make

the

check

as

follows:

1.

Set

the

MODE

control

to

NORM.

2.

Set

the

TIME/DIV.

switch

to

5mSEC

{be

sure

the

5X

MAG.

switch

is

pushed

in}.

3.

Connect

a

cable

from

the

oscilloscope

calibrator

to

the

vertical

amplifier

plug-in

and

adjust

the

normal

sweep

triggering

controls

for

a

stable

display.

4.

There

should

be

exactly

3

cycles

of

the

calibrator

signal

across

the

10

divisions

of

the

graticule.

If

there

is

not,

adjust

the

SWEEP

CAL.

control

until

there

is.

2-5

NOTES

SECTION

3

APPLICATIONS

tt

PULSE

TO

BE

MEASURED

MODE

NORM.

INTEN.

DLY’D

SWP.

{

PULSE

DURATION

{

MODE

NORM.

INTEN.

DLY'D

SWP.

Fig.

3-1.

Pulse

Duration

Measurement

General

This

section

describes

typical

applications

for

the

Type

3B3

Time

Base

unit.

Since

the

number

of

applications

for

the

Type

3B3

is

large,

this

section

covers

only

a

few.

In-

cluded

are

measurements

of

time,

frequency,

phase-shift,

and

waveform

jitter.

Time

Measurements

The

calibrated

sweeps

of

the

Type

3B3

cause

any

hori-

zontal

distance

on

the

crt

to

represent

a

definite

time

inter-

val.

Thus,

the

time

interval

between

points

on

a

display

can

be

accurately

measured

(within

3%).

For

example,

assume

you

have

a

normal-sweep

crt

dis-

play

similar

to

Fig.

3-1

and

you

wish

to

measure

the

dura-

tion

of

one

pulse.

1.

Make

sure

the

VARIABLE

control

is

set

to

CALIB.,

then

pull

out

the

DELAYED

SWEEP

control

and

turn

it

two

clicks

to

the

right.

2.

Turn

the

MODE

control

to

INTEN.

(clockwise},

and

adjust

the

oscilloscope

INTENSITY

control

to

show

an

intensified

zone

on

the

display.

3.

Turn

the

DELAY

TIME

control

until

the

intensified

zone

begins

at

the

start

of

the

desired

circle.

4.

Turn

the

MODE

control

to

DLY'D

SWP.

{clockwise}

and

measure

the

horizontal

distance

from

the

50%

point

on

the

rise of

the

pulse

to

the

50%

point

on

the

fall

of

the

pulse.

Multiply

this

distance

by

the

setting

of

the

DELAYED

SWEEP

control

(setting

of

white

dot

on

large

black

knob).

Measurements

with

DELAY

TIME

Control

The

following

technique

minimizes

human

errors

(paral-

lax,

interpolation

of

graticule

lines)

that

occur

with

graticule

measurements

and

should

be

used

when

more

than

routine

accuracy

is

needed.

(See

Fig.

3-2.)

1.

Set the

MODE

control

to

INTEN.

(clockwise)

and

adjust

the

controls

to

display one

cycle

of

the

signal.

2.

Adjust

the

oscilloscope

intensity

to

make

the

intensi-

fied

part

of

the

trace

stand

out.

Pull

out

the

DELAYED

SWEEP

control

and

turn

it

to

the

right

until

the

intensi-

fied

area

is

a

small bright

dot.

3.

To

measure

pulse

duration,

turn

the

DELAY

TIME

con-

trol

until

the

bright

dot

is

at

the

50%

point

on

the

leading

edge

of

the

pulse.

Record

the

reading

of

the

dial.

For

best

accuracy,

this

reading

should

be

greater

than

1.00.

4.

Turn

the

DELAY

TIME

control

to

move

the

bright

dot

to

the

50%

point

on

the

trailing

edge

of

the

same

pulse

as

step

3.

Record

the

reading

of

the

dial.

5.

Subtract

the

reading

of

step

3

from

that

of

step

4,

then

multiply

the

remainder

by the

setting

of

the

TIME/DIV.

switch.

The

product

is

the

pulse

width.

3-1

Applications

—

Type

3B3

Bright

Dot

Try

RUE?

5

mSEC/DIV

my)

First

Reading

—

3.15

6.48

—

3.15

—

3.33

Bright

Dot

5

mSEC

/DIV

Second

Reading

=

6.48

Time

for

one

cycle

=

3.33

x

5

mSEC

—

16.666

mSEC.

Fig.

3-2.

Time

measurements

with

DELAY

TIME

control

Frequency

Measurements

Time

measurements

may

also

be

used

for

frequency

measurements.

Since

frequency

and

time

are

reciprocal

functions,

the

frequency

of

any

signal

is

the

reciprocal

of

the

period

(time)

for

one

cycle.

For

example,

if

the

time

for

one

cycle

ts

0.2

microsecond,

the

frequency

is

5

megacycles.

TIME/DIV

1

mSEC

eo

2

CYCLES

>

10

mSEC———-->

NUMBER

OF

CYCLES

IN

10

DIVISIONS

10

X

TIME/DIV

SWITCH

SETTING

—

FREQUENCY

(EXPRESSED

IN

SECONDS)

2

10

X

1

mSEC

2

=

"01

See

2

CYCLES

PER

SECOND

Fig.

3-3.

Frequency

Measurement

3-2

With

any

sweep

rate,

the

number

of

cycles

displayed

across

10

divisions

of

the

graticule

depends

on

the

fre-

quency

of

the

waveform

(see

Fig.

3-3).

To

determine

the

frequency,

proceed

as

follows:

1.

Set

the

TIME/DIV.

switch

to

display

several

cycles

of

the

waveform

(be

sure

the

VARIABLE

TIME/DIV.

con-

trol

is

in

the

CALIB.

position).

2.

Count

the

number

of

cycles

across

the

10

divisions

of

the

graticule.

3.

Divide

this

number

by

10

times

the

TIME/DIV.

switch

setting.

This

is

the

frequency

of

the

waveform.

For

example,

assume

that

you

are

using

a

sweep

rate

of

5

mSEC/DIV.

and

you

count

3

cycles

across

the

10

divisions.

Multiply

5

milliseconds

by

10

(number

of

divisions);

this

equals

50

milliseconds

or

0.05

second.

Dividing

3

cycles

by

0.05

second,

the

frequency

is

60

cycles

per

second.

Phase-Shift

Measurement

To

measure

the

phase

difference

between

two

sine

waves,

proceed

as

follows:

1.

Set

up

the

Type

3B3

for

normal-sweep

operation

and

connect

a

triggering

signal

(related

to

the

two

to

be

measured)

to

the

NORMAL

SWEEP

TRIGGERING

EXT.

TRIG.

jack.

Then

connect

one

of

the

signals

to

be

measured

to

the

input

connector

of

the

vertical

ampli-

fier

unit.

2.

Set

the

TIME/DIV.

switch

so

that

at

least

one

cycle

of

the

sine

wave

is

displayed

on

the

crt.

3.

Vertically

center

the

display

and

horizontally

position

it

so

that

one

of

the

positive

slopes

crosses

the

centerline

at

the

left

side

of

the

graticule

(see

Fig.

3-4).

4.

Measure

the

time

duration

of

one

cycle

of

the

wave-

form.

5.

Without

making

any

adjustments,

disconnect

the

first

sine

wave

from

the

vertical

amplifier

and

substitute

the

second.

(Normally

this

can

be

done

simply

by

moving

the

probe

from

one

signal

source

to

the

other.)

Verti-

cally

center

the

display.

If

there

is

a

phase

difference

between

the

two

sine

waves,

you

will

find

that

the

dis-

play

has

shifted

horizontally.

6.

Measure

the

amount

of

horizontal

shift

in

the

display.

{You

may

increase

or

decrease

the

deflection

sensitivity

of

the

vertical

amplifier

to

make

the

measurement

easier,

but

be

sure

the

display

remains

centered.)

7.

Divide

the

distance

measured

in

step

6

by

the

distance

measured

in

step

4

and

multiply

the

result

by

360°.

This

is

the

phase

difference

(within

3%)

between

the

two

sine

waves.

LENGTH

OF

ONE

CYCLE——>

SHIFT

(FROM

STEP

6)

IENGTH

OF

ONE

CYCLE

(step

4)

360°==PHASE

DIFFERENCE

2.5

(div.)

10

div)

X

360

=

90

Fig.

3-4.

Phase

Measurement

Pulse

Jitter

Measurements

Pulse

jitter

is

defined

as

relatively

small

variations

in

pulse

spacing

in

a

pulse

train.

For

example,

assume

a

normal

sweep

pulse

train

is

displayed

on

the

crt,

and

you

wish

to

check

a

small

pulse

in

the

train

for

jitter.

The

following

steps

may

be

used.

1.

Turn

the

MODE

control

to

INTEN.

(clockwise).

Pull

out

the

DELAYED

SWEEP

control

and

turn

it

to

the

right

until

the

intensified

zone

of

the

display

is

about

the

same

width

as

the

pulse

fo

be

checked.

Applications

—

Type

3B3

2.

Turn

the

DELAY

TIME

control

to

move

the

intensified

zone

over

the

pulse.

3.

Turn

the

MODE

control

to

DLY'D

SWP

(clockwise}

and

adjust

the

DELAY

TIME

control

to

place

the

in-

tensified

pulse

at

the

center

of

the

crt.

4.

The

intensified

pulse

will

then

show

jitter

if

present.

The

amount

of

jitter

can

be

measured

(in

time)

by

multiplying

the

horizontal

distance

in

divisions

(of

the

jitter

area;

see

Fig.

3-5)

by

the

setting

of

the

DELAYED

SWEEP

knob

(setting

of

white

dot

on

large

black

knob).

PULSE

JITTER

MODE

JITTER

TO

BE

MEASURED

DLY'D

SWP

Fig.

3-5.

Measurement

of

Pulse

Jitter

Non-repetitive

Pulse

Displays

in

a

device

where

a

trigger

pulse

initiates

a

second

pulse

which

occurs

at

a

later

time,

delayed

sweep

should

be

used.

For

example,

assume

a

trigger

pulse

occurs

in

a

system,

and

five

seconds

later

a

second

pulse

occurs.

Also

assume

that

the

duration

of

the

second

pulse

is

5

milliseconds.

With

a

sweep

of

10

seconds,

the

second

pulse

would

probably

just

be

invisible.

With

delayed

sweep

the

pulse

can

be

examined

in

detail.

The

technique

is

as

follows.

1.

Set

the

TIME/DIV.

switch

of

the

normal

sweep

to

1

SEC.

2.

Set

the

DELAYED

SWEEP

control

to

10

mSEC.

3.

Set

the

DELAY

TIME

control

to

5.00.

4.

Turn

the

MODE

control

to

NORM.

and

adjust

the

con-

trols

for

a

triggered

sweep.

5.

Turn

the

MODE

control

to

DLY'D

SWP

(clockwise).

The

second

pulse

will

be

displayed

5

seconds

after

the

initial

trigger

pulse.

The

pulse

can then

be

photo-

graphed.

NOTES

SECTION

4

CIRCUIT

DESCRIPTION

General

The

Type

3B3

is

a

conventional

time-base

unit

with

de-

layed

sweep.

The

simplified

block

diagram

of

Fig.

4-1

shows

the

relationship

of

the

major

circuits.

The

schematic

dia-

grams

at

the

rear

of

the

manual

should

be

referred

to

when

studying

this

circuit

description.

The

Normal

Sweep

Trigger

circuit

receives

a

signal

from

either

the

Vertical

Amplifier

plug-in

or

from

an

external

source.

The

circuit

converts

the

signal

to

a

trigger

pulse

for

the

Normal

Sweep

Generator.

This

trigger

pulse

switches

a

tunnel

diode

in

the

Normal

Sweep

Generator

and

starts

the

sweep

ramp.

When

the

ramp

voltage

reaches

a

preset

point

(normal

sweep

length},

the

ramp

ends

and

the

crt

beam

{now

blanked)

returns

to

its

starting

point.

A

holdoff

period

delays

the

start

of

the

When

_

this

period

ends,

the

pulse

starts

another

sweep.

The

start

of

the

delayed

sweep

is

controlled

by

the

normal

sweep

rate

and

the

setting

of

the

DELAY

TIME

control.

The

delayed

sweep

rate

is

set

by

the

DELAYED

SWEEP

control.

The

sweep

ramp

from

both

sweep

generators

passes

to

the

MODE

switch.

If

this

switch

is

set

to

NORM.,

INTEN.,

or

TRIG.

INTEN.,

the

normal

sweep

passes

to

the

Horizontal

SOURCE

SWITCH

Amplifier.

In

the

DLY'D

SWP

or

TRIG.

DLY’'D

SWP

positions

of

the

MODE

switch,

the

delayed

sweep

passes

to

the

Horizontal

Amplifier.

The

Horizontal

Amplifier

converts

the

sweep

ramp

to

a

push-pull

output

and

applies

it

to

the

horizontal

deflection

plates

of

the

crt.

The

Delayed

Sweep

Trigger

circuit

operates

only

when

the

MODE

switch

is

in

the

TRIG.

INTEN.

or

TRIG.

DLY'D

SWP

position.

This

circuit

is

identical

to

the

Normal

Sweep

Trigger

circuit

and

uses

a

signal

from

either

the

Vertical

Amplifier

or

an

external

source.

The

trigger

pulse

formed

by

the

Delayed

Sweep

Trigger

circuit

passes

to

the

Delayed

Sweep

Generator

and

starts

the

delayed

sweep

ramp.

The

ramp

ends

when

it

reaches

a

preset

point

(delayed

sweep

length).

During

the

ramp

run-

up

a

positive

pulse

is

coupled

to

the

crt

grid

to

intensify

the

display.

The

two

INTEN.

positions

of

the

MODE

switch

show

an

intensified

area

of

the

display

that

represents

both

the

de-

layed

sweep

duration

and

its

position

with

respect

to

the

start

of

the

normal sweep.

———}>

Intensifying

Signal

To

Crt

EXT.

TRIG.

MODE

SWITCH

|

Oo

O«i—O

DELAYED

SWEEP

>

DELAYED

SWEEP

TRIGGER

GENERATOR

Interconnecting

plug

ad

DELAY

¢—_odto

HORIZONTAL

To

PICKOFF

AMPLIFIER

Crt

>

[

EXT.

TRIG.

O

O———_O—t—_O—

NORMAL

SWEEP

>

NORMAL

SWEEP

TRIGGER

GENERATOR

~

SOURCE

SWITCH

Fig.

4-1.

Simplified

Block

Diagram

of

Type

3B3.

®

4-1

Circuit

Description

—

Type

3B3

Normal

Sweep

Trigger

The

trigger

signal

{internal

or

external)

enters

the

circuit

through

the

SOURCE

switch

and

passes

to

the

COUPLING

switch.

The

COUPLING

switch

passes

the

signal

through

a

capacitor

in

the

AUTO

or

AC

positions;

in

the

DC

position

the

capacitors

are

bypassed.

R9

and

R10

attenuate

the

signal

about

25%

and present

a

high

impedance

load

to

the

signal

source.

When

the

SOURCE

switch

is

in

the

EXT.

position

and

the

PULL

EXT.

TRIG.

ATTEN.

switch

is

pulled

out,

R7

is

paralleled

across

R10

and

the

network

becomes

an

approximate

10

to

1

attenuator.

C7

and

C9

are

frequency

compensating

capaci-

tors.

Neon

bulb

B10

provides

overload

protection

against

high

signal

voltages.

V13

is

a

long-tailed

cathode

follower

that

couples

the

signal

through

diode

D15

to

the

SLOPE

switch.

Diodes

D1I5

and

D16

protect

transistors

Q24

and

Q34

from

excessive

positive

voltages.

The

SLOPE

switch

directs

the

signal

to

either

Q24

or

Q34

depending

on

its

setting.

Q24

and

Q34

are

a

comparator

with

the

signal

applied

to

one

base

and

a

dc

voltage

(set

by

the

LEVEL

control}

on

the

other

base.

Diodes

D24

and

D34

prevent

emitter

to

base

breakdown

of

Q24

and

Q34.

When

the

signal

equals

the

level

voltage,

tunnel

diode

D35

switches.

The

pulse

from

D35

is

amplified

by

Q44

and

applied

to

T101.

This

transformer

couples

the

pulse

to

the

Normal

sweep

generator.

Normal

Sweep

Generator

With

the

COUPLING

switch

in

AC

or

DC

position,

sweep

ramp

generation

starts

when

a

trigger

pulse

coupled

through

Base

rises

to

+2

volts

T101

causes

tunnel

diode

D105

to

switch

to

its

high

state.

This

puts

a

positive

pulse

on

the

base

of

Q114.

Q114

turns

on

hard

and

its

collector

voltage

goes

negative.

This

nega-

tive

change

drops

the

voltage

on

the

plates

of

V152

and

the

tube

cuts

off.

When

V152

cuts

off,

the

timing

capacitor

C160

starts

to

change

toward

—100

volts

through

the

timing

resistor

R160.

As

the

grid

of

VI6TA

starts

to

drop,

its

plate

voltage

starts

to rise.

The

resulting

positive

swing

is

coupled

through

D162

and

V161B

to

the

top

of

C160.

This

in-

creases

the

potential

to

which

C160

is

trying

to

charge.

The

effect

is

to

straighten

out

the

charging

curve

by

in-

creasing

the

charging

voltage

with

each

increment

of

charge

on

the

capacitor.

The

positive

swing

at

the

top

of

the

tim-

ing

capacitor

also

tends

to

keep

the

lower

side

from

drop-

ping.

This

keeps

the

voltage

across

R160

essentially

con-

stant,

providing

a

constant-current

charging

source

for

the

timing

capacitor.

The

result

is

an

extremely

linear

sawtooth

ramp

at

the

cathode

of

V161B,

which

is

then

applied

to

the

horizontal

amplifier.

The

sweep

ramp

ends

when

the

voltage

applied

to

the

base

of

Q145

reaches

approximately

+4

volts.

Fig.

4-2

shows

the

waveform

on

the

base

of

Q145

with

the

condi-

tion

of

associated

diodes.

Fig.

4-3

shows

the

condition

of

D105

{tunnel

diode)

during

a

sweep

cycle.

The

sweep

ramp

voltage

at

the

arm

of

the

NORMAL

SWEEP

LENGTH

control

(R168)

starts

at

about

—38

volts.

D171

is

back-biased

and

the

ramp

voltage

cannot

reach

the

base

of

Q145.

As

the

voltage reaches

+2

volts,

D171

is

forward-biased

and

the

ramp

voltage

is

applied

to

the

base

of

Q145.

Q135

turns

on.

Q145

turns

off.

Sweep

ends.

D172

forward-biased.

Base

drops

to—3

volts.

a

+4—

set

by

R140

and

R141.

+-2—-

v

L

T

0

Ss

D171

forward-biased.

Ramp

voltage

applied

to

base

of

Q145.

3

Sweep

starts,

D172

back-biased

by

ramp

voltage

through

D170.

Sweep

holdoff

Fig.

4-2.

Waveform

at

base

of

Q145

with

condition

of

associated

diodes.

4-2

Quiescent

state.

Current

through

Q145

and

D105

is

about

3.8

ma.

Base

of

Q145

at

—3

volts.

Circuit

Description

—

Type

3B3

Sweep

starts.

When

D171

turns

on, the

base

of

Q145

goes

positive

and

current

is

reduced.

D105

drops

to

point

C.

/

MV

The

base

of

Q145

holds

at

+2

volts

until

D172

(holdoff

period)

turns

on,

then

it

drops

to

—3

volts.

Current

through

Q145

increases

and

D105

moves

to

point

A.

1

500

MV

When

the

emitter

of

Q145

reaches

+5

volts,

Q135

turns on

and

Q145

turns

off.

The

sweep

ends

and

D105

moves

to

point

D.

Fig.

4-3.

Condition

of

Tunnel

Diode

D105

during

sweep

and

holdoff

periods

The

voltage

at

the

emitter

of

Q145

follows

the

base

vol-

tage

in

a

positive

direction.

When

the

emitter

rises

to

+5

volts,

Q135

turns

on.

This

quickly

drops

the

emitter

of

Q145

to

—0.5

volt

and

it

turns

off.

When

Q145

turns

off,

the

current

source

for

D105

is

removed

and

the

tunnel

diode

switches

to

its

low

state.

This

negative

change

turns

Q114

off

and

allows

the

plates

of

V152

to

go

positive.

V152B

conducts

and

timing

capacitor

C160

discharges through

V152B

and

the

cathode

resistors

of

V161B,

ending

the

sweep

ramp.

Sweep

Holdoff

Period

A

holdoff

period

is

necessary

between

each

sweep

to

pre-

vent

display

jitter.

This

is

done

by

preventing

the

sweep

from

being

retriggered

until

the

whole

system

is

again

stable

and

the

electron

beam

is

at

the

left

side

of

the

crt.

The

holdoff

period

is

developed

by

the

charge

and

discharge

of

holdoff

capacitor

C170.

The

circuit

works

as

follows:

During

sweep

run-up,

the

sweep

voltage

charges

C170

through

D170.

When

the

sweep

ends,

C170

discharges

exponentially.

When

the

capacitor

charge

drops

to

about

—3

volts,

D172

becomes

forward

biased

and

this

voltage

is

applied

to

the

base

of

Q145.

Current

through

Q145

in-

creases,

which

causes

tunnel

diode

D105

to

move

to

its

ready

state

(point

A

on

Fig.

4-3).

A

trigger

can

now

start

another

sweep.

Automatic

Sweep

If

the

COUPLING

switch

is

set

to

AUTO.,

transistor

Q124

provides

an

additional

source

of

current

for

Q145.

This

®

added

current

switches

D105

(at

the

end

of

the

holdoff

period)

and

the

sweep

free-runs.

(See

Fig.

4-4).

To

trigger

in

the

AUTO.

position,

a

positive

trigger

pulse

from

T101

is

applied

through

D119

to

a

monostable

multi-

vibrator

consisting

of

transistors

QII5

and

Q125.

The

trigger

pulse

(applied

to

the

base

of

Q125}

turns

on

Q125

and

the

collector

voltage

of

Q1I25

drops

to

—5

volts.

This

negative

change

back

biases

D125

and

removes

Q124

as

a

current

source

for

Q145.

The

circuit

is

now

set

for

normal

triggered

operation.

If

a

trigger

pulse

does

not

switch

D105

within

about

60

milliseconds,

the

monostable

circuit

will

reset

itself,

turn

Q124

back

on,

and

free-run

the

sweep.

The

trigger

pulse

that

turned

on

Q125

is

of

short

duration.

Transistor

Q125

would

normally

stay

on

for

the

period

of

the

pulse

width.

However,

C115

(in

the

collector

circuit

of

Q125),

prevents

the

rapid

change

of

voltage.

Instead,

the

RC

voltage

rise

takes

about

60

milliseconds.

At

that

time

D125

becomes

forward

biased

and

the

sweep

free

runs.

Because

of

this

reset

feature

of

the

AUTO.

circuit,

the

sweep

will

not

trigger

at

a

repetition

rate

slower

than

about

15

cps.

The

use

of

Q115

and

Q125

in

a

monostable

mullti-

vibrator

assures

rapid

turn-on

of

Q125.

Single

Sweep

Transistors

Q135

and

Q145

form

a

bistable

multivibrator.

When

the

Single

Sweep

control

is

pushed

to

RESET,

—100

volis

is

applied

through

a

differentiating

network

to

the

base

of

transistor

Q145.

Transistor

Q145

is

biased

into

conduc-

tion,

cutting

off

transistors

Q134

and

Q135

and

biasing

tunnel

diode

D105

at

the

ready

point.

The

cutting

off

of

4-3

Circuit

Description

—

Type

3B3

Q134

removes

the

shunt

path

from

around

the

READY

lamp

B134,

and

B134

lights.

With

the

arrival

of

a

trigger

pulse,

tunnel

diode

D105

is

biased

to

its

high

state

and

triggers

the

Miller

runup

circuit.

As

the

Miller

circuit

runs

up,

the

rising

positive

voltage

is

coupled

back

through

diode

D171

to

the

base

of

Q145,

eventually

cutting

off

Q145.

When

Q145

cuts

off,

diode

D105

drops

to

its

low

state

and

the

sweep

ends.

Also

when

Q145

cuts

off,

QI34

and

Q135

are

per-

mitted

to

conduct.

Transistor

Q134

extinguishes

the

READY

lamp,

and

Q135

keeps

Q145

cut

off until

the

Single

Sweep

control

is

pushed

to

RESET.

Timing

Switch

Timing

in

the

Miller

run-up

circuit

is

determined

by

Timing

Capacitor

C160

charging

through

Timing

Resistor

R160.

Timing

Switch

SW160

selects

the

proper

combination

of

timing

resistor

and

timing

capacitor

for

each

sweep

rate.

In

the

NORM.

position

of

the

MODE

switch,

uncalibrated

variable

sweep

rates

are

available.

If

uncalibrated

sweep

rates

are

desired,

the

VARIABLE

control

(red

knob}

is

turned

away

from

the

CALIBRATED

position.

This

control,

RI60Y,

varies

the

sweep

rate

over

a

2%

to

one

range.

Switch

SW160Y

is

ganged

with

the

VARIABLE

control

in

such

a

way

that

the

UNCALIBRATED

light

comes

on

when

the

control

is

turned

away

from

the

CALIBRATED

position.

CRT

Unblanking

The

electron

beam

in

the

crt

is

unblanked

by

a

negative

waveform

coupled

from

the

plate

of

V194A

through

pin 13

CURRENT

SOURCES

of

the

interconnecting

plug

to

the

blanking

plates

in

the

crt.

The

unblanked

period

coincides

with

the

time

that

tunnel

diode

D105

is

in

its

high

state

(sweep

period).

When

D105

switches

to

its

high

state,

Q114

turns

on

and

a

negative

pulse

from

its

collector

is

applied

to

the

base

of

Q182.

This

transistor

is

connected

as

an

emitter

follower

and

the

negative

pulse

passes

to

the

MODE

switch.

From

the

MODE

switch

it

passes

to

the

base

of

Q194,

where

it

is

amplified

and

coupled

to

the

grid

of

V194A.

A

clamp

circuit

(D195

and

R195)

prevents

the

plate

of

V194A

from

dropping

below

+125

volts.

Delayed

Sweep

Trigger

This

circuit

is

almost

identical

to

the

normal

sweep

trigger

circuit

and

the

detailed

description

is

the

same.

The

only

difference

is

the

supply

voltage

for

the

comparator

(Q74

and

@84).

The

+125-volt

supply

is

connected

through

the

MODE

switch

and

is

only

present

in

the

TRIG.

positions

of

this

switch.

In

all

other

positions

of

the

MODE

switch

the

delayed

sweep

trigger

circuit

is

inoperative.

Delayed

Sweep

Generator

The

part

of

this

circuit

that

forms

the

delayed

sweep

ramp

is

the

same

type

as

that

in

the

normal

sweep

genera-

tor

.

The

major

difference

between

the

two

sweep

generators

is

the

method

of

starting

the

sweep.

Transistors

Q235

and

Q245

and

associated

circuit

elements

form

a

bistable

flip-flop.

With

the

MODE

switch

in

the

+125

A

100

k

45k

No.

1

18k

+125

AUTO

O~@—O

No.

3

———.

on

;

DS

|

Q124

60

MSEC

HOLD

~~

v

Q125

may

be

considered

as

a

switch

controlled

by

trigger

pulses

from

T101.

Q145

D105

Fig.

4-4.

Simplified

drawing

showing

current

sources

for

Q145

in

AUTO

mode.

Tektronix 3B3 User manual

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