Tektronix 3177 User manual

INSTRUCTION

MIAN

UAL

TYPE

3177

SAMPLING

SWEEP

UNIT

Tektronix,

Inc.

S.W,

Millikan

Way

@

P.O.Box

500

@

Beaverton,

Oregon

@

Phone

MI

4-0161

@

Cables:

Tektronix

070-333

763

Type

3177

WARRANTY

All

Tektronix

instruments

are

warranted

against

defective

materials

and

workman-

ship

for

one

year.

Tektronix

transformers,

manufactured

in

our

own

plant,

are

war-

ranted

for

the

life

of

the

instrument.

Any

questions

with

respect

to

the

war-

ranty

mentioned

above

should

be

taken

up

with

your

Tektronix

Field

Engineer.

Tektronix

repair

and

replacement-part

service

is

geared

directly

to

the

field,

there-

fore

all

requests

for

repairs

and

replace-

ment

parts

should

be

directed

to

the

Tek-

tronix

Field

Office

or

Representative

in

your

area,

This

procedure

will

assure

you

the

fastest

possible

service.

Please

include

the

instrument

Type

and

Serial

number

with

all

requests

for

parts

or

service.

Specifications

and

price

change

priv-

ileges

reserved.

Copyright

©)

1963

by

Tektronix,

Inc.,

Beaverton,

Oregon.

Printed

in

the

United

States

of

America.

All

rights

reserved.

Contents

of

this

publication

may

not

be

re-

produced

in

any

form

without

permission

of

the

copyright

owner.

http://manoman.sghill.com

Type

3177

TYPE

3777

SAMPLING

SWEEP

nes

VARIABLE

SITION

TIME/DIV.

oO

ADJ

5

uSEC

2

1

HORIZ.

DOTS

UNCAI

MAG

PER

DIV,

@

x10

é

TRIGGER

ee

=

sensiriviry

|

MANUAL

SCAN

OR

EXT

ATTEN,

SWEEP

MODE

NORMAL

pds

han

MANUAL

RECOVERY

TIME

SINGLE

DISPLAY

RESET

SWEEP

OUTPUT

™’

iv,

OV

(10

KA)

The

Type

3T77

Sampling

Sweep

Unit.

SECTION

1

CHARACTERISTICS

General

Information

The

Type

3177

Sampling

Sweep

Plug-In

Unit

is

designed

for

use

with

all

Tektronix

Type

560-Series

Oscilloscopes

except

the

Type

560

and

Type

565.

The

Type

3177

is

equipped

to

drive

a

digital

unit

in

the

Type

567

Readout

Oscilloscope.

The

Type

3177

must

be

inserted

into the

right-hand

plug-

in

compartment

of

the

oscilloscope

and

a

vertical

sampling

plug-in

unit

(such

as

the

Type

3876)

must

be

inserted

into

the

left-hand

plug-in

compartment

to

complete

the

composite

sampling

system.

Equivalent

Sweep

Rates

Variable

in

fifteen

steps

from

0.2

nsec/div

to

10

usec/div

(0.02

nsec/div

to

1

«sec/div

with

HORIZ.

MAG.

switch

at

X10).

Accuracy

typically

within

1%,

and

in

all

cases

within

3%

of

the

indicated

sweep

rate

with

HORIZ.

MAG.

switch

at

X1.

With

HORIZ.

MAG.

switch

at

X10,

accuracy

is

within

5%.

The

sweep

rate

at

any

given

setting

of

the

TIME/DIV.

switch

can

be

increased

by

about

3

times

with

the

VARIABLE

control.

Samples

Per

Division

10/div

or

100/div.

External

Triggering

Pulse

Repetition

Rate:

Up

to

3

&

10°

pulses/second

(300

megacycles}.

Trigger

circuitry

counts

down

to

a

maximum

sampling

rate

of

about

100

kilocycles/second.

Minimum

Pulse

Amplitude

and

Width:

10

millivolts,

peak-

to-peak,

with

at

least

a

2-nanosecond

width.

With

larger

pulse

amplitudes

(up

to

800

millivolts)

minimum

pulse

width

decreases.

Overload

damage

occurs

at

5

volts

and

above.

Sinusoidal

Frequency

Range:

100

kilocycles

to

300

mega-

cycles;

10

to

800

millivolts

amplitude.

Low

Frequency

Response

(to

trigger

pulses}:

300

kilo-

cycles

(3-db

down

point).

Jitter:

50

picoseconds

or

0.001%

fast

ramp

duration,

whichever

is

greater

(for

50-millivolt

amplitude,

2-nano-

second

width

pulses

with

a

repetition

rate

less

than

10

megacycles},

Jitter

increases

as

pulse

amplitude

and/or

width

decreases

when

repetition

rates

exceed

10

mega-

cycles.

Internal

Triggering

Same

characteristics

as

External

Triggering

but

modified

by

vertical

plug-in

unit

used.

When

used

with

the

Type

3876,

all

characteristics

are

the

same

except

five

times

more

amplitude

is

required

at

the

Type

3876

INPUT

A

or

INPUT

B

connectors

and

the

low-frequency

response

is

3-db

down

at

450

kilocycles.

External

Sweep

Input

Sensitivity:

Adjustable

from

5

to

25

volts

per

horizontal

division

(50

volts

required

for

a

full

10-division

display,

250

volts

maximum).

Input

Resistance:

28

to

100

kilohms,

depending

on

setting

of

EXT.

ATTEN.

control.

Sweep

Output

Amplitude:

1

volt/div

from

a

source

impedance

of

10

kilohms.

Delay

Variable

through

100

nsec.

Mechanical

Construction:

Aluminum

alloy

chassis.

Finish:

Photo-etched,

anodized

front

panel.

Weight:

5

pounds.

Accessories

Supplied

With

the

Type

3177

Tektronix

Part

Number

2

500,

10-nsec

cables

(017-501)

RG-58/AU

with

General

Radio

connectors.

1

Adapter,

BNC-to-GR

(017-025)

1

Adapter,

male

BNC-to-female

(103-032)

UHF

2

Attenuators,

1OXT,

509

with

(017-044)

GR

connectors

2

Instruction

manuals

(070-333}

1-1

Operating

Instructions

—

Type

3177

f

TYPE

31777

SAMPLING

SWEEP

VARIABLE

Beet

eye

TIME/DIV.

GAIN

ADJ.

5

nSEC

2

1

HORIZ.

DOTS

UNCAL

MAG.

PER

DIV.

.

2

@

X10

|

10

7—-

TRIGGERS

SENSITIVITY

x1

MANUAL

SCAN

OR

EXT.

ATTEN.

SWEEP

MODE

MANUAL NORMAL

=

100

nSEc

RECOVERY

TIME

SINGLE

DISPLAY

]

RESET

/

=

y

_

+

EXT.

@

‘)

SWEEP

~

j

INPUT

OUTPUT

iv/DIV.

(10

Kn)

:

.

j

J

SERIAL

7

'

TEKTRONIX.

INC.

PORTLAND,

OREGON,

U.S.A.

Fig.

2-1.

Front

panel

of

the

Type

3177.

2-0

SECTION

2

OPERATING

INSTRUCTIONS

Introduction

The

Type

3177

Sampling

Sweep

Plug-In

Unit

(with

a

ver-

tical

sampling

plug-in

unit)

equips

any

Type

561A,

RM561A,

564, 567,

or

RM567

Oscilloscope

for

sampling-type

opera-

tion.

Front-panel

operation

of

the

Type

3177

resembles

that

of

non-sampling

(real

time}

time-base

units.

This

section

of

the

manual

covers

the

operation

of

the

front-pane!l

controls

and

connectors

(see

Fig.

2-1).

Function

of

Front-Panel

Controls

and

Connectors

POSITION

Conirol

Positions

the

display

horizontally.

HORIZ.

MAG.

Switch

Selects

X1

or

X10

horizontal

display

magnification.

DOTS

PER

DIV.

Switch

Selects

either

10

or

100

samples

per

division.

SWEEP

MODE

Switch

NORMAL

position:

Permits

automatic

dot-by-dot

advance-

ment

through

the

oscilloscope

display.

SINGLE

DISPLAY

position:

Permits

one

display

after

the

RESET

button

is

pressed.

(Useful

for

photographing

the

display.)

-++EXT.

SWEEP

INPUT

position:

Permits

control

of

the

scanning

function

with

an

external

voltage.

MANUAL

position:

Permits

manual

dot-by-dot

advance-

ment

through

the

display

by

turning

the

MANUAL

SCAN

control.

(For

recorder

applications.)

MANUAL

SCAN

OR

EXT.

ATTEN.

Control

Provides

an

internal

semi-intergated,

variable

voltage

for

scanning

when

the

SWEEP

MODE

switch

is

in

the

MANUAL

position,

and

serves

as

a

variable

attenuator

when

the

SWEEP

MODE

switch

is

in

the

+EXT.

SWEEP

INPUT

position.

+EXT.

SWEEP

INPUT

Connector

For

applying

an

external

scanning

voltage.

Sensitivity

variable

from

5

to

25

volts/div;

input

impedance

variable

from

28

to

100

kilohms.

Maximum

input

voltage

250

volts,

peak.

SWEEP

OUTPUT

Connector

For

monitoring

the

sweep

voltage.

(Output

variable

trom

about

3.5vde

to

about

15

vde;

I-volt

change

equals

1

division

of

horizontal

deflection

with

10-kilohm

source

impedance.)

TRIG.

OUT

Connector

For

externally

monitoring

a

positive

trigger

pulse

after

each

trigger

event.

The

pulse

width

is

at

least

0.4

micro-

second

at

0.15-volt

amplitude.

®

EXT.

INPUT

Connector

For

applying

an

external

trigger.

Input

impedance:

50

ohms

shunted

by

12

microhenries.

INT.-EXT.

Switch

Selects

either

an

internal

trigger

(INT.

position)

from

the

vertical

plug-in

unit,

or

an

external

trigger

(EXT.

position)

from

the

EXT.

INPUT

connector,

and

determines

whether

triggering

takes

place

on

the

positive

(+)

or

negative

(—)

slope

of

the

input

signal.

DELAY

Control

Allows

the

start

of

the

display

to

be

varied

through

100

nanoseconds

with

respect

to

the

trigger

event.

TRIGGER

SENSITIVITY

Control

Varies

the

sensitivity

of

the

triggering

circuit.

Also

causes

the

trigger

circuit

to

free-run

when

turned

fully

clockwise.

RECOVERY

TIME

Control

Varies

the

holdoff

time

of

the

trigger

circuits

to

assure

stable

triggering.

TIME/DIV.

Switch

Sets

the

equivalent

sweep

rate

of

the

display.

VARIABLE

Control

Varies

the

sweep

rate

(uncalibrated)

between

TIME/DIV.

steps.

The

equivalent

sweep

rate

at

any

given

setting

of

the

TIME/DIV.

switch

can

be

increased

about

3

times.

GAIN

ADJ.

(a

front-panel

screwdriver

adjustment)

Adjusts

gain

to

match

oscilloscope

deflection

factor.

Installing

the

Type

3177

into

the

Oscilloscope

CAUTION

Turn

off

oscilloscope

power

while

inserting

or

removing

plug-in

units.

Otherwise,

power

supplies

in

the

oscilloscope

may

fail

to

regulate

momen-

tarily

as

plug-in

units

are

removed

or

replaced.

The

Type

3177

is

designed

to

drive

the

horizontal

de-

flection

plates

of

the

crt;

it

must

be

used

in

the

right-hand

plug-in

compartment.

When

inserting

the

Type

3177

into

the

plug-in

compartment,

first

check

that

the

latch

at

the

bottom

of

the

front

panel

is

in

a

horizontal

position.

Then

make

sure

the

interconnecting

plugs

are

properly

aligned.

The

Type

3177

should

then

slip

easily

into

the

compartment.

Once

the

plug-in

has

been

properly

seated,

turn

the

aluminum

knob

of

the

plug-in

unit

a

few

turns

clockwise

until

it

is

hand-tight.

To

remove

the

plug-in

unit,

turn

the

aluminum

knob

counterclockwise

as

far

as

it

will

go

and

pull

the

plug-in

unit

straight

out.

2-1

Operating

Instructions

—

Type

3177

Displaying

a

Signal

The

following

procedure

covers

first-time

operation

of

the

Type

3177.

It

will

enable

you

to

display

a

signal

on

the

ert.

Use

this

procedure

in

conjunction

with

the

vertical

plug-in

unit

instructions.

1.

Set

the

Type

3777

front-panel

controls

as

follows:

POSITION

Midrange

TIME/DIV.

5

nSEC

VARIABLE

CALIB.

DELAY

Fully

counterclockwise

TRIGGER

SENSITIVITY

Fully

counterclockwise

HORIZ.

MAG.

Xl

DOTS

PER

DIV.

100

SWEEP

MODE

NORMAL

INT.-EXT.

INT.

{Set

to

polarity

of

signal

you

wish

to

observe)

RECOVERY

TIME

2.

Insert

the

Type

3177

into

the

right-hand

plug-in

com-

partment

of

the

oscilloscope

and

the

vertical

sampling

plug-

in

unit

into

the

left-hand

compartment.

Turn

on

the

oscillo-

scope

power

and

allow

a

few

minutes

for

warm-up.

Fully

counterclockwise

3.

Apply

the

signal

you

wish

to

observe

to

the

input

connector

of

the

vertical

sampling

plug-in

unit.

(Note:

Make

sure

the

signal

meets

the

triggering

requirements

described

in

Section

1.}

4.

Slowly

advance

the

TRIGGER

SENSITIVITY

control

for

a

stable

display.

The

RECOVERY

TIME

control

may

also

help

stabilize

the

display.

5.

Set

the

TIME/DIV.

switch

to

the

position

where

the

displayed

signal

covers

the

desired

amount

of

horizontal

graticule

divisions.

6.

With

the

POSITION

control,

move

the

display

hori-

zontally

to

the

desired

point

on

the

graticule.

7.

Turn

the

DELAY

control

and

notice

its

effect

on

the

display.

The

action

of

the

DELAY

control

is

most

significant

at

faster

sweep

rates.

The

DELAY

control

varies

the

position

of

the

displayed

pulse

with

respect

to

the

start

of

the

trace.

The

position

of

the

pulse

with

respect

to

the

start

of

the

trace

can

be

varied

100

nanoseconds

with

the

DELAY

control.

8.

Set

the

SWEEP

MODE

switch

to

MANUAL

and

turn

the

MANUAL

SCAN

control.

Note

the

horizontal

scanning

of

the

electron

beam

on

the

crt.

9.

Set the

SWEEP

MODE

switch

to

SINGLE

DISPLAY.

Press

the

RESET

button.

After

pressing

the

RESET

button,

the

Type

3177

allows

one

complete

scan

of

the

electron

beam

across

the

crt.

This

is

particularly

useful

for

photo-

graphing

displays

at

slow

pulse

repetition

rates.

Gain

Adjust

The

basic

oscilloscope

crt

deflection

factor

varies

slightly

from

one

oscilloscope

to

another.

For

this

reason,

the

GAIN

ADJ.

(a

front-panel

screwdriver

adjustment)

should

be

checked

and

adjusted

as

necessary

each

time

the

Type

3177

is

used

in

a

different

oscilloscope.

Also,

check

the

2-2

GAIN

ADJ.

occasionally

during

regular

use

of

the

instru-

ment.

Checking

or

setting

the

GAIN

ADJ.

requires

the use

of

an

accurate

frequency

source,

such

as

the

Tektronix

Type

180A

Time-Mark

Generator.

The

frequency

standard

used

must

have

a

frequency

output

of

at

least

100

kilocycles,

and

preferably

above

1

megacycle.

To

check

or

adjust

the

Type

3T77

GAIN

ADJ.

control,

proceed

as

follows:

1.

Insert

the

Type

3T77 and

the

associated

vertical

sampling

plug-in

unit into

the

oscilloscope,

turn

on

the

power

and

allow

the

instrument

to

warm

up

for

at

least

2

minutes

before

proceeding.

2.

Set

the

front-panel

controls

of

the

Type

3177

as

follows:

POSITION

Midrange

DOTS

PER

DIV.

100

TRIGGER

SENSITIVITY

Fully

clockwise

VARIABLE

CALIB.

SWEEP

MODE

NORMAL

HORIZ.

MAG.

X]

INT.-EXT.

+

INT.

Other

controls

may

be

set

to

any

position.

3.

From

an

accurate

frequency

source,

apply

a

signal

to

the

Input

connector

of

the

vertical

sampling

plug-in

unit

and

adjust

for

a

vertical

deflection

of

2

to

6

divisions.

4.

Determine

the

time

duration

of

one

cycle

of

the

signal

from

the

frequency

source

{time

duration

of

one

cycle

(in

seconds)

is

the

reciprocal

of

the

frequency

{in

cycles

per

second)

).

5.

Set

the

TIME/DIV.

switch

for

a

sweep

rate

that

will

display

one-half

to

one

cycle

of

the

applied

signal

per

division

of

deflection.

6.

Set

the

TRIGGER

SENSITIVITY

and

RECOVERY

TIME

controls

for

a

stable

display.

7.

Check

for

the

proper

number

of

cycles

per

division.

If

the

number

of

cycles

per

division

does

not

exactly

agree

with

the

setting

of

the

TIME/DIV.

switch,

set

the

GAIN

ADJ.

for

the

proper

timing.

Use

the

POSITION

control

to

align

the

display

with

the

graticule

markings.

Triggering

the

Type

3177

The

Type

3T77

can

be

triggered

either

internally

or

externally.

Internal

triggering

requires

no

signal

connections

to

the

Type

3777

since

the

triggering

signal

is

coupled

internally

from

the

vertical

sampling

plug-in

unit.

However,

external

triggering

is

more

sensitive

(see

Section

1).

External

triggering

is

also

independent

of

the

displayed

waveform.

Thus,

when

signals

of

different

amplitudes

are

applied

to

the

vertical

plug-in

unit,

the

triggering

controls

do

not

require

resetting

for

a

stable

display.

However,

an

external

triggering

signal

must

be

time

to

the

displayed

signal

to

maintain

stable

triggering.

The

+

and

—

positions

of

the

INT.-EXT.

switch

determine

whether

triggering

takes

place

on

the

positive-

or

negative-

@l

going

slope

of

the

triggering

signal.

The

INT.

or

EXT.

posi-

tions

determine

whether

the

triggering

signal

comes

from

the

vertical

sampling

plug-in

unit

or

from

the

EXT.

INPUT

connector.

Selecting

the

Equivalent

Sweep

Rate

The

Type

31777

TIME/DIV.

switch

selects

equivalent

sweep

rates

from

0.2

nanosecond

per

division

to

10

micoseconds

per

division.

These

rates,

in

turn,

provide

an

equivalent

10-

division

display

width

from

2

nanoseconds

to

100

micro-

seconds.

Setting

the

HORIZ.

MAG.

switch

to

X10 increases

the

equivalent

sweep

rate

10

times

at

any

setting

of

the

TIME/DIV.

switch.

This

expands

the

display

in

both

direc-

tions

from

the

center

graticule

division

to

cover

the

entire

graticule

(horizontally).

The

VARIABLE

control

increases

the

equivalent

sweep

rate

at

any

setting

of

the

TIME/DIV.

switch

about

3

times

(uncalibrated)

when

the

control

is

fully

clockwise.

Selection

of

sweep

rate

depends

on

the

duration

of

the

applied

signal

and

the

specific

portion

of

the

signal

you

wish

to

observe.

The

DELAY

control

aids

in

observing

a

specific

portion

of

the

applied

signal.

The

equivalent

sweep

rates

of

the

Type

3777

are

accurate

within

3%

of

the

TIME/DIV.

control

setting

when

the

VARI-

ABLE

control

is

set

to

CALIB.

and

the

HORIZ.

MAG.

switch

is

set

to

X1.

This

permits

accurate

time

measurements

di-

rectly

from

the

oscilloscope

display.

Selecting

the

Dots

Per

Division

In

a

sampling

system,

the

applied

signal

is

displayed

as

a

series

of

dots

distributed

across

the

ert.

With

a

greater

number

of

dots

in

the

display,

the

trace

appears

more

con-

tinuous.

With

less

dots

in

the

display,

there

is

less

continu-

ity

in

the

trace

and

the

individual

dots

become

more

apparent

(see

Fig.

2-2).

The

DOTS

PER

DIV.

switch

selects

either

10

dots

per

division

or

100

dots

per

division.

Proper

setting

of

the

DOTS

PER

DIV.

switch

is

a

choice

between

good

trace

continuity

and

flicker.

Flicker

will

become

ap-

parent

with

signals

of

low

repetition

rate

when

the

DOTS

PER

DIV.

switch

is

set

to

100.

By

changing

the

setting

of

the

DOTS

PER

DIV.

switch

to

10,

flicker

will

become

less

apparent.

However,

with

10

dots

per

division,

make

sure

the

SMOOTH-NORMAL

switch

of

the

vertical

sampling

plug-in

unit

is

set

to

NORMAL.

Otherwise,

the

display

may

be

distorted.

Signals

with

fast

repetition

rates

cause

less

flicker;

thus

the

DOTS

PER

DIV.

switch

may

be

set

to

100

for

best

trace

continuity.

When

making

time

measurements

from

the

crt,

the

indi-

vidual

dots

can

serve

as

time

markers.

For

example,

suppose

the

Type

3177

TIME/DIV.

switch

is

set

to

1

nSEC

and

the

DOTS

PER

DIV.

switch

is

set

to

10.

In

this

case,

each

dot

@i

Operating

Instructions

——

Type

3177

4

+

*e,

*,

+

.

>

.

*

+

.

,

ji

aa

.

eee eee

SSS

ES

SESS

SS

SSSR

SEER

SER

SESE

Eee

eee

TrvTyrrer

TT

Tere

Rrergrrre

TUT

TTT

rTrTrypserre

. .

7

hal

.

+

. :

>

°:

‘

es

y

os

ere

een'

(a)

=

TIT

TTT

Tyr

tt

SEE

Ree

SaaS

ea

eeee

TTT

+

tipi

THT

+

a:

a

+

N

arn

nenie

A

\

4)

(b)

Fig,

2-2.

(a)

A

typical

display

with

the

DOTS

PER

DIV.

switch

set

to

10.

(b)

The

same

signal

with

the

DOTS

PER

DIV.

switch

set

to

100.

represents

0.1

nanosecond

in

equivalent

time

(1

nanosecond

per

division

divided

by

the

10

dots

per

division).

This

application

is

easiest

when

the

display

contains

10

dots

per

division

(i.e.,

the

DOTS

PER

DIV.

switch

must

be

set

to

10

or

the

HORIZ.

MAG.

switch

must

be

set

to

X10).

Under

certain

conditions

it

is

possible

to

get

a

false

display

when

using

a

sampling-type

system.

This

happens

when

certain

relationships

exist

between

the

frequency

of

the

applied

signal

and

the

equivalent

time

between

dots.

A

false

display

can

be

detected

by

changing

the

setting

of

the

DOTS

PER

DIV.

switch

or

the

TIME/DIV.

switch.

With

a

valid

display,

a

change

in

the

equivalent

time

between

dots

should

not

affect

the

displayed

waveform.

However,

if

the

display

is

false,

it

will

change

in

apparent

repetition

rate

or

disappear

when

the

equivalent

time

per

dot

changes.

2-3

SECTION

3

APPLICATIONS

The

procedures

in

this

section

describe

some

basic

applications

for

the

Type

3177.

Time

and

Frequency

Measurements

The

Type

3177

is

accurately

calibrated

to

indicate

equiva-

lent

time

per

division

along

the

horizontal

axis

of

the

oscilloscope

display.

Thus,

the

following

procedures

concern

measuring

time

and

frequency

of

electrical

events.

Time

Duration.

To

measure

the

time

duration

of

an

electrical

event,

proceed

as

follows:

1.

Obtain

a

stable

display

of

the

event

you

wish

to

measure.

2.

Set

the

TIME/DIV.

switch

so

the

distance

between

the

two

points

you

wish

to

measure

covers

a

large

portion

of

the

graticule.

3.

To

get

the

time

duration,

count

the

number

of

grati-

cule

divisions

between

the

two

points,

multiply

by

the

TIME/

DIV.

switch

setting,

then

divide

the

result

by

the

HORIZ.

MAG.

switch

setting.

To

illustrate

this

procedure,

assume

the

TIME/DIV.

switch

is

set

to

5nSEC

and

the

HORIZ.

MAG.

switch

to

X1.

Then,

assume

the

distance

between

the

two

points

on

the

display

is

4.8

major

graticule

divisions.

Thus,

the

time

duration

would

be

4.8

divisions

multiplied

by

5

nanoseconds/divi-

sion

(TIME/DIV.

switch

setting),

or

24

nanoseconds,

Risetime.

The

risetime

of

a

pulse

is,

by

definition,

the

time

required

for

the

pulse

to

rise

from

10%

to

90%

of

2.2

div.

or

.44

nsec

—

!

"TT

90%

f

point

TTTETT

TTT

TAT

TY

Ty

10%

point

+t

ttt

HH

i

Pitisi

ris

tig

4

4+

tt

4+

+

.2

nsec/div.

Fig.

3-1.

Determining

pulse

risetime.

®

its

maximum

amplitude.

To

measure

pulse

risetime

or

fall-

time

proceed

as

follows:

1.

Set

the

TIME/DIV.

switch

and

the

DELAY

control

to

display

the

leading

edge

of

the

pulse.

(Or,

for

falltime

measurement,

display

the

falling

edge.)

For

best

accuracy,

the

rising

portion

of

the

pulse

should

span

at

last

two

horizontal

graticule

divisions.

2.

Set

the

vertical

plug-in

unit

so

the

display

covers

two

to

eight

vertical

graticule

divisions.

3.

Measure

the

horizontal

distance

between

the

10%

and

90%

amplitude

points

on

the

waveform.

See

Fig.

3-1.

4.

The

risetime

is

the

number

of

divisions

in

step

3

multi-

plied

by

the

setting

of

the

TIME/DIV.

switch

(divided

by

the

HORIZ.

MAG.

switch

setting).

Frequency

or

Repetition

Rate.

Frequency

or

repetition

rate

is

the

number

of

complete

electrical

events

occurring

in

a

second.

To

measure

the

frequency

or

repetition

rate

of

the

displayed

signal

in

cycles

(or

pulses}

per

second,

pro-

ceed

as

follows:

1.

Find

the

time

duration

of

a

complete

event

as

described

under

‘Time

Duration’.

2.

The

frequency

or

repetition

rate

of

the

applied

signal

is

the

reciprocal

of

step

1.

To

illustrate

this

procedure,

assume

the

TIME/DIV.

switch

is

set

to

20nSEC

and

the

HORIZ.

MAG.

switch

to

X10.

Then,

assume

one

event

covers

6.4

major

graticule

divisions.

Thus,

the

frequency

or

repetition

rate

would

be

6.4

divisions

multiplied

by

20

nanoseconds/division

(TIME/DIV.

switch

setting)

divided

by

10

{the

HORIZ.

MAG.

switch

setting),

or

12.8

nanoseconds.

The

frequency

is

then

the

reciprocal

of

12.8

nanoseconds,

or

about

78.1

megacycles.

An

alternative

method

for

measuring

frequency

or

repeti-

tion

rate

is

as

follows:

1.

Set

the

TIME/DIV.

switch

for

a

2-

to

10-cycle

display

of

the

input

signal.

2.

Count

the

exact

number

of

cycles

(including

fractional

cycles)

occurring

in

10

major

graticule

divisions.

3.

Multiply

the

number

of

cycles

obtained

in

step

2

by

the

Frequency

Multiplier

value

opposite

the

appropriate

TIME/DIV.

switch

setting

in

Table

3-1.

TABLE

3-1

TIME/DIV.

Setting

|

Frequency

Multiplier

1

nSEC

100mc™

10

nSEC

10

mc

1

SEC

1

me

1

»SEC

100

ke

10

wSEC

10

ke

Applications

—

Type

3177

Single

Display

Mode

The

Type

3177

has

a

RESET

button

that

provides

a

single

display

of

the

signal.

This

feature

is

helpful

for

taking

photographs

of

low

repetition-rate

signals

when

the

actual

sweep

rate

is

slow.

With

the

SINGLE

DISPLAY

feature,

it

is

easy

to

obtain

even

exposure

over

a

photograph.

Without

SINGLE

DISPLAY,

it

is

necessary

to

take

a

time

exposure

to

minimize

the

effects

of

interaction

between

shutter

time

and

the

instantaneous

location

of

the

scanning

beam.

To

use

the

SINGLE

DISPLAY

feature,

set

up

the

Type

3177

for

a

normal

triggered

display

with

the

SWEEP

MODE

switch

set

to

NORMAL.

Then

set

the

SWEEP

MODE

switch

to

SINGLE

DISPLAY.

Push

the

RESET

button,

and

the

ert

beam

will

produce

a

single

display.

To

make

a

photographic

recording

of

the

single

display,

open

the

camera

shutter,

press

the

RESET

button

and,

after

allowing

sufficient

time

for

a

complete

display,

close

the

camera

shutter.

Consult

the

camera

instruction

manual

for

further

information

on

photographic

recording.

Paper

Recorder

Operation

The

voltage

at

the

SWEEP

OUTPUT

connector

provides

a

convenient

source

for

controlling

the

X

or

T

(time)

axis

of

a

paper

recorder.

The

SWEEP

OUTPUT

connector

supplies

a

total

open-circuit

voltage

change

of

10

volts

(+3.5

volts

to

about

+13.5

volts)

when

the

electron

beam

sweeps

the

full

10

horizontal

graticule

divisions

(one

volt

per

division).

Source

impedance

of

the

SWEEP

OUTPUT

connector

is

10

kilohms.

When

the

SWEEP

MODE

switch

is

set

to

MANUAL,

the

voltage

at

the

SWEEP

OUTPUT

connector

is

set

by

the

MAN-

UAL

SCAN

control.

The

MANUAL

Sweep

Mode

allows

manual

control

of

horizontal

scanning.

In

recorder

opera-

tion,

this

permits

operation

with

slow

response

recorders.

+Ext.

Sweep

Input

Mode

In

this

mode

of

operation,

an

external

sweep

voltage

may

be

used

to

control

horizontal

scanning

in

the

sampling

system.

To

do

this,

the

externally

applied

sweep

voltage

must

swing

between

zero

and

at

least

+50

volts

for

a

3-2

horizontal

deflection

of

10

divisions.

The

EXT.

ATTEN.

con-

trol

provides

for

signals

that

have

peak

amplitude

to

+250

volts.

This

feature

is

useful

in

recorder

applications

where

the

recorder

has

its

own

sweep

voltage

and

a

sweep

output.

In

such

a

case,

the

sweep

output

of

the

recorder

is

used

as

the

scanning

voltage

for

the

Type

3177.

Then,

the

verti-

cal

(or

Y

axis)

information

is

coupled

to

the

recorder

from

the

vertical

sampling

plug-in

unit.

Since

most

conventional

oscilloscopes

have

a

sweep

cut-

put,

a

monitoring

oscilloscope

can

be

used

in

this

applica-

tion

as

a

“slave”

in

place

of

a

recorder.

To

use the

+Ext.

Sweep

Input

Mode

for

a

recorder

or

“slave”

oscilloscope

application,

proceed

as

follows:

1.

Set

the

SWEEP

MODE

switch

to

NORMAL

and

obtain

a

stable

display

of

the

applied

signal.

2.

Connect

the

sawtooth

of

the

‘‘slave’’

oscilloscope

or

recorder

to

the

--EXT.

SWEEP

INPUT

connector.

3.

Set

the

SWEEP

MODE

switch

to

--EXT.

SWEEP

INPUT.

4.

Connect

the

vertical

amplifier

output

signal

to

the

vertical

input

connector

of

the

“slave”

oscilloscope

or

recorder.

5.

Set

the

triggering

controls

of

the

“slave”

oscilloscope

for

a

free-running

display,

or

initiate

the

recorder

motion.

6.

For

the

‘“‘slave’’

oscilloscope,

select

a

slow

sweep

which

produces

a

well

defined

display

on

both

oscilloscopes.

7.

Set the

EXT.

ATTEN.

control

(red

knob

concentric

with

SWEEP

MODE

switch)

so

that

10

divisions

of

horizontal

deflection

on

the

sampling

oscilloscope

matches

the

desired

divisions

on

the

“slave”

oscilloscope

or

recorder.

As

long

as

the

EXT.

ATTEN.

control

is

adjusted

for

10

divisions

of

horizontal

deflection

on

both

instruments,

the

equivalent

sweep

rates

are

the

same

as

the

Type

3177

TIME/DIV.

switch

setting.

For

example,

if

the

EXT.

ATTEN.

control

is

set

for

5

divisions

of

sampling

oscilloscope

deflec-

tion,

the

equivalent

sweep

rate

of

the

‘slave’

oscilloscope

is

one-half

the

numerical

setting

of

the

Type

3177

TIME/DIV.

switch.

Thus,

a

decrease

in

horizontal

deflection

on

the

sampling

oscilloscope

results

in

an

increase

in

the

equivalent

sweep

rate

of

the

conventional

oscilloscope

or

recorder.

SECTION

4

CIRCUIT

DESCRIPTION

General

Operation

The

Type

3177

contains

four

main

circuits:

the

Trigger

and

Holdoff

circuit,

the

Fast

Ramp

circuit,

the

Staircase

Generator

circuit,

and

the

Horizontal

Amplifier.

The

Type

3177

provides

horizontal

deflection

potentials

to

the

crt.

In

addition,

it

controls

the

exact

time

that

the

vertical

plug-in

unit

samples

the

applied

signal.

The

follow-

ing

discussion

describes

the

basic

technique

involved.

Basic

Sampling

Technique

To

recreate

a

repetitive

signal

using

the

sampling

tech-

nique,

samples

must

be

taken

over

the

portion

of

the

signal

VERTICAL

PLUG-IN

UNIT

you

wish

to

display.

When

sampling

a

fixed

point

on

a

waveform,

a

trigger

circuit

trips

the

sampling

gate

in

the

vertical

system

and

allows

a

sample

of

the

incoming

signal

to

pass

through.

A

block

diagram

of

this

system

appears

in

Fig.

4-1.

In

actual

practice,

the

system

shown

in

Fig.

4-1

could

not

take

a

sample

on

the

leading

edge

of

the

signal

be-

cause

of

the

finite

time

delay

in

the

Trigger

circuit.

There-

fore,

if

a

delay

is

introduced

in

the

input

circuit

of

the

vertical

system,

the

Trigger

circuit

will

have

time

to

open

the

sampling

gate

in

the

vertical

system

just

as

the

leading

edge

of

the

incoming

signal

reaches

the

gate.

Fig.

4-2

shows

a

block

diagram

with

a

delay

circuit

added

in

the

vertical

system.

SAMPLING

>

°

GATE

VERTICAL

AMPLIFIER

TRIGGER

CIRCUIT

ee

Nh

LA,

Fig.

4-1.

Circuit

required

for

sampling

at

a

fixed

point

on

an

input

signal.

VERTICAL

PLUG-IN

UNIT

in

ees

vwveseSeS-

350

36.6.

aa

8S

=

~”

|

JL

|

i

DELAY

SAMPLING

VERTICAL

|

CRT

LINE

~

GATE

AMPLIFIER

}

=

|

Te

|

\

|

Po

5

ee

|

>

TRIGGER

|

CIRCUIT

aN

4

Fig.

4-2.

Delay

line

added

to

the

circuit

of

Fig.

4-1

so

sampling

takes place

on

the

leading

edge

of

the

input

signal.

4-1

Circuit

Description

—

Type

3177

F

|

-_——

VERTICAL

PLUG-IN

UNIT

VERTICAL

AMPLIFIER

|

{

DELAY

SAMPLING

>

|

LINE

~

|

TRIGGER

~

VARIABLE

CIRCUIT

id

O-

+

NS

S77

Fig.

4-3.

Variable

delay

circuit

added

so

sampling

takes

place

at

various

points

on

the

input signal.

VERTICAL

PLUG-IN

UNIT

| |

| I

|

SAMPLE

|

DELAY

SAMPLING

ENVELOPE

VERTICAL

|

LINE

GATE

DETECTOR

AMPLIFIER

|

(MEMORY)

|

=

| \

Noe

LL

LLL

I

“

|

ai

rae

~

|

FAST

RAMP

|

TRIGGER

_

And

TRIGGER

STAIRCASE

HORIZONTAL

|

CIRCUIT

COMPARATOR

REGENERATOR

GENERATOR

AMPLIFIER

|

CIRCUIT

n

| !

|

'

|

<

|

5

a

|

TYPE

3177

4-2

Fig.

4-4.

Complete

block

diagram

of

the

sampling

system.

Although

the

system

represented

in

Fig.

4-2

could

sample

an

incoming

signal

at

one

point

on

its

leading

edge,

it

could

not

sample

the

signal

over

its

entire

duration.

Instead,

it

would

consistently

sample

the

same

point

on

the

signal

each

time

it

was

triggered.

In

order

to

sample

over

the

entire

duration

of

the

signal,

a

varying

delay

must

be

introduced

so

the

samples

can

be

taken

at

various

points

on

the

signal.

This

system

would

resemble

Fig.

4-3.

The

variable

delay

we

introduce

must

produce

fairly

long

delays

(up

to

0.1

millisecond)

and

must

continuously

vary

the

amount

of

delay.

The

variable

delay

circuit

used

in

the

Type

3177

produces

an

electronic

delay

by

a

method

called

“trigger

slewing”.

The

trigger

circuit

initiates

a

fast-rising

voltage

ramp

when

triggered

by

the

incoming

signal.

This

ramp

voltage

must

fall to

the

slewing

voltage

level

of

the

comparator,

then

a

new

pulse

(slewed

trigger)

is

generated

to

operate

the

sampling

gate.

How

long

the

slewed

trigger

is

delayed

depends

upon

the

rate

of

the

fast

ramp

and

the

level

of

the

slewing

voltage.

The

slewing

voltage,

and

thus

the

time

delay,

is

directly

proportional

to

horizontal

ert

deflection.

Horizontal

deflection

voltage

and

slewing

voltage

may

be

obtained

manually

but

are

normally

obtained

from

the

Staircase

Generator,

which

automatically

increases

the

voltage

after

each

sample

is

taken.

Thus,

the

sampling

gate

will

open.

slightly

later

and

the

incoming

signal

will

be

sampled

at

a

different

point.

Fig.

4-4

shows

the

improved

sampling

system

with

the

comparator

circuit

replacing

the

variable

delay

block.

In

the

discussion

of

a

sampling

system

the

terms

“real

time”

and

‘‘equivalent

time’

are

often used.

To

understand

the

meanings

of

these

terms,

consider

the

following

case:

lf

we

recreate

a

repetitive

pulse

50

nanoseconds

wide

by

taking

50

samples

{one

sample

per

incoming

pulse)

the

real

time

between

successive

samples

depends

on

the

repetition

rate

of

the

signal.

However,

by

using

50

samples

to

recon-

struct

a

waveform

display,

we

are,

in

effect,

pretending

that

all

of

the

samples

were

taken

from

a

single

input

pulse.

lf

this

were

true,

the

time

between

samples

in

the

example

would

be

one

nanosecond

(50

samples

along

a

50-nano-

“Real

time’

spacing

|

at

Repetitive

|

Sample

taken

Point

on

waveform

where

last

sample

was

taken

_~

Circuit

Description

—

Type

3177

second

pulse).

This

is

the

equivalent

time

between

samples

and

a

10-division

display

would

have

an

equivalent

rate

of

5

nanoseconds

per

division.

Fig.

4-5

illustrates

the

relation-

ship

between

real

time,

equivalent

time,

and

an

input

signal.

CIRCUIT

ANALYSIS

The

basic

operation

of

the

sampling

system

is

covered

previously

in

this

section.

This

portion

of

the circuit

descrip-

tion

contains

a

detailed

discussion

of

each

of

the

major

circuits

of

the

Type

3177.

Refer

to

the

schematics

at

the

rear

of

the

manual

as

you

read

through

this

discussion.

Tunnel

Diodes

Since

tunnel

diodes

are

used

in

several

circuits

of

the

Type

3177,

their

basic

operation

is

discussed

here,

rather

than

under

the

operation

of

a

specific

circuit.

Tunnel

diodes

have

low

inductance

and

capacitance,

and

therefore

make

good

switching

devices.

Fig.

4-6

shows

the

voltage-current

characteristics

of

a

typical

20-ma_

tunnel

diode.

Notice

that

as

the

current

is

increased

from

zero

to

the

20-ma

point,

the

termina!

voltage

increases

slowly

to

about

75

millivolts

(the

“low-voltage”

state).

Then

suddenly,

a

further

increase

in

current

causes

an

abrupt

switch

in

terminal

voltage

to

about

500

millivolts

(the

“high-voltage”

state}.

The

current

must

then

be

reduced

to

about

2ma

to

switch

the

tunnel

diode

from

the

‘high-voltage’

state

back

to

the

“low-voltage”

state.

Trigger

and

Holdoff

Circuit

When

the

Type

3177

is

waiting

to

be

triggered,

tunnel

diodes

D22

and

D42

are

in

the

“low-voltage”

state

and

D25

is

in

its

“high-voltage”

state.

With

D22

in

its

low

state,

there

is

about

+50

millivolts

on

the

base

of

Q24

not

enough

to

turn

it

on.

Q34

and

Q44

are

also

off.

“Equivalent

time’’

spacing

Second

sample

taken

Third

sample

taken

Points

on

waveform

where

were

taken

Fig.

4-5.

Relationship

between

real

time,

equivalent

time,

and

the

input

signal.

4-3

Cirevit

Description

—

Type

3177

“Low-voltage”

state

30

Current

(milliamps)

M@-

8

y4e-------------

ie

High

voltage’

state

Time

200

300 400

500

600

Terminal

Voltage

(millivolts)

Fig.

4-6.

Voltage-current

characteristics

of

a

typical

20-ma

tunnel

diode.

Triggering

is

initiated

by

bringing

D22

from

its

low

state

to

its

high

state.

Therefore,

a

positive-going

signal

is

required

from

the

collector

of

Q14

to

produce

a

trigger.

The

size

of

the

positive

signal

required

to

switch

D22

to

its

high

state

is

determined

by

the

setting

of

SENSITIVITY

control

R19,

and

TRIG.

SENS.

RANGE

adjustment

R21.

A

portion

of

the

input

signal

from

the

vertical

plug-in

unit

is

coupled

to

Q14

for

internal

triggering

via pin

3

of

the

interconnecting

plug.

T5

provides

trigger

slope

selection.

Q1l4

is

a

grounded-base

(non-inverting)

amplifier

with

a

current

gain

of

nearly

1.

A

portion

of

the

Q14

collector

current

passes

through

D22.

When

the

collector current

of

Q14

passes

a

certain

value

set

by

the

SENSITIVITY

control,

D22

switches

to

its

high

state

of

about

+500

millivolts.

This

positive

switching

pulse

from

D22

passes

through

R40

and

C40

to

D42

and

switches

D42

from

its

low

state

to

its

high

state.

The

switching

pulse

of

D42

drives

the

Fast

Ramp

circuit.

The

positive

switching

pulse

from

D22

also

passes

to

the

base

of

Q24

and

turns

it

on,

and

the

collector

voltage

of

Q24

drops

toward

ground.

As

a

result,

D27

turns

on

and

the

increased

drop

across

R26

reduces

the

current

through

D25

and

switches

it

to

its

low

state.

Also,

current

through

D28

increases

the

voltage

drop

across

R22

and

causes

D22

to

return

to

its

low

state.

D22

is

then

held

in

its

low

state

as

long

as

D25

remains

in

its

low

state.

Therefore,

D25

serves

as

a

trigger

holdoff

because

D22

cannot

be

triggered

until

D25

changes

states.

Q34

and

Q44

and

associated

circuitry

hold

D25

in

its

low

state

for

a

period

determined

by

the

time

constant

of

C30,

C31,

R31,

and

RECOVERY

TIME

con-

trol

R30.

The

holdoff

time

is

considerably

greater

than

the

amount

of

equivalent

time

displayed

on

the

crt.

In

the

fast

sweep

rates

it

is

greater

than

10

microseconds

and

increases

to

about

300

microseconds

at

the

slowest

sweep

rate.

4-4

Q24

turns

off

almost

immediately

after

it

is

turned

on.

However,

during

the

time

it

is

turned

on,

C30

and

C31

discharge.

Then,

when

Q24

turns

off,

C30

and

C31

must

charge

through

R30, R31,

and

Q34.

This

charging

current

turns

Q34

on

and

Q34

supplies

current

to

hold

D22

and

D25

in

their

low

state.

Current

through

Q34

also

discharges

C34,

Charging

current

through

C30

stops

when

D3]

becomes

forward

biased,

This

allows

Q34

to

turn

off

and

Q44

to

turn

on

from

the

charging

of

C34

through

R34

and

the

base

of

Q44,

At

the

same

time,

Q34

turns

off

and

allows

current

from

R21

and

R22

to

pass

through

D22.

However,

D22

still

cannot

be

triggered

since

D25

is

still

in

its

low

state.

The

current

through

Q44

holds

D25

in

its

low

state

until

C34

completes

its

charge.

At

this

point,

Q44

will

turn

off

and

allow

more

current

to

pass

through

D25

and

switch

it

to

its

high

state.

D22

can

then

be

triggered

again.

With

R19

set

to

maximum

resistance

(fully

clockwise)

the

circuit

free-runs,

In

this

case,

D22

switches

to

its

high

state

each

time

D25

switches

to

its

high

state

following

the

holdoff

period.

Fast

Ramp

This

circuit

generates

a

fast-ramp

waveform,

compares

it

with

an

existing

slow-ramp

voltage

from

the

Staircase

Generator,

and

produces

a

positive-polarity

slewed

pulse.

The

fast-ramp

waveform

is

developed

across

Ramp

Slope

Capacitor

C88.

Comparison

with

the

slow-ramp

waveform

takes

place

at

Q93.

The

slewed

pulse

is

generated

at

D93

and

appears,

inverted

and

amplified,

at

the

collector

of

Q94,

The

positive

trigger

from

the

Trigger

and

Holdoff

circuit

initiates

the

action

of

the

Fast

Ramp

circuit.

It

is

coupled

through

Q74

whose

collector

current

switches

D74

from

its

quiescent

high

state

to

its

low

state.

The

resulting

fast

positive

step

turns

@84

off.

Current

from constant-

@i

current

tube

V6]

is

now

diverted

into

the

Ramp

Slope

Ca-

pacitor.

Charging

of

this

capacitor

carries

the

emitter

of

Q93

negative.

The

Staircase

Generator

and

the

DELAY

control

set

the

output

voltage

level

of

the

Slow

Ramp

Inverter,

which,

in

turn,

sets

the

voltage

on the

base

of

Q93.

(Slow

Ramp

is

another

name

for

the

staircase

waveform.)

When

the

fast

ramp

starts,

the

base

of

Q93

is

negative

with

respect

to

its

emitter,

so

Q93

is

not

conducting.

It

remains

cut

off

until

the

fast-ramp

voltage

at

the

emitter

falls

below

the

base

voltage

of

Q93.

Q93

then

turns

on,

passing

current

through

D93

which

is

quiescently

in

its

low

state.

When

this

happens,

D93

switches

to

its

high

state,

developing

a

negative

step.

This

negative

output

is

stepped

up

through

T95

and

is

applied

to

the

base

of

Q94,

The

resulting

positive

step

at

the

collector

of

Q94

is

the

slewed

pulse.

It

is

differentiated

through

C97

and

applied

through

18

of

the

interconnecting

plug

to

the

vertical

plug-in

unit

to

start

the

sampling

process,

and

is

passed

through

R99

to

the

Staircase

Generator

to

advance

the

staircase

one

step.

The

negative

step

at

the

cathode

of

D93

is

also

coupled

back

through

D75

to

switch

D74

to

its

high

state.

This

turns

Q84

on

again,

ends

the

fast

ramp,

and

discharges

the

Ramp

Slope

Capacitor.

With

the

load

impedance

made

up

basically

of

R95

and

the

inductance

of

195,

D93

is

monostable.

Therefore,

it

will

automatically

reset

itself

to

its

low

state

before

the

ramp

is

generated.

The

output

of

the

Staircase

Generator

is

applied

to

the

top

of

R51.

At

this

point,

this

is

about

a

50-volt

positive-

going

staircase

of

100

or

1000

steps.

Thus,

each

step

is

either

0.5

or

0.05

volt

in

amplitude.

Q63

and

Qé64

form

an

inverting

amplifier

with

20k

feedback

resistance.

The

gain

of

this

stage,

from

the

input

of

R53

to

the

output

of

R90,

ranges

from

0.2

to

0.004

depending

upon

the

value

of

R53

selected

by

the

TIME/DIV.

switch.

R54

maintains

a

constant

load

on

R51

and

R52.

The

steps

at

the

Q93

base

are

nega-

tive-going

steps

of

0.1-volt

to

0.2-millivolt

amplitude.

The

smaller

the

steps,

the

less

the

equivalent

time

between

samples,

and

the

faster

the

equivalent

sweep

rate.

The

CALIB.

position

of

R51

(counterclockwise

position

of

the

VARIABLE

control)

is

with

the

wiper

at

the

top

of

R51.

Thus,

as

you

move

the

control

away

from

CALIB.,

you

decrease

the

size

of

the

steps

at

the

base

of

Q93,

decrease

the

equivalent

time

between

samples,

and

consequently

increase

the

equivalent

rate.

The

slope

of

the

fast

ramp

is

changed

between

ranges

by

changing

the

size

of

the

Ramp

Slope

Capacitor.

The

steeper

the

ramp,

the

less

difference

there

will

be

in

the

time

required

for

the

ramp

to

reach

successive

levels

of

the

staircase

at

Q93.

Thus,

the

equivalent

time

per

division

is

controlled

by

varying

both

the

size

of

the

steps

at

the

base

of

Q93

and

the

slope

of

the

fast

ramp

at

the

emitter

of

Q93.

Staircase

Generator

This

circuit

develops

either

a

0.5-volt

per

step

or

0.05-volt

per

step

positive-going

staircase

signal

of

about

50 volts

®

Circuit

Description

—

Type

3177

amplitude

and

applies

it

to

the

Horizontal

Amplifier

and

to

the

Slow

Ramp

Inverter

circuit.

It

also

develops

a

sweep

gate

voltage,

a

positive

gate

lasting

for

the

duration

of

one

complete

staircase

signal.

First,

consider

the

Staircase

Generator

in

its

quiescent

condition,

when

no

staircase

is

being

generated.

Assume

the

SWEEP

MODE

switch

is

in

the

NORMAL

position.

Both

Q135

and

Q145

are

off,

so

Disconnect

Diodes

D152

and

D153

are

conducting

and

the

Miller

Tube

V161

is

on.

D125

is

in

its

low

state.

The

positive

slewed

pulse

fires

the

Miller-Stepping

Block-

ing

Oscillator

Q110.

The

collector

of

Q110

is

held

constant

by

C111

and

C110,

and

the

base

and

emitter

of

Q]110

move

with

current.

The

resulting

negative

swing

at

the

emitter

momentarily

increases

current

through

tunnel

diode

D125

and

switches

it

to

its

high

state.

This

turns

on

Q124,

The

resulting

negative

swing

at

the

collector

of

Q124

passes

through

C127

and

R127

to

the

base

of

Q135.

Q135

turns

on,

and

the

resulting

positive

swing

at

its

collector

turns

Q145

on.

The

negative

swing

at

the

collector

of

Q145

back

biases

the

Disconnect

Diodes

releasing

the

Miller-Capacitor

C160

so

it

can

be

charged.

Conduction

through

Q145

also

holds

Q135

on

through

R140,

so

both

transistors

remain

on

during

the

entire

staircase.

At

the

same

time,

the

negative

gating

voltage

at

the

collector

of

Q145

is

inverted

and

amplified

by

V194A

and

is

applied

to

the

crt

unblanking

deflection

plate

to

unblank

the

crt.

The

negative-going

voltage

step

at

the

Miller-Stepping

Blocking

Oscillator

(emitter

of

Q110}

also

transfers

a

charge

from

Miller-Stepping

Capacitors

C156

or

C158

through

D160

to

C160.

This

raises

the

output

level

of

the

Miller

Integrator

one

step.

The

positive-going

trailing

edge

of

the

Miller-

Stepping

Blocking

Oscillator

then

recharges

the

selected

Miller-Stepping

Capacitor

through

D161

and

C162

in

prep-

aration

for

the

The

size

of

the

charge,

and

therefore

the

size

of

the

steps,

is

determined

by

the size

of

the

Miller-Stepping

Capacitors

and

the

output

voltage

swing

from

the

Miller-Stepping

Blocking

Oscillator.

Each

successive

slewed

pulse

causes

an

identical

charge

to

transfer

from

the

selected

Miller-Stepping

Capacitor

to

C160,

and

thus

raise

the

Miller

Integrator

output

in

identical

increments.

The

output

of

the

Miller

Integrator,

then,

is

a

positive

staircase

that

goes

to

the

Horizontal

Amplifier

and

to

the

Fast

Ramp

Generator.

D177

couples

the

output

voltage

of

the

Miller

Integrator

through

V173A

to

the

top

of

the

V161

plate

load

resistor

R172.

Thus,

as

the

plate

voltage

of

V161

changes,

the

voltage

at

the

top

of

its

plate

load

resistor

(R172)

changes

a

like

amount

and

the

current

through

R172

remains

con-

stant.

The

gain

of

the

Miller

Integrator

approaches

the

amplification

factor

of

V161,

and

the

circuit

operates

with

very

small

changes

in

grid

voltage.

Cathode

follower

V173B

provides

large

output

current

capability.

D178

changes

the

dc

level

of

the

Miller

output

from

+75

volts

to

about

zero

volts.

The

STAIRCASE

DC

LEVEL

adjustment

R181

sets

the

start

of

the

staircase

to

exactly

zero

volts.

When

the

staircase

voltage

reaches

about

+50

volts

it

pulls

the

base

of

Q135

positive

and

turns

off

both

transistors

in

the

Staircase-Gating

Multivibrator.

This

turns

on

the

4-5

Cirevit

Description

—

Type

3177

Disconnect

Diodes

and

discharges

C160

which

resets

the

Miller

Integrator.

D145

disconnects

from

the

staircase

during

reset

while

C145

holds

the

base

of

Q135

positive

for

sufficient

time

to

allow

complete

recovery

of

the

Miller

Integrator.

In

the

SINGLE

DISPLAY

position

of

the

SWEEP

MODE

switch,

the

cathode

of

tunnel

diode

D125

is

connected

through

3.9k

to

—12.2

volts.

This

provides

about

3ma

through

the

tunnel

diode

so

it

may

be

in

either

its

high

state

or

its

low

state.

Assume

that

it

is

in

its

high

state.

This

puts

about

—0.5

volt

at

the

D125

cathode,

and

Q124

will

be

turned

on.

This

draws

the

collector

of

Qi24

to

ground

and

the

negative

blocking

oscillator

pulses

arriving

at

its

emitter

will

have

no

effect.

Thus,

with

D125

in

its

high

state,

the

Staircase

Generator

is

locked

out

and

cannot

be

started.

When

the

reset

button

is

pushed,

current

to

D125

is

momentarily

interrupted

by

the

positive pulse

at

the

top

of

R125,

and

D125

switches

to

its

low

state.

Once

the

reset

pulse

has

passed,

the

current

through

D125

is

again

3

ma,

but

D125

remains

in

its

low

state.

This

cuts

off

Q124,

and

the

from

the

blocking

oscillator

Q110

will

pass

through

Q124

to

start

the

staircase

runup.

The

same

block-

ing

oscillator

pulse

will

also

reset

D125

to

its

high

state

so

the

Staircase

Generator

cannot

be

started

again without

a

reset

pulse.

The

result

is

a

single

staircase.

The

+EXT.

SWEEP

INPUT

and

MANUAL

positions

of

the

SWEEP

MODE

switch

disable

the

Miller-Stepping

Blocking

Oscillator

by

removing

collector

voltage

from

Q110.

They

also

turn

off

Q135

and

Q145,

thereby

turning

on

the

Dis-

connect

Diodes

to

prevent

the

Miller

Integrator

from

running

up.

The

MANUAL

SCAN

control

supplies

voltage

to

RC

filter

R304-C304

(Horizontal

Amplifier

Schematic]

for

smoothing

the

scan.

Horizontal

Amplifier

With

the

SWEEP

MODE

switch

set

to

NORMAL,

the

stair-

case

passes

through

R319

to

the

base

of

Q334.

Q334

and

Q333

form

a

feedback

amplifier

through

R330.

The

output

of

this

amplifier

is

coupled

either

directly,

or

through

a

10X

divider,

to

paraphase

amplifier

V364-V354,

and

then

through

cathode

followers

V373A-V373B

to

the

crt

deflection

plates

via

pins

17

and

21

of

the

interconnecting

plug.

Note

the

leads

at

pins

11

and

12

of

the

interconnecting

plug.

Normally

D327

is

conducting

1

ma

through

R328,

and

12

of

the

interconnecting

plug

is

grounded.

When

the

vertical

plug-in

unit

is

set

for

X-Y

operation

(Vertical

Mode

switch

in

A

VERT.

B.

HORIZ.

on

Type

3576),

11

is

switched

from

—100

volts

through

47k

to

+300

volts

through

47k

(in

the

vertical

plug-in

unit).

This

cuts

off

D327

and

drives

Q334

into

saturation

so

the

staircase

signal

can-

not

get

through.

At

the

same

time,

12

is

switched

from

ground

to

the

output

of

channel

B

in

the

vertical

plug-in

unit.

The

channel

B

signal

is

then

applied

to

the

horizontal

deflection

plates rather

than

the

staircase

waveform.

Mean-

while,

the

channel

A

signal

is

coupled

to

the

vertical

deflection

plates.

This

produces

X-Y

operation.

SECTION

5

MAINTENANCE

PREVENTIVE

MAINTENANCE

Visual

Inspection

The

Type

3177

Plug-In

Unit

should

occasionally

be

inspected

for

such

visual

defects

as

poor

connections,

broken

or

damaged

ceramic

strips,

improperly

seated

tubes

or

transistors,

and

heat-damaged

parts.

The

remedy

for

most

visual

defects

is

obvious;

however,

particular

care

must

be

taken

if

heat-damaged

parts

are

detected.

Overheating

can

be

caused

by

other,

less

apparent

troubles

in

the

circuit.

For

this

reason,

it

is

essential

to

determine

the

actual

cause

of

overheating

before

the

parts

are

replaced;

other-

wise,

the

damage

may

be

repeated.

Recalibration

The

Type

3177

Plug-In

Unit

is

a

stable

instrument

and

will

provide

many

hours

of

trouble-free

operation.

To

main-

tain

the

measurement

accuracy

of

the

Type

3177,

however,

we

suggest

a

check

of

the

calibration

after

each

500

hours

of

operation

{or

every

six

months

if

used

intermittently).

The

calibration

procedure

also

includes

steps

which

will

help

check

for

proper

operation

of

various

circuits.

Minor

troubles

not

apparent

during

regular

operation

will

often

be

revealed

during

calibration.

Also,

major

troubles

in

the

instrument

can

often

be

isolated

or

eliminated

by

calibrating

the

instru-

ment.

Complete

calibration

instructions

are

contained

in

Section

6

of

this

manual.

PARTS

REMOVAL

AND

REPLACEMENT

General

Information

Removal

or

replacement

procedures

for

most

parts

in

the

Type

3177

are

obvious.

However,

some

parts

require

special

procedures.

Removal

and

replacement

of

these

parts

are

discussed

in

the

following

paragraphs.

Many

components

in

the

Type

3177

are

mounted

in

a

particular

way

to

reduce

stray

inductance

and

capacitance.

Therefore,

carefully

instal!

replacement

components

to

dupli-

cate

lead

length,

lead

dress,

and

location

of

the

original

component.

After

replacing

any

electrical

components,

be

sure

to

check

the

calibration

of

the

instrument.

Components

of

the

same

type

usually

exhibit

slightly

different

characteristics

and

will

often

affect

calibration.

Tubes

and

Transistors

Tubes

or

transistors

should

not

be

replaced

unless

they

are

actually

defective.

If

tubes

or

transistors

are

removed

and

found

to

be

acceptable,

be

sure

to

return

them

to

their

original

sockets.

This

will

avoid

recalibration

because

of

different

tube

or

transistor

characteristics.

®

The

best

way

to

check

a

tube

or

transistor

is

by

substi-

tution,

That

is,

replace

the

tube

or

transistor

that

you

wish

to

check

with

a

tube

or

transistor

of

the

same

type

and

of

known

good

quality.

Then,

check

to

see

if

proper

operation

is

restored.

If

not,

return

the

original

tube

or

transistor

to

its

socket.

Wafer

Switches

Individual

wafers

are

normally

mot

replaced

in

the

switch

assemblies

used

in

the

Type

3177.

If

one

wafer

is

defective,

the

entire

switch

assembly

should

be

replaced.

Switches

can

be

ordered

from

Tektronix,

either

wired

or

unwired.

The

wafer

switches

shown

on

the

schematics

are

coded

to

indicate

the

position

of

the

wafer

on

the

switch.

The

wafers

are

numbered

from

front

to

rear

{i.e.,

the

number

1

wafer

is

always

closest

to

the

front

panel].

The

letter

F

and

R

indicate

the

front

or

rear

of

the

wafer.

For

example,

a

code

designation

of

3R

would

mean

the

rear

side

of

the

third

wafer

from

the

front

panel.

Soldering

Precautions

In

the

production

of

Tektronix

instruments,

a

silver-bearing

solder

is

used

to

establish

a

bond

to

the

ceramic

terminal

strips.

This

bond

may

be

broken

be

repeated

use

of

ordinary

tin-lead

solder,

and

by

excessive

heating

of

the

terminal

strip

with

a

soldering

iron.

Occasional

use

of

ordinary

solder

is

permissible

if

applied

with

moderate

heat.

For

general

repair

work,

however,

solder

used

for

the

ceramic

strips

should

contain

about

3%

silver.

If

this

type

of

solder

is

not

available

locally,

it

may

be

purchased

directly

from

Tektronix

in

one-pound

rolls

(part

number

251-514).

A

wedge-shaped

tip

on

the

soldering

iron

is

best

for

soldering

or

unsoldering

parts

on

the

ceramic

strip.

This

type

of

tip

allows

you

to

apply

heat

directly

to

the

solder-

slot

in

the

strip,

reducing

the

overall

heating

effect.

Use

as

little

heat

as

possible

to

establish

a

good

solder

bond.

To

properly

solder

and

unsolder

the

short-lead

compon-

ents,

the

following

procedure

is

recommended.

(1}

Use

long-nose

pliers

for

a

heat

sink.

Attach

the

pliers

between

the

component

and

the

point

where

the

heat

is

applied.

(2)

Use

a

hot

soldering

iron

for

a

short time.

(3)

Carefully

manipulate

the

leads

to

prevent

lead

or

insulation

damage.

(4)

Use

only

a

small

amount

of

solder;

just

enough

to

make

a

good

bond.

Ceramic

Terminal

Strips

To

remove

a

ceramic

terminal

strip,

first

unsolder

all

leads

and

components

connected

to

it.

Then

pry

the

strip,

with

yokes

attached,

out

of

the

chassis.

The

spacers

may

come

out

with

the

yokes.

If

not,

the

spacers

can

be

pulled

out

separately.

However,

if

they

are

not

damaged,

they

may

be

used

with

the

new

stirp

assembly.

5-1

Maintenance

—

Type

3177

Another

way

to

remove

a

strip

from

the

chassis

is

to

use

diagonal

cutters

to

cut

off

one

side

of

each

yoke

holding

the

strip.

This

frees

the

strip

and

the

remainder

of

the

yokes

can

then

be

pulled

free

of

the

chassis

with

a

pair

of

pliers.

Ceramic

strips

are

supplied

with

yokes

at-

tached

so

if is

not

necessary

to

salvage

the

old

yokes.

After

removing

a

damaged

strip

and

yoke

assembly,

place

the

spacers

into

the

holes

in

the

chassis

and

insert

the

yokes

into

the

spacers.

Be

sure

the

yokes

are

completely

seated

in

the

spacers.

If

necessary,

use

a

soft-faced

mallet

to

tap

the

yokes

into

the

spacers.

Fig.

5-1

shows

the

assembled

ceramic

strip.

Fig.

5-1.

Ceramic

strip

assembly.

Test

Points

The

test

points

shown

on

the

schematics

aid

in

trouble-

shooting

and

calibrating

the

Type

3177.

They

simplify

reference

to

particular

locations

in

the

circuitry.

Each

test

point

is

indicated

by

a

bracketed

number

at

its

location

in

the

circuit.

The

fest

points

are

numbered

consecutively

starting

with

the

Trigger

and

Holdoff

circuit.

Physical

location

of

the

test

points

on

the

chassis

of

the

Type

3177

are

shown

in

Figs.

6-2

and

6-3.

TROUBLESHOOTING

General

Information

If

trouble

develops

in

the

sampling

system,

first

check

for

proper

control

settings.

A

control

set

fo

the

wrong

position

can

cause

trouble

symptoms.

Improper

calibra-

tion

can

also

cause

faulty

operation.

By

attempting

to

calibrate

the

instrument,

some

troubles

can

be

isolated

to

a

given

circuit;

if

the

trouble

is

due

to

calibration,

the

trouble

will

be

corrected.

Unusual

troubles

can

be

caused

by

a

failure

in

one

of

the

oscilloscope

power

supplies.

This

should

be

considered

any

time

the

sampling

system

fails

to

operate

properly.

The

oscilloscope

manual

contains

information

for

checking

power

supply

voltages.

If

you

suspect

that

a

tube

or

transistor

in

the

instrument

is

defective,

replace

it

with

a

good

tube

or

transistor

of

the

same

type.

Then

check

to

see

if

the

trouble

symptom

is

eliminated.

If

not,

the

original

tube

or

transistor

is

probably

good

and

should

be

returned

to

its

original

socket.

This

will

avoid

recalibrating

the

instrument

because

of

different

tube

or

transistor

characteristics.

5-2

Tunnel

diodes

can

best

be

checked

by

substitution.

In

some

instances,

however,

a

faulty

tunnel

diode

can

be

detected

with

a

voltmeter.

For

example,

if

the

voltage

across

any

tunnel

diode

in

the

Type

3T77

measures

in

the

range

of

100

to

300

millivolts,

it

is

defective

and

should

be

replaced.

However,

a

tunnel

diode

may

be

faulty

and

not

necessarily

have

a

voltage

in

the

defective

range.

Fig.

5-2

demonstrates

the

polarity

of

the

strip-line

tunnel

diodes

used

in

the

Type

3777.

ar

Anode

Cathode

Fig.

5-2.

Two

views

of

the

strip-line

type

of

tunnel

diode

used

in

the

Type

3177.

TROUBLESHOOTING

PROCEDURE

The

following

troubleshooting

procedure

covers

‘Plug-in

Unit

Isolation”

and

“Circuit Isolation’.

The

first

portion

(Plug-In

Unit

Isolation)

will

help

you

determine

which

plug-

in

unit

is

faulty,

since

a@

failure

in

either

plug-in

unit

can

cause

complete

loss

of

the

display.

The

second

portion

{Table

5-3)

covers

circuit

isolation

for

the

Type

3177.

This

table

will

help

you

locate

a

faulty

circuit

within

the

Type

3777.

Equipment

Required

The

following

equipment

is

recommended

for

trouble-

shooting

the

Type

3177:

1.

Test

oscilloscope,

having

the

following

minimum

speci-

fications:

Deflection

Factor

(not

considering

probe

attenuation)

0.05

v/cm

Bandpass

de

to

10

megacycles

Sweep

Rate

(fastest)

5

psec/cm

2.

De

volt-ohmmeter,

20,000

ohms/volt

sensitivity.

3.

Plug-In

Extension,

Tektronix

part

number

012-066.

4,

Tektronix

Type

109,

110,

or

111

Fast-rise

Pulse

Gen-

erator.

(A

509

10XT

attenuator

is

required

for

use

with

the

Type

111.)

iW

Preliminary

Setup

Before

proceeding

with

the

troubleshooting

procedure,

perform

the

following

steps:

1.

With

the

Type

3177

removed

from

the

oscilloscope,

check

the

resistance

to

ground

at

both

rear

interconnecting

plugs.

See

Tables

5-1

and

5-2

for

typical

resistance

read-

ings.

The

readings

in

the

tables

are

not

absolute

and

may

vary

between

instruments

and

with

different

ohmmeters

and

ohmmeter

scales.

2.

Insert

the

Type

3177

into

the

right-hand

plug-in

com-

partment

of

the

oscilloscope

and

the

vertical

sampling

plug-

in

unit

into

the

left-hand

compartment.

3.

Preset

the

front-panel

controls

of

the

Type

3177

as

follows:

POSITION

Centered

TIME/DIV.

«1

wSEC

HORIZ.

MAG.

X]

DOTS

PER

DIV.

|

100

SWEEP

MODE

NORMAL

INT.-EXT,

INT.

+

Other

controls

may

be

set

to

any

position.

Leave

the

controls

of

the

Type

3177

at

these

settings

{unless

otherwise

noted}

throughout

this

section

of

the

manual.

4.

Apply

a

+

signal

from

the

fast-rise

pulse

generator

to

the

Input

connector

of

the

vertical

plug-in

unit.

(For

the

Type

3876,

apply

a

+

signal

to

the

INPUT

A

con-

nector

and

set

the

INTERNAL

TRIGGER

switch

to

A.)

Turn

on

the

oscilloscope

power

and

allow

about

2

minutes

for

warmup.

“yh

TABLE

5-1

Typical

Resistance

To

Chassis,

P21

Number

Resistance

Number

Resistance

]

20k

13

20

k

2

20k

14

8-10k

3

0

15

8-10k

4 0

|

16

lo

5

|

infinite

17

150k

6

20

k

18

infinite

7

infinite

19

0

8

infinite

20

8-10k

9 0

21

150

k

10

17k

22

0

1

*50

k

&

100k

23

2.3

k

12

3k

24

infinite

*Reverse

ohmmeter

leads

to

get

both

resistance

values.

®

Maintenance

—

Type

3177

TABLE

5-2

Typical

Resistance

To

Chassis,

P22

Number

Resistance

Number

Resistance

1

infinite

13

6.4k

2

infinite

14

infinite

3

infinite

15

infinite

4

infinite

16

infinite

5

infinite

17

infinite

é

infinite

18

infinite

7

infinite

19

infinite

8

infinite

20

1k

9

infinite

21

2k

10

infinite

22

infinite

1

|

infinite

23

infinite

12

|

__

infinite

24

infinite

Plug-In

Unit

Isolation

If

trouble

in

the

sampling

system

makes

it

impossible

to

obtain

a

display

on

the

crt,

the

following

steps

will

help

you

determine

which

plug-in

unit

is

faulty.

1.

Turn

the

Type

3177

TRIGGER

SENSITIVITY

control

fully

clockwise

and

{with

the

test

oscilloscope)

check

the

signal

at

test

point

[8]

in

the

Type

3177.

The

waveform

on

the

test

oscilloscope

should

resemble

that

shown

on

the

schematic

(Staircase

Generator).

If

there

is

no

wave-

form

at

test

point

[8],

the

Type

3177

is

faulty.

2.

With

the

test

oscilloscope,

check

the

signals

at

test

points

[23]

and

[24].

The

waveforms

should

resemble

those

shown

on

the

Horizontal

Amplifier

schematic.

If

the

waveforms

are

not

proper,

the

trouble

is

in

the

Type

3177.

If

the

waveforms

at

test

points

[23]

and

[24]

are

proper,

the

trouble

is

in

the

vertical

sampling

plug-in

unit.

3.

Apply

a

signal

to

the

Input

connector

of

the

vertical

sampling

plug-in

unit.

Set

the

necessary

controls

to

trigger

the

Type

3177

from

the

applied

signal.

4.

Connect

the

input

of

the

test

oscilloscope

to

the

Type

3177

TRIG.

OUT.

connector.

Starting

from

the

ex-

treme

counterclockwise

position,

slowly

turn

the

Type

3177

TRIGGER

SENSITIVITY

control

until

a

waveform

first

ap-

pears

at

the

TRIG.

OUT.

connector.

5.

Remove

the

signal

from

the

input

of

the

vertical

unit;

the

signal

at

the

TRIG.

OUT.

connector

should

dis-

appear.

If

not,

the

internal

triggering

signal

is

not

trig-

gering

the

Type

3177.

The

fault

is

either

in

the

trigger

take-

off

circuitry

of

the

vertical

plug-in

unit, or

in

the

coupling

between

the

trigger

takeoff

circuitry

and

the

Type

3177.

If

the

signal

at

the

TRIG.

OUT.

connector

is

present

regard-

less

of

the

setting

of

the

TRIGGER

SENSITIVITY

control,

the

trouble

is

in

the

Type

3177.

5-3

Tektronix 3177 User manual

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