Tektronix 7b51 User manual

L

C·

L

INSTRUCTION

MANUAL

Tektronix,

Inc

.

TYPE

7851

DEI.AYING

TIME-BASE

S,W.

Millikan

Way

. P. O. Box

500

• BeaYerton,

Oregon

97005

• Phone

644

-0161 • Cables: Tektronix

070

.

097

6.00

869

Scans

By

Arlel.Media

Artek Media

1042

P

lu

mme

r

Cir

. SW

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MN

55902

www.artekmedia.com

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WARRANTY

All

Tektronix ,instruments

are

warranted

against

defective materials

and

workman-

ship for

(>ne

year. Tektronix transformers,

manufactured

in

our

plant,

are

warranted

for the life of

the

instrument.

Any questions with respect to 'the war-

ranty mentioned Qbove should

be

taken

up

with

your

Tektronix Field Engineer.

Tektro,"ix repa,ir

and

repla<;~m1/lnt.Pdrt

servke

is

geared

directly to.;

th~fj~ld,

th~refore

all requests for repoirs

ond

re-

placement

parts$hould

be

directed

to

the

Tektronix Field Office

or

representative

in

your

area.

This

procedure will assure

you the fastest possible service. Please

include

the

instrument Type

and

Serial or

Model Number with all requests for parts

or

service.

Specifications

and

price

change

privi-

leges reserved.

1969

by Tektronix, Inc.,

Beaverton,

Oregon.

Printed

in

the

United

States of America.

All

rights reserved.

Contents

of

this publication

may

not

be

reproduced

in

ony

form without permis-

sion

of

the

copyright

owner.

®

TABLE

OF

CONTENTS

SECTION 1

SECTION 2

SPECIFICATION

Introduction

Electrical Characteristics

Sweep Rate

Sweep Accuracy

Sweep

length

Sweep Hold-Off Time

Delay Time Multiplier

Range

Accuracy

linearity

Delay

Jitter

Trigger Sensitivity

Internal Trigger

Jitter

External Trigger Input

level Range

Bright Baseline

POp

Auto Sensitivity

Environmental Characteristics

Altitude

Transportation

Physical Characteristics

Finish

Weight

Dimensions

OPERATING INSTRUCTIONS

General

Installation

Front

Panel Controls and Connectors

Test Setup Chart

General Operating Information

Sweep Calibration Check

Simplified Operating Instructions

Normal Sweep

Magnified Sweep

Delayed Sweep

Pushbutton Switch

logic

Triggered

light

Trigger Mode

Trigger Coupling

Trigger Source

Trigger Slope

Trigger level

Horizontal Sweep Rate

Sweep Magnifier

Horizontal Position Control

Applications

Measurement Techniques

Time Duration Measurements

Page

1-1

1-2

2-1

2-4

2-6

2-7

2-9

2-10

2-12

2-13

2-14

Type 7B51

SECTION 3

SECTION 4

ii

TABLE

OF

CONTENTS

Determining Frequency

Risetime Measurements

Delayed Sweep Time Measurements

Delayed Sweep Magnification

Pulse

Jitter

Measurements

CIRCUIT DESCRIPTION

Introduction

Block Diagram Description

Detailed Circuit Description

Trigger Preamp and Input Switching

Trigger Generator

Input Stage

P-P

Auto Stage

Slope Comparator

Trigger TO Stage

Pulse Amplifier

Sweep Gate Stage

Bright Line Auto

Sweep Generator

Disconnect Amplifier

Sawtooth Generator

Sweep

Start

Amplifier

Sweep

Stop

Comparator

Holdoff Capacitor and Amplifier

Sweep Holdoff Multivibrator

Reset Control Amplifier

Sweep Reset Multivibrator

Single Sweep Operation

Alternate Operation

Delayed Sweep Operation

Delay Pickoff Circuit

Horizontal Preamp

Readout Block

MAINTENANCE

Preventive Maintenance

General

Cleaning

Transistor Checks

Recalibration

Troubleshooting

Troubleshooting Aids

Troubleshooting Equipment

Troubleshooting Techniques

Corrective Maintenance

Obtaining Replacement Parts

Soldering Techniques

Component Replacement

cont

2-14

2-15

2-16

2-17

2-18

3-1

3-3

3-6

3-7

3-9

3-10

3-11

3-12

4-1

4-2

4-~

4-2

4-6

4-7

®

SECTION 5

SECTION 6

SECTION 7

SECTION 8

TABLE

OF

CONTENTS

PERFORMANCE CHECK/CALIBRATION

Introduction

Test Equipment Required

Short

Form Procedure

Performance Check/Calibration Procedure

General

Preliminary Control Settings

Check

or

Adjust

Level

Center

P-P

Auto

Level

Range

Internal Trigger Centering

Level/Slope Range

Trigger Bandwidth

External Trigger Input Compensation

Sweep

Jitter

Trigger Modes

Sweep Calibration

Magnified Sweep Gain

Magnifier Registration

Sweep Length

Variable Time/Div Range

5fJ.s Timing

0.2

fJ.s

Timing

Sweep Timing Accuracy

Magnified Sweep Timing

Sweep Inhibit

Delay

Start

(R590) and Delay

Stop

(R500)

Delay Time Accuracy

Delay Time

Jitter

Line Trigger Source

ELECTRICAL PARTS LIST

Abbreviations and Symbols

Parts Ordering Information

Index

of

Electrical Parts List

cont

DIAGRAMS AND MECHANICAL PARTS ILLUSTRATIONS

Diagrams

Mechanical Parts Illustrations (on reverse side

of

Diagrams)

MECHANICAL PARTS LIST

Mechanical Parts List Information

Index

of

Mechanical Parts Illustrations

Mechanical Parts List

Accessories

5-1

5-2

5-4

5-5

5-6

5-7

5-8

5-9

5-10

5-11

5-.12

5-13

5-14

Abbreviations and symbols used

in

this manual are based on

or

taken directly from IEEE

Standard

260

"Standard

Symbols for Units",

MIL

STD-12B and

other

standards

of

the

electronics industry. Change information, if any,

is

located

at

the rear

of

this manual.

-----~------------~-----~----

Type 7B51

iii

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-

Type 7851

<ill

Type

7B51

SECTION

1

SPECIFICA

TION

Change

information,

if

any,

affecting

this section

will

be

found

at

the rear

of

the manual.

Introduction

The

Type

7B51 Time Base Unit

is

designed specifically

for use with

Tektronix

Type

7500-Series Oscilloscopes.

However, it

is

compatible

with all 7000-Series Oscillo-

scopes. The

Type

7B51 provides calibrated sweeps from 5

seconds/division

to

0.05

microsecond/divisions (5 nano-

seconds/division

with

X10

MAGNIFIER). Sweep rates

may

be varied

continuously

(uncalibratedl between calibrated

steps. Sweep triggering

is

to

100

megahertz

or

vertical

amplifier

bandwidth,

whichever

is

less. The delaying sweep

feature of

the

Type

7B51,

in

delayed sweep

operation,

gives

continuous

sweep delay from 0

to

10

times

the

setting

of

the

TIME/DIV OR

DL

Y TIME selector. The sweep free-

runs, providing a bright base line

in

the

absence

of

adequate

triggering signal

in

P-P

AUTO and AUTO triggering modes.

The Performance Check procedure given

in

Section 5

provides a

convenient

method

of

checking performance

of

this instrument.

The

following electrical characteristics

apply

at

an

ambient

temperature

of

O°C

to

+50°C, unless

otherwise

noted.

Warmup time for given accuracy

is

20

minutes.

TABLE

1-1

ELECTRICAL CHARACTERISTICS

Characteristic Performance Characteristic Performance

-- _

...

Sweep Rate Over any 2 div

5%

7%

Calibrated Range 5 seconds/division

to

0.05

micro- interval within

second/division in a 1-2-5 sequence.

center

8 div

X

10

magnifier

extends

sweep rate

to

5 nanoseconds/division. Exclude following

Start

of

Sweep End

of

Sweep

portions

of

Magni- first

50

ns

beyond

the

VARIABLE

Continuously

variable between cali- fied Sweep

100th

div

Range (uncali-

brated

sweep rates.

Extends

uncali-

bratedl bra

ted

sweep rate

to

at

least 12.5 Sweep Length 10 divisions

to

13 divisions

seconds/division. Sweep Hold-Off

Time

5 s/Div

to

1.5 times

the

TIME/DIV setting

or

Sweep Accuracy Measured

in

7500

series mainframe 5

]..ls/Div

less.

Calibrated

with

mainframe calibra- 2

]..ls/Div

to

3.5

microseconds

or

less.

tor.

0.05

]..ls/Div

+15°C

to

+35°C

O°C

to

+50

oC

Time Interval DELAY TIME o

to

10

times TIME/DIV setting

Over Center Unmag

Mag

Unmag

Mag

8 div

MULTIPLIER

Range

5 s/div

to

0.1 3% 3.5%

4%

5% Accuracy

s/div and

0.2

5 seconds/division Within

2%

]..ls/div

to

0.05

to

1 second/divi-

]..ls/div

sion

.5 milliseconds/ Within

1%

50

ms/div

to

2%

2.5% 3%

4%

division

to

1 micro-

0.5

]..ls/div

second/division

,-,

Specification-

Type

7B51

Characteristic Performance

Multiplier Accuracy Within 0.2%

Differential

Time

Within

1%

and 2

minor

divisions

for

Measurement delay times 1 llS

to

0.5

s

Accuracy Within

2%

and 2

minor

divisions

for

delay times 1 s

to

5 s

Jitter

1

part

or

less in

50,000,

of

10

times

the

TIME/DIV setting

Trigger Sensitivity Minimum

Triggering Triggering

Frequency

Signal

Rangel Required

Coupling INT EXT

--

AC

30

Hz-10

MHz

0.3

Div

150

mV

10

MHz-100

MHz

1.5 Div

750mV

AC

LF REJ2

30

kHz-10

MHz

0.3

Div

150

mV

10

MHz-100

MHz

1.5Div

750mV

AC HF

REJ

30

Hz-50

kHz

0.3

Div

150

mV

DC

DC-10

MHz

0.3Div

150

mV

10MHz-100M!:Iz

1.5Div

750mV

Single Sweep Triggering

requirements

same as

normal sweep. When triggered,

sweep generator

produces

one

sweep

only.

Internal Trigger 1 nanosecond

or

less

at

75

mega·

Jitter

hertz.

External Trigger

Input

Maximum

Input

500

volts (DC + Peak AC).

500

Voltage volts (p.p AC)

at

1 kilohertz

or

less.

Input

Rand

C 1 megohm within 2%;

20

picofarads

within 2 picofarads.

10n

Internal

Triggering

Only.

the

specification

for

-3

dB

frequency

of

the

Vertical

System

replaces

any

frequency

in

the

above

table

when

the

number

in

the

table

is

greater

than

the

-3

dB

frequency

of

the

Vertical Amplifier.

2WiII

not

trigger

on

sine waves

of

3 divisions

or

less internal

or

1.5

volts

external

below

120

Hertz.

1·2

Characteristic

Level Range (Ex·

cluding

p.p

AUTO)

EXT

EXT +

10

Bright Baseline

p.p AUTO Opera·

tion

Sensitivity

Performance

At

least +3.5 volts

to

-3.5

volts.

At

least

+35

volts

to

-35

volts.

Sweep free·runs in absence

of

triggering signal in

p.p

AUTO

and

AUTO.

0.5

div Internal,

250

millivolts

External.

TABLE

1·2

ENVIRONMENTAL CHARACTERISTICS

This

instrument

will meet

the

electrical characteristics given

in

Table

1·1

over

the

following environmental limits.

Characteristic

Altitude

Non·operating

Transportation

Performance

To

50,000

feet and

-55°C.

Qualified

under

National Safe

Tran·

sit

Committee

test

procedure

1A,

category II.

TABLE

1·3

PHYSICAL CHARACTERISTICS

Finish

Dimensions

Weight

Front

panel

is

anodized aluminum.

14

1/4

inches long by 2

5/8

inches

wide by 5 inches high.

Approximately

1 3/4 pounds.

®I

TYPE 7B51

SECTION

2

OPERA

TING

INSTRUCTIONS

Change

information,

if

any,

affecting

this section

will

be

found

at

the rear

of

the manual.

General

The Type 7B51 delaying sweep plug-in unit operates

with a Tektronix 7000-series indicator oscilloscope and a

7A-series vertical plug-in

unit

to

form a complete oscillo-

scope system. To use

the

Type

7B51 effectively,. its

op~ra

tion and capabilities should be known. ThiS section

describes

the

operation

of

the

front-panel controls, gives

first-time and general operating information and lists some

basic applications for

this

instrument.

Installation

The Type 7B51

is

designed

to

operate

in

the

horizontal

plug-in

compartments

of

Tektronix 7000-series oscillo-

scopes. The Type 7B51 can also be installed

in

a vertical

plug-in

compartment

to

provide a sweep

that

runs vertically

on

the

CRT. However, when used

in

this manner, there is

no retrace blanking

or

internal triggering provision and

the

unit may not meet

the

specifications given

in

Section 1.

The instructions

in

this manual are written

for

use

of

the

Type 7B51

in

a horizontal plug-in

compartment

of

the

oscilloscope.

When

the

Type 7B51

is

used with an oscilloscope which

has

two

horizontal plug-in compartments, install this unit

in

the A (DELAYING TIME BASE)

compartment.

Then,

if

a

delayed-sweep unit

is

installed

in

the

B (right) compart-

ment, delayed-sweep operation

is

available. The

Type

7B51

will operate properly

in

the

B

compartment

for all horizon-

tal modes

of

operation

except

delaying sweep.

To install

the

Type

7B51 into a plug-in

compartment,

push it

in

until it fits firmly into

the

indicator plug-in

compartment. To remove, pull

the

release latch (see Fig.

2-1)

to

disengage

the

unit

from

the

indicator and pull it

out

of

the

plug-in

compartment.

Even though

the

horizontal

gain

of

the

indicator oscilloscope

is

standardized

to

minimize adjustment when inserting plug-in units,

the

sweep calibration of

the

Type 7B51 should be checked

when it

is

inserted into

the

indicator

to

verify measurement

accuracy. The procedure for checking

the

unit

is

given

under Sweep Calibration Check

in

this section.

FRONT~ANELCONTROLSANDCONNECTORS

General

All

controls required for

the

operation

of

the

Type 7851

are located

on

the

front

panel

of

the

unit

(see Fig. 2-2).

To

make full use

of

the

capabilities

of

this instrument,

the

II

B

TflIGGERABl£

AfffR

IJ£IAY

DELAY

TIME

MUlT

TfkTRONI)(®

7851

Fig. 2-1.

Location

of

release

latch.

operator should be familiar with

the

function and use of

each of these controls. A brief description

of

the

front-

panel controls and connector

is

given here. More detailed

information

is

given under General Operating Information.

Triggering Controls

LEVEL/SLOPE

TRIG'D

Selects

the

amplitude

point

and

slope

of

trigger signal

on

which

the

sweep

is

triggered. When

the

indica-

tor

line on

the

outer

ring

is

to

the

left

of

center,

the

sweep

is

triggered

on

the

positive-going slope

of

the

trigger signal, as shown by

the

positive-going waveform. To

the

right of center,

the

sweep

is

trig-

gered on

the

negative-going slope

of

the

trigger signal as shown by

the

negative-going waveform.

Light indicates

that

the

sweep

is

triggered and will produce a display

with correct setting

of

the

POSI-

TION control and

the

controls

on

the

associated vertical unit and indi-

cator oscilloscope.

2-1

Operating Instructions-Type 7851

OELAY

CONTROLS

t1116

'D .

LEvtL

/SLOPE

.

.......

........

•

1'

III

.(

.........

TRIGGERING

....

CDUI'UlI6

SO"'"

......

~

,~

• • •

.

,"

~

....

..

,

• • •

AeMfRU m

• •

Fig, 2,2,

Fron

t·

P

ene

l

con

trols and

connector

.

MODE

2-2

Series of push·button switches to

se

lect the t

rigg

er mode. Selected

mod

e is

indicated

by

li

ghted

button.

p.p AUTO: Sweep automatica

ll

y

triggered at point

se

lected

by

the

LE V

EL

IS

LOPE

control when

the trigger s

ign

al

repetition rate

is

above abo

ut

200 hertz and

with

in

the

frequency range

sel

ecte

d by

the

COUPLING

TRIGGER

CONTROLS

SWEEP

CONTROLS

TRIGGER

CONTROL

switch. Tri

gge

red sweep can be

obta

in

ed throughout the range

of the

LE

VE

LIS

LOPE

contro

l.

When the t

ri

gger repetition rate

is

below the lower frequency

limit

(o

r above upper limit for

AC

HF

REJ)or when the trigger

signal is inadequate, the sweep

free runs

at

the sweep rate

se

l

ected

by

the

TI

ME/DIV

switch

to

produce a reference

trace.

®I

AUTO:

Sweep initiated

by

the

applied trigger signal

at

point

selected by

the

LEVEL/SLOPE

control when

the

trigger signal

repetition rate

is

above

about

30

hertz and within

the

frequency

range

selected

by

the

COU-

PLING switch. Triggered sweep

can be obtained only over

the

amplitude range

of

the

applied

trigger signal. When

the

LEVEL!

SLOPE control

is

outside

the

amp

lit

ude range,

the

trigger

repetition

rate

is

below

the

lower frequency limit (or above

upper limit for

AC

HF REJ)

or

the

trigger signal

is

inadequate,

the

sweep free runs

at

the

sweep

rate selected

by

the

TIME!DIV

switch

to

produce a reference

trace.

NORM: Sweep initiated

by

the

applied

trigger signal

at

any

point

selected by

the

LEVEL!

SLOPE control over

the

fre-

quency range selected by

the

COUPLING switch. Triggered

sweep can be obtained only over

the

amplitude

range

of

the

applied trigger signal. When

the

LEVEL/SLOPE control

is

out-

side

the

amplitude range,

the

trigger repetition rate

is

outside

the

frequency range selected

by

the

COUPLING switch

or

the

trigger signal

is

inadequate, there

is

no trace.

SINGLE SWP: Sweep initiated

by

the

applied trigger signal

at

any

point

selected by

the

LEVEL/

SLOPE control over

the

fre-

quency range selected by

the

COUPLING switch. Trigger-'!d

sweep can be obtained only over

the

amplitude range. of applied

trigger signal. After

the

first

sweep

is

displayed,

further

sweeps

cannot

be presented until

the

RESET-READY

push-

button

is

pressed. When

the

LEVEL/SLOPE control

is

out-

side

the

amplitude range,

the

trigger repetition rate

is

outsidtl

the

frequency range selected by

the

COUPLING switch,

the

trig-

ger signal

is

inadequate

or

when

the

RESET-READY light

is

off,

there

is

no trace.

COUPLING

SOURCE

Operating

Instructions-Type

7851

RESET-READY: Push-button

to

reset

the

Sweep Generator for

the

next sweep

in

the

single-

sweep

mode.

The

RESET-

READY

button

remains lighted

to

indicate

that

the

unit

is

ready

to

be triggered. After

the

unit

is

triggered and a sweep

is

com-

pleted,

the

RESET-READY light

goes

out

until

the

button

is

pressed again.

Series

of

push-button switches

to

select

the

trigger coupling. Selected

coupling

is

indicated by lighted

button.

AC:

Rejects

DC

and attenuates

AC

signals below

about

30

hertz.

Accepts signals between

30

hertz

and 100 megahertz.

AC LF R

EJ:

Rejects

DC

and

attenuates signals below

about

30

kilohertz. Accepts signals

between

30

kilohertz and 100

megahertz.

AC

HF REJ: Accepts signals be-

tween

about

30

hertz and

50

kilohertz. Rejects

DC

and atten-

uates signals outside this fre-

quency range.

DC: Accepts all trigger signals from

DC

to

100 megahertz.

Series of push-button switches

to

select

the

trigger source. Selected

sou

rce

is

indicated by lighted

button.

INT: Trigger signal obtained inter-

nally from a vertical unit.

LI

NE:

Trigger

signal obtained

internally from a sample

of

the

line

voltage

applied

to

this

instrument.

EXT: Trigger signal obtained from

an external signal applied

to

the

EXT TRIG

IN

connector.

EXT + 10: Trigger signal obtained

from an external signal applied

to

the

EXT TRIG

IN

connector

as

in

the

EXT position.

In

this

position

the

external signal

is

attenuated

10 times before it

is

applied

to

the

trigger circuit.

2-3

---

--

------------

Operating

Instructions-Type

7B51

EXT TRIG

IN

Sweep Controls

POSITION

FINE

TIME/DIV OR

DLY

TIME

VARIABLE

MAGNIFIED

SWPCAL

2-4

Input

connector

for external trigger

signal.

Controls horizontal position

of

dis-

play.

Provides more precise control

of

horizontal position.

Selects

the

basic sweep rate

of

the

output

sawtooth and selects basic

delay time (to be multiplied by

the

DELAY TIME MULT dial setting).

The VARIABLE control

must

be

in

calibrated

position

and

MAG-

NIFIED switch

set

to

Xl

for

indi-

cated sweep rate.

Two-position switch actuated by

the

VARIABLE knob

to

select cali-

brated

or

uncalibrated sweep rates.

At

the

in

position,

the

VAR IABLE

control

is

inoperative and

the

sweep

rate

is

calibrated. When pressed and

released,

the

knob moves

out

to

activate

the

VAR IABLE control

for

uncalibrated

sweep rates. The

sweep

rate

in

each TIME/DIV

switch position can be reduced

to

at

least

the

sweep rate

of

the

to

provide con-

tinuously variable sweep rates from

5

nanoseconds/division

(Xl0·

MAGNIFIER on)

to

about

12.5

seconds/division,

with MAGNI-

FIER

at

X1.

Push-button switches

to

select

the

horizontal

magnification.

The

Selected magnification

is

indicated

by a lighted

button.

Xl

:Magnified sweep

at

the

basic

sweep rate indicated by TIME/

DIV switch.

Xl0:

Magnified sweep

at

a sweep

rate

10

times faster

than

the

basic sweep rate indicated by

the

TIME/DIV switch. The portion

of

the

normal sweep within

the

center

division

of

the

graticule

is

the

portion shown

in

magnified

form.

Screwdriver

adjustment

to

set

amplitude

of

the

output

sawtooth.

Delay Controls

B DELAY MODE

(A

INTEN

DURING

B)

Series

of

push-button switches

to

select

the

delay logic

to

the

com-

panion

delayed-sweep

unit

(B).

Selected delay mode

is

indicated by

a lighted

button.

INDEPENDENT: The Type 7B51

and

the

companion delayed-

sweep unit

(B)

operate inde-

pendently as normal time-base

units.

B STARTS AFTER DELAY: The

companion delayed-sweep unit

(B)

produces a sweep immediate-

ly

following

the

delay time selec-

ted

by

the

TIME/DIV

OR

DL

Y

TIME switch and

the

DELAY

TIME MULT dial.

B

TRIGGERABLE

AFTER

DELAY: The companion delayed-

sweep

unit

(B)

produces a sweep

after

the

first trigger pulse

is

received

following

the

delay

time

selected by

the

TIME/DIV

OR

DL

Y TIME switch and

the

DELAY TIME

MUL

T DIAL.

DELAY TIME

MUL

T

Provides

variable delay for

the

delay

pulse

to

the

companion

delayed-sweep unit

(B)

from 0

to

10

times

the

basic delay time selec-

ted

by

the

TIME/DIV OR DELAY

TIME switch.

TEST SETUP

CHART

General

Fig. 2-3 shows

the

front

panel

of

the

Type 7B51. This

chart

can be reproduced and used as a test-setup record for

special measurements, applications

or

procedures,

or

it

may

be used as a training aid for familiarization with this instru-

ment.

GENERAL

OPERATING

INFORMATION

Sweep Calibration Check

Whenever

the

Type

7B51

is

inserted into a plug-in com-

partment

other

than

the

one

in

which it was calibrated, the

sweep calibration shoUld be checked and readjusted if

necessary. Allow five minutes warmup before performing

this procedure.

1. Connect a one-kilohertz calibrator signal from

the

Indicator Oscilloscope Calibrator

to

the

Vertical unit input

connector.

®

Operating

Instructions-Type

7851

TYPE

7851

TEST

SET

-UP

CHART

TRIS'D

0 TRIGGERING

MODE

COUP1J18

SOURCE

LEVEl/SLOPE p.p

AUI'O

AC

lIlT

f@ 0 0 0

AUTO

AC

LFREJ

UIE

0 D D

IORM

AC

"FlU

EXT

D D 0

;]

DC

00+.

D D

FINE

POSITION

RESET

0 MAGNIFIER

0

READY

o

XI

o

XID

8 DELAY MODE

(A

IITEI

DURI".I

D

IIII£PElDEIT

0 •

STAII11

AFTER

D£l.AY

D • Tlll88£RAIU

AFTER

DElAY·

DELAY

TIME

MULT

@

EXT

TRIG

IN

SWP

e

CAL

e

TEKTRONIX®

7851

DELAYING TIME BASE

NOTES:

Fig.

2·3.

Type

7851

Test

Setup

Chart.

2-5

Operating

Instructions-Type

7851

2. Set

the

TIME/DIV switch

to

1 ms and press

the

top

TRIGGERING and B DELAY

MODE

pushbuttons.

3. Set the Vertical

unit

to

display

at

least two divi-

sions of

the

signal vertically.

4. Check

the

CRT display for one complete cycle per

division.

5.

If

necessary, adjust

the

SWP

CAL adjustment for one

complete cycle per division.

Simplified Operating Instructions

The following information

is

provided

to

aid

in

quickly

obtaining

the

correct settings for

the

Type 7B51

to

present

a display. The operator should be familiar with

the

com·

plete function and operation

of

the

unit as described

in

this

section before using this procedure.

Normal Sweep. The following procedure will provide a

stable display for most normal·sweep applications.

1. Select

the

TRIGGERING MODE, COUPLING and

SOU

RCE

which

fit

the

requirements

of

the

signal

to

be

displayed.

2. Turn

the

LEVEL/SLOPE control

to

the

desired

slope.

3.

If

the

green TRIG'D light

is

not

on,

adjust

the

LEVEL/SLOPE control throughout

the

range

of

the

selec-

ted slope until

the

TRIG'D light comes

on.

If

the

light does

not

come on

at

any setting

of

the

LEVEL/SLOPE control,

the trigger signal

is

inadequate

or

the

COUPLING and

SOURCE switches are set incorrectly.

4.

Set

the

TIME/DIV switch and POSITION control for

a display which remains

on

the

display area horizontally

(VARIABLE control should be

in

CAL position for cali·

brated sweep rates).

5.

If

the

display does

not

start

at

the

correct

point

on

the

waveform, readjust

the

LEVEL/SLOPE control for

the

desired triggering.

Magnified Sweep. A magnified·sweep display can be

obtained as follows after a normal-sweep display

is

obtained

as given

in

steps 1·5 above.

1. Adjust

the

POSITION control

to

move

the

area

to

be

magnified within

the

center division

of

the

CRT.

2·6

2.

If

necessary, change

the

TIME/DIV switch setting so

the complete area

to

be magnified

is

within the center divi·

sion.

3. Press

the

X10·MAGNI FlED push·button.

4. Use the fine range

of

the

POSITION control

to

establish precise positioning

of

the

magnified display.

Delayed Sweep. The following procedure can be used

to

obtain a delayed·sweep display when

the

Type 7B51

is

used

in

an oscilloscope

that

has dual time base capabilities and

when used with a companion delayed·sweep unit (B).

Obtain a display as given

in

steps 1·5 under Normal Sweep.

Then proceed as follows:

1. Press

the

B STARTS AFTER DELAY push-button.

2. Set

the

indicator oscilloscope horizontal mode

to

dis-

play

the

A time base (Type 7B51).

3.

Set

the

time/division switch

of

the

companion

delayed-sweep unit

(B)

so

the

intensified zone

on

the

dis-

play

is

the

desired length (intensified zone will be displayed

in

delayed form).

If

the

intensified zone

is

not

visible,

adjust

the

indicator intensity controls.

4. Adjust

the

DELAY TIME

MUL

T dial

to

position

the

intensified zone

to

the

portion of

the

display

to

be delayed.

5.

Set

the

indicator oscilloscope horizontal mode

to

dis·

play

the

B time base (delayed sweep unit).

6.

If

a delayed sweep with less jitter

is

desired, press

the

Type 7B51 B TRIGGERABLE AFTER DELAY push-

button. The triggering controls

of

the

companion delayed-

sweep

unit

(B)

must be set

to

obtain a stable display. See

the instruction manual for

that

unit

for further informa·

tion.

Pushbutton Switch Logic

The TRIGGERING MODE, COUPLING and SOURCE

switches and

the

B DELAY

MODE

switch are arranged

in

a

sequence which places

the

most often-used position

at

the

top

of

each series

of

pushbuttons. With this arrangement, a

stable normal·sweep display can usually be obtained by

pressing

the

top

push·buttons; p.p AUTO, AC, INT and

INDEPENDENT. When an adequate trigger signal

is

applied,

the

unit

is

triggered as indicated by

the

illuminated

TRIG'D light

at

any setting of

the

LEVEL/SLOPE control.

If

the

TRIG'D light

is

not

on,

either

the

trigger signal

applied

to

this unit from the vertical unit is inadequate

or

it

is

below

the

lower frequency limit

of

the

AC

COUPLING

switch position.

If

the

desired display is

not

obtained with

the push

buttons

pushed in,

othe

r selections must be made.

Aefer

to

the following discussions

or

the

instruction

manuals for the associated indicator oscilloscope

and

verti-

cal

unit

for more information.

Triggered Light

The

TAIG'D

light:

provides a convenient indication

of

the

condition

of

the

triggering circuits.

If

the

TAIG-

GERING controls are correctly set

and

an adequate trigger

signal

is

applied,

the

TAIG'D light

is

on.

Under certain

conditions,

the

TRIG'O light may be

off,

indicating

that

the sweep

is

not

triggered.

The

cause might be a mis-

adjusted LEVEL/SLOPE control, incorrectly

set

COU-

PLING

or

SOURCE switches, low trigger signal amplitude,

or

a trigger signal repetiti

on

rate outside

the

acceptable

frequency range. This feature can be used as a general indi-

cation

of

co

rr

ect

triggering. It is particularly useful when

setting up the trigger circuits when a trigger signal is avail·

able

without

a display

on

the CAT. It also indicates

that

this unit

is

correctly triggered when operating as a delaying·

sweep unit (A).

Trigger Mode

The

pushbuttons

located

under

the MODE title (see Fig.

2·4) select

the

mode

in which

the

sweep is triggered. The

selected

mode

is

indicated by a lighted

pushbutton.

MODE

pl.tShbuttOM

--.

l£VEl/SlOH

"'ill

.-os.no..

._-

ts

__

..

.---

COUPLING SOURCE

pusnbullonl

pushbuuoni

T"~I('U"G

/

-

--

...

......

K

..

• • •

-

K.~

..

• • •

-

K.~

..

• • •

~J

..

•

Fig. 2-4.

Exploded

...

tew

of

front

JIIIn,l snowing

push-bultoni

..aei~ed

with

the

MODE,

COUPLING

.nd

SOURCE swileh

...

®i

Operating

Instructions-Type

7851

p.p AUTO. When the p.p AUTO

pushbutton

is pressed,

a triggered display is provided

at

any setting

of

the

LEVEL/

SLOPE control whenever an adequate trigger signal

is

applied.

The

range

of

the LEVEL/SLOPE control

in

this

mode

is between

about

10% and 90%

of

the

peak·

to

·peak

amplitude

of

the

applied trigger signal. The LEVELISLOPE

control can be

set

so

the

displayed waveform starts

at

any

point within this range

on

either sl

ope.

In

the

p.p

AUTO

mode, the trigger circuit automatically compensates for

changes

in

trigger signal amplitude for signals above

the

minimum

amplitude

requirement. Therefore, if

the

LEVEL/SLOPE control is set so

the

displayed waveform

starts

at

8 certain percentage-point

on

the

leading edge

of

a

low

-a

mplitude signal, it triggers

at

the same percentage·

point

on

the

leading edge of a high-amplitude signal if the

LEVEUSLOPE control is

not

changed. This operation is

illustrated in

Fig

. 2·5.

When

the

trigger repetition

rate

is below

about

200

hertz

(or outside the frequency range selected by

the

COUPLING

switch),

or

when

the

trigger signal

is

inadequate,

the

sweep

free runs

at

the

sweep rate indicated by

the

TIME/DIV

switch

to

produce a reference trace (TRIG'O light off).

When an adequate trigger signal is again applied,

the

free-

running condition ends

and

a triggered display is presented.

The

p

.p

AUTO trigger mode

is

particularly useful when

observing a series

of

waveforms, since it

is

not

necessary

to

reset

the

LEVEL/SLOPE

contro

l for each observation.

Also, because

of

the ease

of

obtaining a triggered display

in

this mode, the

p.p

AUTO trigger

mode

can be used for

most applications

and

the

remaining modes used only for

special applications

or

when stable triggering is

not

obtain·

able

in

this

mode

.

AUTO. When

the

AUTO push-button is illuminated, 8

triggered display is presented with

the

correct setting

of

the

LEVEUSLOPE control (see Trigger

Level

discussion)

whenever an adequate trigger signal

is

applied. The range

of

the LEVEL/SLOPE control

in

this

mode

is

fS

vertical divi-

sions. The TRIG'O light indicates when

the

display is trig·

gered.

When

the

trigger repetition rate

is

below

about

30

hertz

(or outside

the

frequency range selected by

the

COUPLING

switch)

or

when

the

trigger signal

is

inadequate. the sweep

free runs

at

the

sweep rate indicated by

the

TIME/DIV

switch

to

produce a reference trace

(TA

IG'O light off).

When an adequate trigger signal

is

again applied, the free-

running condition ends and a triggered display is presented.

When the LEVELISLOPE control

is

at

a setting outside

the

amplitude range

of

th

e trigger signal,

the

sweep also free

runs

at

the sweep

rate

indicated by the TIME/DIV switch.

This type

of

free-runn

ing

display can be useful

when

it

is

desired

to

measure only the maximum peak·to-peak ampli·

tude of a signal

without

observing the waveshape such

as

in

bandwidth measurements).

2·7

Operating

Instructions-Type

7B51

About

25%

C/"di"'

i'go

I~

/V

/"

V

,\

ifl

~

"

f\

I~

~

V

r\

I

r\

.r.

V\

l \

I~

.\

\.

IV

,

J

"\

~l

V

~

\

1\

\ \ , \

\1

1\1

\ V

\/

\

(A)

(B)

Fig. 2-5_

LEVEL/SLOPE

control

operation

for

(P-P)

AUTO

mode

triggering. (A)

LEVEL/SLOPE

control

set

so displayed

waveform

starts

at

about

25%

point

of

a one-division

waveform.

(B) displayed

waveform

still triggered

at

about

25%

of

leading edge,

when

signal

amplitude

is

increased,

to

produce

a four-division display

(LEVEL/SLOPE

control

at

same

setting

for

both

waveforms).

NORM. When

the

NORM

push-button

is

pressed, a trig-

gered display

is

presented with

the

correct setting

of

the

LEVEL/SLOPE control whenever an adequate trigger signal

is

applied. The range

of

the

LEVEL/SLOPE control

in

this

mode

is

±8

vertical divisions. The TRIG'D light indicates

when

the

display

is

triggered.

The

NORM

trigger mode must be used

to

produce trig-

gered displays with trigger repetition rates below

about

30

hertz. When

the

LEVEL/SLOPE control

is

at

a setting out-

side

the

amplitude range

of

the

trigger signal, when

the

trigger repetition rate

is

outside

the

frequency range selec-

ted by

the

COUPLING switch

or

when

the

trigger signal

is

inadequate, there

is

no trace (TRIG'D light off).

SINGLE

SWP.

When

the

signal

to

be displayed

is

not

repetitive

or

varies

in

amplitude, waveshape

or

repetition

rate, a conventional repetitive

type

display may produce an

unstable presentation. A stable display can often be obtain-

ed under these circumstances by using

the

single-sweep

feature

of

this unit. The SINGLE

SWP

MODE

is

also useful

to

photograph non-repetitive

or

unstable displays.

To obtain a single-sweep display

of

a repetitive signal,

first obtain

the

best possible display

in

the

NORM

MODE.

Then

without

changing

the

other

TRIGGERING controls,

press

the

SINGLE

SWP

pushbutton. When ready

to

view

the single-sweep display, press

the

RESET-READY push-

button_ A single trace

is

presented each time

the

RESET-

READY pushbutton

is

pressed

(as

long as

the

repetitive

signal remains connected

to

the

system and TRIGGERING

controls are correctly set) and further sweeps

cannot

be

presented until

the

RESET-READY pushbutton

is

pressed

again_

If

the

displayed signal

is

a complex waveform com-

2-8

posed

of

pulses

of

varying amplitude, successive single-

sweep displays may

not

start

at

the

same

point

of

the

wave-

~orm_

To avoid confusion due

to

the

CRT persistence, allow

the

display

to

decay before pressing

the

RESET-READY

pushbutton

again_

At

fast sweep rates, it may be difficult

to

view

the

single-sweep display_The apparent trace intensity

can be increased by reducing the ambient light

level

or

using a viewing hood as recommended

in

the

indicator

instruction manual.

Non-repetitive, random signals can be displayed

in

the

single-sweep mode by first obtaining

the

best possible dis-

play

in

the

NORM

MODE

with a signal which

is

about

the

same amplitude and frequency as

the

random signal. Then

without changing

the

other

TRIGGERING controls, press

the

SINGLE

SWP

pushbutton_ When ready for

the

random

signal, press

the

RESET-READY pushbutton_ The RESET-

READY pushbutton remains lighted

to

indicate

that

the

unit

has been reset and

is

ready

to

produce a

sweep_

The

light goes

out

after

the

random signal triggers

the

unit.

To

prepare

the

unit

for another single-sweep display, press

the

RESET-READY pushbutton again.

When using

the

single-sweep mode

to

photograph wave-

forms,

the

graticule must be photographed separately

in

the

normal manner

to

prevent over-exposing

the

film.

Be

sure

the camera system

is

well protected against stray light,

or

operate

the

system

in

a darkened room. For repetitive

waveforms, press the RESET-READY pushbutton only

once for each waveform unless

the

signal

is

completely

symmetrical. Otherwise, multiple waveforms may appear on

the

film. For random signals,

the

camera lens can be left

open until

the

random signal triggers

the

unit (RESET-

READY pushbutton lighted). Further information on

photographic techniques

is

given

in

the

camera instruction

manual.

Trigger Coupling

The pushbuttons located below

the

COUPLING title

(see

Fig. 2-4) select

the

method

in

which

the

trigger signal

is

connected

to

the

trigger circuits. The selected coupling

is

indicated by a lighted pushbutton. Each position permits

selection

or

rejection

of

the

frequency components

of

the

trigger signal which trigger

the

sweep. Fig. 2-6 graphically

illustrates the band of frequencies covered by each position

of the COUPLING switch.

AC.

In

the

AC

position

of

the

COUPLING switch,

the

DC

component

of

the

trigger signal

is

blocked. Signals with

low-frequency components below

about

30

hertz are atten-

uated.

In

general,

AC

COUPLING can be used for most

applications. However, if

the

signal contains unwanted fre-

quency components

or

if

the

sweep

is

to

be triggered

at

a

low repetition rate or

DC

level, one

of

the

remaining

COU·

PLiNG switch positions will provide a

better

display.

The triggering point in

the

AC

position depends upon

the average voltage

level

of

the

trigger signal.

If

the

trigger

signal occurs randomly,

the

average voltage level will vary,

causing

the

triggering

point

to

vary also. This shift of

the

triggering

point

may be enough so it

is

impossible

to

main-

tain a stable display.

In

such cases, use

DC

coupling.

WIDE

P-l'

AUTIl

•

IlIlIII¥I

•

S.fIIGU

J

I

•

.

IMW

Operating

Instructions-Type

7851

AC

LF REJ.

In

the

AC

LF REJ position,

DC

is

rejected

and low-frequency trigger signals below

about

30

kilohertz

are attenuated. Therefore,

the

sweep

is

triggered only by

the higher-frequency components of

the

trigger signal. This

position

is

particularly useful for providing stable triggering

if

the

trigger signal contains line-frequency components.

Also,

the

AC

LF

REJ position provides

the

best alternate-

mode vertical displays

at

fast sweep rates when comparing

two

or

more unrelated signals (with dual-trace vertical

or

slaved triggering operation for dual-vertical

unit

operation).

AC

HF REJ. The

AC

HF

REJ position passes

all

low-

frequency signals between

about

30

hertz and

50

kilohertz.

DC

is

rejected and signals outside

the

above range are atten-

uated. When triggering from complex waveforms, this posi-

tion

is

useful for providing stable display

of

the

low-

frequency compondnts.

DC.

DC

COUPLING can be used

to

provide stable trig-

gering with low-frequency signals which would be atten-

uated

in

the

other

modes,

or

with low-repetition rate

signals. It can also be used

to

trigger

the

sweep when

the

trigger signal reaches a

DC

level

selected

by

the

setting

of

the LEVEL/SLOPE

control

When using internal triggering,

the setting

of

the

vertical

unit

position controls affects

the

DC

triggering point.

30 Hz

30kHz

50

kHz

Fig.2-6. Frequency range

of

each COUPLING switch position.

® 2-9

Operating

Instructions-Type

7851

Trigger Source

The push

buttons

located below

the

SOU

RCE

title (see

Fig. 2-4) select

the

source of

the

trigger signal which

is

connected

to

the

trigger circuits. The selected source

is

indi-

cated by a lighted pushbutton.

INT.

In

the

INT position

of

the

SOURCE switch,

the

trigger signal

is

derived from

the

associated vertical unit.

Further selection of

the

internal trigger signal may be

provided by

the

associated vertical

unit

or

indicator oscillo-

scope; see

the

instruction manuals for these instruments for

information. For most applications,

the

INT-SOURCE posi-

tion can be used. However, some applications require

special triggering which

cannot

be obtained

in

the

INT-

SOURCE position.

In

such cases

L1NE-

or

EXT-SOURCE

must be used.

LINE. The LINE position

of

the

SOURCE switch

connects a sample

of

the

power-line voltage,

to

which

the

indicator oscilloscope

is

connected,

to

the

trigger circuit.

Line triggering

is

useful when

the

input signal

is

time-

related (multiple

or

sub-multiple)

to

the

line frequency. It

is

also useful for providing a stable display

of

a line-

frequency

component

in

a complex waveform.

EXT.

An

external signal connected

to

the

EXT TRIG

IN

connector can be used

to

trigger

the

sweep

in

the

EXT-

SOURCE position. The external signal must be time-related

to

the

displayed waveform for a stable display.

An

external

trigger signal can be used

to

provide a triggered display

when

the

internal signal

is

too

low

in

amplitude for correct

triggering

or

contains signal components on which it

is

not

desired

to

trigger. It

is

also useful when signal tracing

in

amplifiers, phase-shift networks, wave-shaping circuits, etc.

The signal from a single

point

in

the

circuit under test can

be

connected

to

the

EXT TRIG

IN

connector through a

probe

or

cable. The sweep

is

then triggered by

the

same

signal

at

all times and allows amplitude, time relationship

or

waveshape changes of signals

at

various points

in

the

circuit

to

be examined

without

resetting

the

TRIGGERING

controls.

EXT

-;-

10. Operation

in

the

EXT

-;-

10 position

is

the

same as described for EXT except

that

the

external signal

is

attenuated 10 times. Attenuation

of

high-amplitude exter-

nal trigger signals

is

desirable

to

broaden

the

range of

the

LEVEL/SLOPE control.

Trigger Slope

The LEVEL/SLOPE control determines whether

the

trigger circuit responds

on

the

positive-going

or

negative-

going portion

of

the

trigger signal. When

the

indicator line

on

the

outer

ring

of

the

LEVEL/SLOPE control

is

to

be left

of

center,

the

display starts on

the

positive-going portion

of

2-10

the waveform (notice positive-going waveform

to

left of

control. To

the

right of center,

the

display starts on

the

negative-going portion of

the

waveform (notice negative-

going waveform). The effect

of

the

LEVEL/SLOPE control

on

the

displayed waveform

is

shown

in

Fig. 2-7. When

several cycles

of

a signal appear

in

the

display,

the

selection

of

the

trigger slope

is

often unimportant. However,

if

only a

certain portion

of

a cycle

is

to

be displayed, correct setting

of

the

LEVEL/SLOPE control

is

important

to

provide a

display which starts on

the

desired slope

of

the

input signal.

Trigger Level

The LEVEL/SLOPE control determines

the

voltage level

on

the

trigger signal

at

which

the

display

is

triggered, as well

as selecting

the

trigger slope. The center knob

of

the

LEVEL/SLOPE control provides

about

a

3:

1 reduction in'

relation

to

the

outer indicator ring,

to

allow precise

level

selection. This control can also be

turned

throughout

the

complete

360

0 rotation

to

allow continuous triggering over

the selected slope. This

is

particularly useful

in

the

P-P

AUTO MODE. When

the

LEVEL/SLOPE control

is

set

to

the

"0"

on either

the

positive-going

or

negative-going wave-

form,

the

sweep

is

triggered near

the

zero-volt level

of

the

trigger signal. As

the

LEVEL/SLOPE control

is

rotated

away from

the

"0",

the displayed waveform starts

at

a

point

corresponding

to

the

position of

the

indicator line on

the associated slope waveform (within amplitude range of

trigger signal except

in

P-P

AUTO

MODE

which provides

triggered display throughout entire slope). For example

if

the

LEVEL/SLOPE control

is

turned clockwise from

the

"0"

on

the

positive-going slope,

the

displayed waveform

starts

at

a more positive level. Fig. 2-7 illustrates

the

opera-

tion

of

the

LEVEL/SLOPE control

at

different levels anc

slopes

of

a displayed waveform.

Before setting

the

triggering level, select

the

TRIG-

GERJ'NG SLOPE, MODE, COUPLING and SOURCE. Then

adjust

the

LEVEL/SLOPE control so

the

displayed wave-

form starts

at

the

desired point. The triggering slope can be

changed

at

any time by rotating

the

LEVEL/SLOPE con-

trol

to

the

corresponding

point

on

the

other

slope

waveform.

Horizontal Sweep Rate

The TIME/DIV switch provides 25 calibrated sweep

rates ranging from 0.05 microsecond/division

to

five

seconds/division. The VARIABLE TIME/DIV control must

be

in

the

calibrated position and

the

MAGNIFIER

at

X1

for

the

indicated sweep rate. The VARIABLE TIME/DIV

control incorporates a two-position switch

to

determine if

the

sweep rate

is

calibrated

or

uncalibrated.

When

the

VARIABLE knob

is

in

the

inward position,

the

VARI-

ABLE TIME/DIV control

is

inoperative and

the

sweep rate

is

calibrated. When pressed and released,

the

VARIABLE

knob moves outward

to

activate

the

VARIABLE TIME/

DIV

control for uncalibrated sweep rates. A calibrated

sweep rate can be obtained

at

any position

of

the

V

AR

1-

®

~~~---~-.--

,,------

@

Operating

Instructions-Type

7851

CRT

displays

obtained

with

LEVEL/SLOPE

control

in

positive-slope

region

1IIII'D

V

LEVEL/SLOPE •

f@~

THIn

V

LEVEL/SLOPE •

f@~

I--

f'

1

••••

II

I--

!'J

"

....

~

,I,

oSltlve

~(+I

slope

j

I

'f\

r\

7 \ \

I

'r

\J

f\7

\~

Positive

I-

(+1

slope

J

V

!I\

\

\.

1\

'r

T]

] W

,

I If\

r\

1\

II

\ \

1\

\

IV

,

I'

11\

r\

\ \

'y

\

\J J \

---------------------------------

Negative

THIrD\....

LEVEL/SLOPE -

1/-1

slope

7-

7

'\

r

....

~

\

'\

.\

'\ I 1 I

f@t~

'11

\ V U

CRT displays

obtained

with

LEVE L/SLOPE

control

in

negative-slope

region

TR!8'D

\....

LEVEL/SLOPE ,

@t~

7\

V

....

~

'}

\J

Negative

(-I

slope

J

17

~

\

,

I\J

lJ

Fig. 2-7. Effect

of

LEVEL/SLOPE

control

on

CRT

display (AUTO

POP

MODEl.

fa.

"

t\

'\'

1

f\

Ii

\

IV

n I

\.

~

\

IV

U

2-11

Tektronix 7B51 User manual

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