Tektronix 7a16a User manual

INSTRUCTION

MANUAL

7A16A

AMPL.IFIER

Serial Number

Tektronix,

In

c.

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one:

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0161

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77

2

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By

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WARRANTY

All

TEKTRONIX

in

struments are warranted against

defecti

ve

materials and workmanship for

one

year. Any

qu

estions with respect

to

the warranty should be

taken

up

with your TEKTRONIX Fie

ld

Engin

ee

r

or

represen

tat

ive.

All requests for repairs and replacement p

arts

should be

directed

to

the

TEKTRONIX Fie

ld

Office

Ot

representative

in

yo

ur

area.

Thi

s will assure you

the

fastest

po

ssi

ble

service. Please include the instrument

Type

Number

or

Pa

rt

Number and Serial

Number

with all requests for

part

s

or

service.

Specifications and price change privileges reserved.

Copyright @

1972

by Tektronix, Inc., Beave

rt

on, Oregon.

Printed

in

the

United

States

of

Contents

of

this publication may

not

be

reproduced in any

form

without

permission

of

Tektronix, Inc.

U.S.A. and foreign TEKTRONIX

products

covered by U.S.

and foreign

patent

s and

/o

r p

ate

nt

s pending.

TEKTRONIX is a registered trademark

of

Tektroni

x, Inc.

Scans

fIov

OlltsOIl'C~-OpliOlls

:::>

7A16A

TABLE

OF

CONTENTS

Page

SECTION'

SPECIFICATION

Introduction

1·'

Electrical Characteristics

'·1

Environmental Characteristics

'·2

Physical Characteristics 1·2

SECTION 2 OPERATING INSTRUCTIONS

Installation 2·1

Function

of

Controls and

Connectors

2·'

Basic Operation

2·2

General Operating Information

2·2

Applications

2·3

SECTION 3 CIRCUIT DESCRIPTION

Block Diagram Description 3·1

Detailed Circuit Description

3·'

SECTION 4 MAINTENANCE

Preventive Maintenance 4·1

Troubleshooting 4·1

Corrective Maintenance

4·3

SECTION 5 CALIBRATION

Performance Check 5·1

Test

Equipment

Required 5·1

Short

Form Procedure

5·2

Calibration Procedure

5·3

Balance

5·4

Gain

5·4

Compensation

5·5

Bandwidth and Risetime

5·6

SECTION 6 ELECTRICAL PARTS LIST

Abbreviations and Symbols

Parts Ordering Information

SECTION 7 DIAGRAMS AND CIRCUIT BOARD ILLUSTRATIONS

Symbols

and Reference Designators

SECTION 8 MECHANICAL PARTS LIST

Mechanical Parts List Information

I

ndex

of

Mechanical Parts Illustrations

Mechanical Parts List

®

Scans

bv

Oulsource-Opt;ons

=>

7A16A

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IWIOWlOTll

,

~

IMQ INPUT

20Pf

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tf"

~

I

Fig. 1·

1.

7A16A

Amplifier

Plug·in.

Scam bv

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=>

®

ArtekMedia

Digitally signed by ArtekMedia

DN: cn=ArtekMedia, o=ArtekMedia.com, ou,

[email protected], c=US

Date: 2008.11.16 17:47:24 -06'00'

L

..-

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Section

1-7A16A

SPECIFICATION

Introduction

The 7A16A Amplifier Plug-In Unit

is

a wide-bandwidth

amplifier designed for use with TEKTRON

IX

7000-Series

Oscilloscopes. The 7A16A can be operated

in

any plug·in

compartment of 7000·Series Oscilloscopes. Readout

encoding and trace identify functions are provided

to

readout equipped oscilloscopes.

Characteristics

Deflection

Factor

Calibrated Range

Accuracy

Uncalibrated (VARIABLE)

Gain Range

Frequency

Response

Bandwidth

AC Coupled (Lower Bandwidth Limit)

20

MHz Bandwidth

Step

Response

Risetime

20

MHz

Bandwidth

Risetime

Maximum

Input

Voltage

DC Coupled

AC Coupled

®

TABLE 1·1

ELECTRICAL

Performance

Requirements

5 mV/div

to

5 V/div,

10

steps in a 1·2·5

sequence.

Within

2%

of

indicated

deflection

factor

with

GAIN adjusted

at

10

mV/div.

Continuously

variable

between

calibrated steps;

extends

deflection

factor

to

at

least

12.5

V/div.

With 7400-Series With 7500-Series

60

MHz

90

MHz

With 7700-Series With 7900·Series

150

MHz

225

MHz

10

Hz

or

less.

With 7400-Series With 7500·Series

5.9

ns

3.9

ns

With 7700-Series With 7900·Series

2.4

ns 1.6 ns

Supplemental

Information

Permits

adjustment

of

deflection

factor

for

calibrated

operation

with

all 7000-Series main·

frames.

20

MHz, ±3 MHz.

21

ns

maximum.

250

V (DC + peak AC); A

component

500

V

pop

maximum,

1 kHz

or

less.

500

V (DC + peak AC); A

component

500

V

pop

maximum,

1 kHz

or

less.

1-1

Specification-7

A

16A

TABLE 1-1 (cont)

Characteristics

Performance

Requirements

Input

Rand

C

Resistance

Capacitance

Overdrive Recovery

Time

DC Drift

Drift

with

Time

(Ambient

Temp

and

Line Voltage

Constant)

Drift

with

Temperature

(Line

Voltage

Constant)

TABLE 1-2

ENVIRONMENTAL

CHARACTERISTICS

Refer

to

the

specifications

for

the

associated oscilloscope. Size

Weight

1-2

Supplemental

Information

1

Mn

±2%.

20

pF

±0.5

pF.

0.1 ms

or

less

to

recover

to

within

one

division

after

removal

of

overdrive signal

of

up

to

+75

div

or

-75

div regardless

of

overdrive signal

duration.

0.02

div

or

less in

anyone

minute

after

one

hour

warmup.

Not

more

than

0.02

div/"C.

TABLE 1-3

PHYSICAL

Fits all 7000-Series plug-in

compartments.

0.9

kg

or

1.9

Ibs.

®

Section

2-7A16A

OPERATING

INSTRUCTIONS

General

To

effectively use

the

7A

16A,

the

operation

and

capabilities

of

the

instrument

must

be

known.

This

section

describes

front-panel

control

functions,

general

information

on

signal

input

connections,

and

other

subjects

that

pertain

to

various

measurement

applications.

Installation

The

7A16A

is

calibrated

and

ready

for

use as received. It

can be installed in

any

compartment

of

TEKTRONIX

7000-Series Oscilloscopes,

but

is

intended

for

use

primarily

in

vertical plug·in

compartments.

To

install, align

the

upper

and

lower rails

of

the

7A

16A

with

the

oscilloscope

tracks

and

insert

the

plug-in.

The

front

panel will be flush

with

the

front

of

the

oscilloscope

when

the

plug-in

is

inserted,

and

the

latch

at

the

bottom-left

corner

will be in place against

the

front

panel.

To

remove

the

7A16A,

pull

on

the

latch (which

is

inscribed

with

the

unit

identification

"7

A

16A")

and

the

plug-in will

unlatch.

Continue

pulling

on

the

latch

to

slide

the

7A16A

out

of

the

oscilloscope.

Functions

of

Controls

and Connectors

Front

Panel

INPUT

Connector

Provides signal

connection

to

the

amplifier.

AC-GND-DC

Switch

Selects signal

input

coupling

mode.

AC:

The

AC

component

of

the

signal

is

coupled

to

the

input

while

the

DC

component

is

blocked.

DC:

Both

AC

and

DC

components

of

the

signal

is

coupled

to

the

amplifier

input.

GND:

Grounds

the

amplifier

input

while

maintaining

the

same

load

at

the

INPUT

connector.

Provides a

path

for

pre-charging

the

AC

coupling

capacitor

(this

feature

pro-

tects

both

the

7A

16A

and

the

source

generator

from

possible over-voltage

conditions).

®

POSITION

Controls

position

of

the

trace.

IDENTIFY

Pushbutton

Deflects

trace

about

0.3

division

for

trace

identification.

In

instruments

with

readout,

also replaces

readout

with

the

word

"10

ENTI

FY".

VOL

TS/DIV

Switch

Selects

calibrated

deflection

factors

from

5

mV

/div

to

5 V/div;

10

steps

in a 1-2-5

sequence.

VARIABLE

(VOL

TS/DIV)

Provides

continuously

variable

uncalibrated

settings

be·

tween

calibrated

steps.

Extends

the

deflection

factor

to

12.5

volts/division

or

more.

GAIN

Adjustment

Screwdriver

adjustment

permits

calibration

of

deflection

factor.

POLAR

ITY

Switch

Provides a

means

of

inverting

the

display.

+UP: A positive-going signal

at

the

INPUT

connector

deflects

the

CRT

display

upward.

INVERT:

A positive-going signal

at

the

INPUT con-

nector

deflects

the

CRT

display

downward.

BAN

DWI

DTH

Switch

Provides a

means

of

limiting

the

upper

bandwidth.

FULL:

Allows

the

7A16A

to

operate

at

full

rated

bandwidth.

20

MHz: Reduces

the

upper

bandwidth

of

the

7A16A

to

about

20

MHz.

2-1

Scans

by

Oulsource-Options

=>

Operation-7

A

16A

BASIC

OPERATION

General. This

procedure

demonstrates

the

use

of

the

connectors

and

controls

of

the

7A16A,

while

at

the

same

time

providing a means of checking

the

basic

operation

of

the

instrument.

Preliminary

Setup.

Install

the

7A

16A

into

any 7000-

series oscilloscope vertical

compartment

and

set

the

oscillo-

scope

VERTICAL

MODE and

TRIGGER

SOURCE

to

the

proper

settings.

Install a 7-series time-base

unit

into

a horizontal

compartment

and set

the

oscilloscope HOR IZONTAL

MODE

to

the

proper

setting.

Set

the

time-base

unit

to

a

sweep rate

of

one-millisecond per division

and

set

the

triggering

mode

to

AUTO.

Procedure

1.

Set

the

7A16A

AC-GND-DC switch

to

GND

and

position

the

trace

to

the

center

of

the

graticule.

2.

Set

the

VOLTS/DIV switch

to

10 mV

and

apply a

40

mV 1 kHz square-wave signal from

the

oscilloscope

CALIBRATOR

to

the

7A16A

INPUT

connector.

Set

the

AC-GND-DC switch

to

DC

and check

for

a four-division

display.

3. Set

POLARITY

switch

to

INVERT

and

check

that

the

displayed signal

is

inverted as

compared

to

its appear-

ance

in

step

2.

4.

Set

the

AC-GND-DC switch

to

AC

and

check

that

the

trace

is

centered

on

the

CRT

graticule.

GENERAL

OPERATING

INFORMATION

Signal Connections

In

general, probes

offer

the

most

convenient

means

of

connecting a signal

to

the

input

of

the

7A16A.

A lOX

attenuator

probe

offers a high impedance and allows

the

circuit

under

test

to

perform very close

to

normal

operating

conditions.

2-2

The

TEKTRONIX

P6053

probe

is

equipped

with a

readout

coding ring which

connects

to

a

circuit

in

the

amplifier unit. This

automatically

corrects

the

readout

displayed on

the

CRT

to

the

actual deflection

factor

at

the

tip

of

the

probe.

This

probe

is

recommended

for use with

the

7A

16A

and

an oscilloscope

equipped

with

readout.

The

TEKTRON

IX

P6054

probe

is

electrically identical

to

the

P6053

but

is

intended

for use with systems

not

equipped

with

readout.

For

more

information

refer

to

the

Tektronix,

Inc. catalog.

Vertical Gain Check and Adjustment

To

check

the

gain

of

the

7A16A,

set

the

VOLTS/DIV

switch

to

10

mV

and

connect

a

40

mV, 1 kHz signal from

the

oscilloscope

calibrator

to

the

Input

connector.

The

vertical deflection should be

exactly

four

divisions. If

not,

adjust

the

front

panel GAIN

for

exactly

four

divisions.

Input

Coupling

The

AC-GND-DC switch allows a choice

of

input

coupling

methods.

The

type

of

display desired

and

the

applied signal will

determine

the

coupling

to

use.

The

DC

coupling position can be used

for

most

applications. For AC signals with frequencies below

about

30

Hz

(10 Hz with a lOX

probe),

and

square waves whose

low-frequency

components

are

important

to

the

display, it

is

necessary

to

use

DC

coupling

to

obtain

a satisfactory

presentation.

In

the

AC coupling position

the

DC

component

of

the

signal

is

blocked by a

capacitor

in

the

input

circuit. The AC

coupling position provides

the

best

display

of

signals with a

DC

component

much larger

than

the

AC

component.

The

pre-charge

feature

should be used

when

there

is

a possibility

of

having a residual charge

on

the

input

capacitor

of

the

opposite

polarity

to

the

intended

input,

and

when

the

algebraic sum

of

the

com

bination

of

charges may be greater

than

the

maximum

input

limitations

of

the

amplifier.

To

use this

feature,

first

set

the

coupling switch

to

GND,

then

connect

the

probe

to

the

circuit

and

wait

about

two

seconds

for

the

coupling

capacitor

to

charge,

set

the

coupling switch

to

AC.

The

GND position provides a

ground

reference

at

the

input

of

the

amplifier

without

externally grounding

the

Input

connectors.

However,

the

signals

connected

to

the

inputs are

not

grounded,

and

the

same

DC

load

is

presented

to

the

signal source.

®I

Scans

bv

Outsource-Options

=>

VOLTS/DIV and

VARIABLE

The

amount

of

deflection

produced

by a signal

is

determined

by

the

signal

amplitude,

the

attenuation

factor

of

the

probe,

the

setting

of

the

VOL

TS/DIV

switch,

and

the

setting

of

the

VARIABLE

Control.

Calibrated

deflection

factors

represented

by

the

setting

of

the

VOL

TS/

DIV switch apply

only

when

the

VARIABLE

control

is

in

the

CAL position (pushed-in).

The

VAR IABLE

control

provides variable

uncalibrated

settings

between

the

calibrated

steps

of

the

VOL

TS/DIV

switch.

With

the

VARIABLE

control

out

set

fully

counter-

clockwise

the

uncalibrated

deflection

factor

is

extended

to

at

least 2.5 times

the

attenuator

setting.

By

applying a

cal

ibrated

voltage

source

to

the

INPUT

connector,

any

specific

deflection

factor

can

be set

within

the

range

of

the

VARIABLE

control.

Polarity Switch

The

POLAR ITY switch provides a

means

of

inverting

the

displayed signal. With

the

POLAR ITY

set

to

+UP, a

positive-going signal

at

the

INPUT

produces

an

upward

deflection

of

the

CRT

display. With

the

POLAR ITY

set

to

INVERT,

a positive-going signal will

produce

a

downward

deflection

of

the

CRT

display.

Trace Identification

When

the

IDENTIFY

button

is

pressed,

the

trace

is

deflected

upward

about

0.3

division

to

identify

the

7A

16A

trace.

This

feature

is

particularly

useful

when

multiple

traces are displayed

on

the

CRT.

In

mainframes

with

readout,

it also replaces

the

deflection

factor

readout

with

the

word

"IDENTIFY".

APPLICATIONS

General

The

following

information

describes

the

procedures

and

techniques

for making

measurements

with a 7A

16A

and

the

associated

TEKTRON

IX

oscilloscope

and

time-base. These

applications

are

not

described

in

detail, since each applica-

tion

must

be

adapted

to

the

requirements

of

the

individual

measurements.

This

instrument

can also be used for

many

applications

which are

not

described

in

this

manual.

Contact

your

local

TEKTRON

IX

Field Office

or

represent-

ative for assistance

in

making

specific

measurements

with

this

instrument.

Peak-to-Peak Voltage Measurements (AC)

To

make

peak-to-peak voltage

measurements,

use

the

following

procedure:

1. Apply

the

signal

to

the

I

nput

connector.

®

Operation-7

A

16A

2.

Set

the

Coupling switch

to

AC.

NOTE

For low-frequencv signals below about

30

hertz, use

the

DC

position to prevent attenuation

of

the

signal.

3.

Set

the

VOL

TS/DIV

switch

to

display

about

five

vertical divisions

of

the

waveform.

4.

Set

the

time-base Triggering

controls

for a stable

display.

Set

the

Time

Base

to

a sweep rate which displays

several cycles

of

the

waveform.

5.

Turn

the

7A16A

POSITION

control

so

the

lower

portion

of

the

waveform coincides

with

one

of

the

graticule

lines

below

the

center

horizontal

line,

and

the

top

of

the

waveform

is

within

the

viewing area. With

the

time

base

Position

control,

move

the

display so

one

of

the

upper

peaks lies near

the

center

vertical line (see Fig. 2-1).

6. Measure

the

divisions

of

vertical

deflection

peak

to

peak. Check

that

the

VARIABLE

control

is

in

the

CAL

position.

NOTE

This technique can also be used to make measure-

ments between two points on the waveform, rather

than peak to peak.

Vertical

deflection

J

__

_

'7

rJ

Position

to

center

vertical

line

\ \

\.

~--

---)

1 /

,

II

1\

I

\

IJ

~

Jr"\.

\ 7

"\

17

1\

J

\ j

Fig. 2-1. Measuring

the

peak·to-peak

voltage

of

a

waveform.

~

2-3

Scans bv

Outsource-Options

=>

Operation-7A16A

7. Multiply

the

distance measured in

step

7 by

the

VOLTS/D

IV

switch setting. Inelude

the

attenuation

factor

of

the

probe

if used.

EXAMPLE: Assume

that

the

peak

to

peak

vertical

deflection

is

4.5

divisions using a lOX

attenuator

probe,

and

the

VOLTS/D

IV

switch

is

set

to

1 V.

vertical

probe

Volts VOLTS/DIV

deflection

X X

attenuator

(divisions) setting

factor

Substituting

the

given values:

Volts Peak

to

Peak =

4.5

X 1 X

10

The

peak·to·peak

voltage

is

45

volts.

If

you

are using a 7A

16A

with a

coded

probe

and

an

oscilloscope

equipped

with

readout,

simply

multiply

the

distance measured

in

step

7 by

the

deflection

factor

displayed on

the

CRT.

Instantantous Voltage Measurements(DC)

To

measure

the

DC

level

at

a given

point

on a waveform,

proceed as follows:

1.

Connect

the

signal

to

the

Input

connector.

2.

Set

the

VOL

TS/DIV

switch

to

display

about

five

divisions.

3.

Set

the

Coupling switch

to

GND

and

position

the

trace

to

the

bottom

graticule line

or

other

reference line.

If

the

voltage

is

negative with respect

to

ground,

position

the

trace

to

the

top

graticule line. Do

not

move

the

POSITION

control

after

this reference line has been established.

NOTE

To

measure a voltage level with respect to another

voltage rather than ground, make the following

changes to Step 4.

Set

the Coupling switch to

DC

and

apply the reference voltage to the Input connector.

Then position the trace to the reference line and

disconnect the reference voltage.

4.

Set

the

Coupling switch

to

DC.

The

ground

reference

line can be

checked

at

any

time

by switching

to

the

GND

position.

5.

Set

the

time·base Triggering

controls

for

a stable

display.

Set

the

Time

Base sweep rate for an

optimum

display

of

the

waveform.

6. Measure

the

distance in divisions between

the

refer-

ence line

and

the

point

on

the

waveform

at

which

the

DC

level

is

to

be measured.

For

example,

in Fig.

2·2

the

measurement

is

between

the

reference line

and

point

A.

7. Establish

the

polarity

of

the

waveform. With

the

+UP/INV switch

in

the

+UP position,

any

point

above

the

reference line

is

positive.

8. Multiply

the

distance measured in

step

7 by

the

VOLTS/D

IV

switch setting. Inelude

the

attenuation

factor

of

the

probe,

if used.

EXAMPLE: Assume

the

vertical distance measured

is

4.6

divisions (see Fig. 2-2)

and

the

waveform

is

above

the

reference line using a lOX

probe

with a VOL

TS/DIV

switch

setting

of

0.5

V.

Using

the

formula:

Instan-

taneous

Voltage

vertical

distance X

polarity

X

(divisions)

Substituting

the

given values:

VOL

TS/

DIV

setting

probe

X

attenuation

factor

I

nstantaneous

Voltage =

4.6

X 1 X

0.5

V X

10

The

instantaneous

voltage

is

23

volts.

Point

A

"

!

V

--r--

--

---

--

-

Vertical

distance

J

____

\Reference

line

Fig. 2·2. Measuring

instantaneous

voltage with respect

to

same

reference.

2-4

REV.

JUNE

1974

®!

Scans

!Iv

Oulsource-Opt;ons

=>

Comparison Measurements

In

some

applications

it

may

be desirable

to

establish

units

of

measurement

other

than

those

indicated

by

the

VOLTS/DIV

switch.

This

is

particularly

useful

when

comparing

unknown

signals

to

a

reference

amplitude.

One

use

for

the

comparison-measurement

technique

is

to

facili-

tate

calibration

of

equipment

where

the

desired

amplitude

does

not

produce

an

exact

number

of

divisions

of

deflec-

tion.

The

adjustment

will be easier

and

more

accurate

if

arbitrary

units

of

measurement

are established, so

that

the

correct

adjustment

is

indicated

by

an

exact

number

of

divisions

of

deflection.

The

following

procedure

describes

how

to

establish

arbitrary

units

of

measure

for

comparison

measurements.

To

establish a vertical

deflection

factor

based

upon

a

specific

reference

amplitude,

proceed

as follows:

1.

Connect

the

reference

signal

to

the

Input

connector.

Set

the

time-base sweep rate

to

display several cycles

of

the

signal.

2.

Set

the

VOLTS/DIV

switch

and

the

VARIABLE

control

to

produce

a display which

is

an

exact

number

of

vertical divisions

in

amplitude.

Do

not

change

the

VARIABLE

control

after

obtaining

the

desired

deflection.

3.

To

establish an

arbitrary

vertical

deflection

factor

so

the

amplitude

of

an

unknown

signal can be

measured

accurately

at

any

setting

of

the

VOL

TS/DIV

switch,

the

amplitude

of

the

reference signal

must

be

known.

If

it

is

not

known,

it can be

measured

before

the

VARIABLE

control

is

set

in

step

2.

4.

Divide

the

amplitude

of

the

reference signal (volts)

by

the

product

of

the

vertical

deflection

(divisions)

established

in

step

2

and

the

setting

of

the

VOL

TS/DIV

switch.

®

Operation-7

A16A

This

is

the

vertical

conversion

factor.

Vertical

Conversion

Factor

reference

signal

amplitude

(volts)

vertical

deflection

X

VOL

TS/DIV

(divisions)

setting

5.

To

measure

the

amplitude

of

an

unknown

signal,

disconnect

the

reference signal

and

connect

the

unknown

signal

to

the

Input

connector.

Set

the

VOL

TS/DIV

switch

to

a

setting

that

provides

sufficient

vertical

deflection

to

make

an

accurate

measurement.

Do

not

re-adjust

the

VARIABLE

control.

6. Measure

the

vertical

deflection

in divisions

and

calculate

the

amplitude

of

the

unknown

signal using

the

following

formula:

Signal

Amplitude

VOL

TS/D

IV

vertical vertical

X

conversion

X

deflection

setting

factor

(divisions)

EXAMPLE:

Assume

a

reference

signal

amplitude

of

30

volts, a

VOLTS/DIV

setting

of 5 V

and

the

VARIABLE

control,

adjusted

to

provide a vertical

deflection

of

four

divisions.

Substituting

these

values in

the

vertical conversion

factor

formula

(step

4):

Vertical Conversion

Factor

30

V

4X5V

1.5

Then

with

a

VOL

TS/DIV

setting

of

2 V,

the

peak

to

peak

amplitude

of

an

unknown

signal which

produces

a vertical

deflection

of

five divisions can be

determ

ined by using

the

signal

amplitude

form

ula (step

6):

Signal

Amplitude

2 V X

1.5

X 5

15

volts

2-5

Scans

bv

Outsource-Options

=>

Section

3-7

A

16A

CIRCUIT

DESCRIPTION

Introduction

This section

of

the

manual contains a description

of

the

circuitry used

in

the

7A16A

amplifier.

The

7A16A

descrip-

tion

begins with a discussion

of

the

instrument

using

the

block diagram shown

in

the

Diagrams section.

Then,

each

circuit

is

described

in

detail using block diagrams

to

show

the

interconnections between stages

in

each major circuit

and

the

relationship

of

the

front-panel

controls

to

the

individual stages.

Complete schematics

of

each circuit are given

in

the

Diagrams section. Refer

to

these schematics

throughout

the

following circuit description for electrical values

and

relationship.

BLOCK

DIAGRAM

The signal

to

be displayed on

the

CRT

is

applied

to

the

INPUT

connector.

The signal passes

through

the

input

coupling switch, vyhere

the

appropriate

coupling

is

selected,

to

the

attenuators.

The VOL

TS/DIV

switch selects

the

correct

amount

of

attenuation

and

the

signal

is

passed

to

the

Input

Source Follower.

The Polarity Amplifier provides a

convenient

means of

inverting

the

displayed trace.

The

output

of

the

Polarity

Amplifier drives

the

2X

Gain Amplifier,

With

the

VOL

TS/DIV

switch set

to

the

5

mV

and

10 mV positions,

the

signal

connected

to

the

INPUT

connector

is

passed

through

the

attenuators

un-attended.

To

achieve a deflection

factor

of

5 mV/Div

the

gain

of

the

2X Gain Amplifier

is

increased from one

to

two.

Internal

gain

and

balance

adjustments

are included

in

the

amplifier.

Overall GAIN and VAR IABLE gain

is

adjusted

in

the

Gain Amplifier. Variable Balance and high frequency

adjustments

are also

controlled

in

the

Gain Amplifier. The

output

of

the

Gain Amplifier

is

connected

to

the

Posi-

tioning circuitry where

the

POSITION

and

IDENTI FY

functions are controlled.

The

Signal Splitter Amplifier provides differential signal

outputs

for

the

signal line

and

the

trigger line. This stage

contains a

bandwidth

limiter

that

limits

the

upper

frequen-

cy response

to

20 MHz.

®

The

output

of

the

Signal Splitter Amplifier

is

connected

to

the

oscilloscope mainframe via

the

interface

connector.

Readout

encoding circuitry used

in

the

7A

16A

is

standard

to

the

7000-Series.

DETAILED

CIRCUIT

DESCRIPTION

AC-GND-DC Switch

Input

signals

connected

to

the

INPUT

connector

can be

AC-coupled, DC-coupled,

or

internally disconnected.

S100A

is

a cam-type switch; a contact-closure

chart

showing

the

operation

is

given on

the

schematic diagrams.

When

the

AC-GND-DC switch

is

in

the

DC

position,

the

INPUT signal

is

connected

directly

to

the

attenuators.

In

the

AC position,

the

INPUT signal passes

through

capacitor

C10.

The

capacitor prevents

the

DC

component

of

the

signal from passing

to

the

amplifier.

The

GND position

opens

the

signal

path

and

connects

the

input

circuit

of

the

amplifier

to

ground. This provides a ground reference

without

the

need

to

disconnect

the

applied signal from

the

INPUT

connector.

Resistor R

102,

connected

across

the

AC-GND-DC switch, allows C10

to

be pre-charged in

the

GND position.

Input

Attenuator

The effective overall deflection factor

of

the

7A

16A

is

determined by

the

setting of

the

VOLTS/DIV switch,

S100B.

The

basic deflection

factor

is

5 millivolts per

division

of

CRT deflection.

To

increase

the

basic deflection

factor

to

the

values indicated on

the

front

panel, precision

attenuators

are switched

into

the

circuit. S100B

is

a

cam-type switch and

the

dots

on

the

contact-closure

chart

(see Diagram 1) indicate when

the

associated

contacts

are

in

the

position shown (open

or

closed).

In

the

5 mV/Div

and

10

mV/Div positions,

the

attenuators

are

not

used;

the

input

signal

is

connected

directly

to

the

Source Follower.

The

10

mV/Div position decreases

the

gain

of

the

2X Gain

Amplifier. For switch positions above ten millivolts per

division,

the

attenuators

are switched

into

the

circuit singly

or

in

pairs

to

produce

the

deflection

factor

indicated

on

the

front

panel. These hybrid

attenuators

are frequency-

compensated

voltage dividers. For

DC

and low-frequency

signals,

the

attenuators

are primarily resistance dividers and

at

high frequencies

the

attenuator

becomes primarily a

capacitive divider.

3-1

Circuit

Description-7A16A

In

addition

to

providing constant attenuation at all

frequencies

within

the

bandwidth

of

the instrument, the

input

attenuators

are

designed

to

maintain the

same

input

RC

characteristics (one megohm X 20

pF).

Each attenuator

contai

ns

an

adjustable

series

capacitor

to

provide correct

attenuation at high frequencies, and

an

adjustable·

shunt

capacitor

to

provide correct

input

capacitance.

Input

Source

Follower

Below

SN

B080000.

0150A

and

0140form

a cascode

amplifier

with

0150B

providing

a

constant

current.

R132

limits

the

current

drive

to

the

gate

of

0150A.

Dual-diode

CR130

provides

circuit

protection

by

limiting

the

voltage

swing

at

the

gate of Q

150A

to

about

±

14

volts. R

134,

C130,

and

the

capacitance

of

R

130

provide

low

frequency

com-

pensation.

Input

capacitance

for

the

5

mV

and

10

mV

positions

is set byC134.The

output

to

the

Polarity

Amplifier

(U350) is

from

the

source

of

0150A

and

high

frequencies

from

the

collector

of

0140.

R160

is used

to

balance

the

input

to

the

Polarity

Amplifier.

SN

B080000-Up.

0150A

is a source

follower

with

0150B

providing

a

constant

current.

R132

limits

the

current

drive

to

the

gate

of

0150A.

Dual-diode

CR130

provides

circuit

protection

by

limiting

the

voltage

swing

at

the

gate of

0150A

to

about

±1

0 volts. C130, C134, and

the

capacitance

of

R

130

provide

low

frequency

compensation.

Input

capacitance (or

the

5

mV

and

10

mV

positions

is set by

C130.The

output

to

the

Polarity

Amplifier

(U350) is

from

the

source

of

0150A.

C134

and

R134

form

a negative

resistance

network

.for

0150A.

Polarity

Amplifier

U350

is

a paraphase type

amplifier

with

a dual differen-

tial

output

capability. Polarity

of

the

output

is

selected by

gating the

control

bases

of

either the inverted

output

or the

un-inverted

output.

T301

is

a balun transformer and

provides

differential

drive

to

U350 at high frequencies.

C334 and RT334

thermally

compensate

for

gm

changes in

0150A.

2X

Gain

Amplifier

The

output

of

the Polarity

Amplifier

is

connected

to

a

gain switching

amplifier,

U450. The gain

of

U450

is

set by

the

control

bases,

pins

11

and 12. In the 5

mV

position,

full

drive

is

provided

to

the

following

stage

from

pins 6 and 8.

In the 10

mV

position, R413

sets

the

current

through

the

second

output

pair, pins 5 & 9. This

causes

the

emitter

currents

to

divide equally through R440, R442 and R501,

R503. R501, R503 provide the

only

drive

to

the

following

stage,

thus

forming

a

2X

gain

attenuator.

R436 provides

low

frequency thermal compensation. R453

(2X

Bal)

is

used

to

balance the

emitter

currents. CR507 and R507

maintains a constant

input

voltage while switching between

the 5

mV

and

10

mV

positions.

3-2

Gain

Amplifier

Integrated

circuit

U550

is

the

same

type

as

U350. Both

differential

outputs

of

U550

are

paralleled

to

provide drive

to

the

CAL

IN position R516

sets

the

gain

for

the entire

amplifier

by

adjusting the

current

at the

control

bases

of

U550. In the un-cal position the

VARIABLE

control,

R515, decreases the gain

of

the entire

amplifier

up

to

2.5 times.

RT539

compensates

for

temper-

ature variations. C531 and R531

are

high frequency adjust-

ments. DC balance over the

VARIABLE

range

is

adjusted

by R553.

Position

Circuit

Positioning

current

is

added

to

the signal

current

of

U550

output

from

the

current

sources

0720

and

0730.

R736 controls the voltage at the

bases

of

the

current

sources which in

turn

determines the

amount

of

positioning

current

added. When the

IDENTIFY

switch

is

closed the

current

through

0730

is

reduced causing the

CRT

trace

to

deflect.

Signal

Splitter

Amplifier

Integrated

circuit

U750

is

the

same

type

as

U450. The

two

differential

outputs

of

U750

are

connected

to

seperate

common

base

transistor amplifiers

to

provide seperate

display and trigger signals.

Both

outputs

of

U750

are

biased

equally

to

produce equal signal

outputs.

R770, C770, and

L770

are

high frequency compensation adjustments

for

the

display signal. L770

is

selected at the

factory

and need

not

be

changed unless U750,

0860,

or

0880

is

replaced.

0820, 0840,

0860,

and

0880

are

used

as

level shifters

to

return the DC level

of

the display signal

to

zero.

Amplifier

0820-0840

are

switched on when the

BAND-

WIDTH

switch

is

in the

full

position.

With

the

BAND-

WIDTH

switch in the 20

MHz

position

0860-0880

is

switched on. A

filter

in the collectors

of

0860-

0880

limit

the

bandwidth.

CR860

and

CR880 isolate the

filter

from

the

output

when in the

FULL

mode.

The trigger signal

circuitry

is

similar

to

the display signal

circuitry

with

0920

and

0940

as

level shifters

for

the

FULL

bandwidth position and

0960

and

0980

as

level

shifters

for

the 20

MHz

bandwidth

position.

Connectors

All

the connections made

to

the mainframe

by

the

7A

16A

are

shown on the connectors

portion

of

Diagram

2.

Also shown

are

the power supply decoupling components.

Readout Encoding

The Readout Encoding

circuit

consists

of

switching

resistors and probe sensing

stage

0620.

This

circuit

encodes

the

Rowand

Column

output

lines

for

readout

of

deflection

REV.

C,

MAR.

1975

factor,

uncalibrated

deflection

factor

(VARIABLE)

infor-

mation,

and signal inversion_ Data

is

encoded on these

output

lines

by

switching

resistors between

them

and the

time-slot

input

lines

or

by

current

added

through

0620.

R647-C647

are

switched between

time-slot

three (TS-3)

and

the

Column

output

line when

the

CAL

switch

is

in

the

un-cal

position.

This results in the

symbol>

(greater than)

being displayed preceding the

deflection

factor

readout.

R648

is

switched between TS-2 and the

Column

output

line

when the

POLARITY

switch

is

in the

INVERT

position.

This results in

the

symbol

f (inverted) being displayed

preceding

the

deflection

factor

readout.

Switching

resistors

are

used

to

indicate

the

setting

of

the

VOL

TS/DIV

switch

to

the

mainframe

readout

system.

The

dots

on

the

contact-closure

chart

(see

Diagram

Section)

indicate

when

the

associated

contacts

on

the

VOL

TS/DIV

cam

switch

are

closed. R633, R634,

and

R635

select

the

number

1, 2,

or

5

depending

on

the

combination

that

is

switched

in.

R638

and

R642

select

the

m

(milli)

prefix

in

the

5

mV

through

0.5

V

(500

mV)

positions

of

the

VOL

TS/DIV

switch.

R639

and

R643

select

the

V (volts)

symbol

in all

ranges. R630, R631,

and

the

output

of

the

probe

sensing

stage

(0620)

select

the

decimal

point

(number

of

zeroes).

again

depending

on

the

resistor

combination

switched

in

by

the

VOLTS/DIV

switch.

Probe sensing

stage

0620

identifies

the

attenuation

factor

of

the probe connected

to

the I

NPUT

connector

by

sensing

the

amount

of

current

flowing

through

the probe

coding resistor located in the probe

connector.

The

output

of

this

circuit

corrects the

mainframe

readout system

to

include the probe

attenuation

factor.

The

third

contact

of

the

INPUT

connector

provides

the

input

to

the probe

sensing device

from

the

probe coding resistance (coded

REV.

S,

MAR.

1975

Circuit

Description-7

A

16A

probes

only;

see

Operating

Instructions).

The

third

contact

is

also used

for

the

!DENTI

FY

input.

The coding resistor

forms

a voltage

divider

with

R621

through

CR621

to

the

-15

V supply. The resultant voltage

sets

the bias

on

0620

and determines the

collector

current,

along

with

emitter

resistor R622. When the

-15

volt

time-slot

pulse

is

applied

to

Interface

Connector

B33,

0620

is

interrogated and its

collector

current

is

added

to

the

column

current

output

through

Interface

Connector

A37.

With

a 1X probe (or no probe) connected

to

the

INPUT

connector,

0620

is

turned

off.

The

deflection

factor

readout

is

determined

by

the

VOL

TS/D

IV

switch

position.

With

a

10X

probe connected, the bias on

0620

allows

100

microamperes

of

collector

current

to

flow.

This increases

the

deflection

factor

readout

by

a

factor

of

10.

The

IDENTIFY

button

(S45 on Diagram 1) does

two

things when pressed:

1.

It

causes

the trace representing the 7A

16A

to

move

(see

the

discussion on the Position

Circuit).

2.

Forward

biases CR621 and

0620

to

result in a

sufficient

amount

of

collector

current

which

replaces the

deflection

factor

readout

with

the

word

"I

DENT

I

FY".

These

two

actions aid in

identifying

the 7A

16A

trace

when

multiple

traces

are

displayed. When the

IDENTIFY

button

is

released, the

deflection

factor

readout

is

restored.

For

further

information

on

the

operation

of

the readout

system,

see

the

oscilloscope

instruction

manual.

3-3

Scans

by Outsource-Options

=>

Section

4-7A16A

MAINTENANCE

Introduction

This section

of

the

manual contains maintenance infor-

mation for use

in

preventive maintenance, corrective

maintenance, and troubleshooting

of

the

7A16A.

Further

maintenance information relating

to

general

maintenance can be

found

in

the

instruction manuals for

the

7000-series oscilloscopes.

PREVENTIVE

MAINTENANCE

General

Preventive maintenance, consisting

of

cleaning, visual

inspection, etc., performed on a regular basis, will improve

the

reliability

of

this

instrument.

Periodic checks

of

the

semiconductor devices used

in

the

unit

are

not

recom-

mended

as

a preventive maintenance measure. See

semiconductor-checking information given under Trouble-

shooting.

Cleaning

Avoid the use

of

chemical cleaning agents which

might damage the plastics used

in

this instrument.

Special care should

be

taken when cleaning the

Polyphenylene Oxide attenuator board.

Do

not

apply

any solvent containing ketones, esters or halogenated

hydrocarbons.

To

clean, use only water soluble

detergents, ethyl,

methyl

or isopropyl alcohol.

Front

Panel. Loose

dust

may be removed with a

soft

cloth or a dry brush. Water and mild detergent may be

used; however, abrasive cleaners should

not

be used.

Interior. Cleaning

the

interior

of

the

unit

should precede

calibration, since

the

cleaning process could alter

the

settings

of

the

calibration adjustments.

Use

low-velocity

compressed air

to

blow off

the

accumulated

dust.

Hardened

dirt can be removed with a

soft,

dry

brush,

cotton-tipped

swab, or cloth dampened with a mild

detergent

and water

solution.

Lubrication

Use

a cleaning-type lubricant on shaft bushings, inter-

connecting plug

contacts,

and switch contacts. Lubricate

switch

detents

with a heavier grease. A lubrication kit

containing

the

necessary lubricating materials and

instructions

is

available through any TEKTRON

IX

Field

Office. Order TEKTRON

IX

Part Number 003-0342-01.

TROUBLESHOOTING

General

The following

is

provided

to

augment information

contained

in

other

sections

of

this manual when trouble-

shooting

the

7A16A. The schematic diagrams, circuit

description, and calibration sections should be used

to

full

advantage. The circuit description section gives detailed

information on circuit behavior and

output

requirements.

Troubleshooting Aids

Diagrams. Circuit diagrams are given on

foldout

pages

in

Section 7. The circuit number and electrical value of each

component

in

this

instrument

are shown on

the

diagrams.

Important

voltages are also shown.

Circuit Boards. The circuit boards used

in

the

7A16A are

outlined on

the

schematic diagrams, and photographs

of

the

boards are shown on

the

backs

of

the

schematic diagrams.

Each board-mounted electrical

component

is

identified on

the

photograph by its circuit number.

Component

and Wiring Color Code. Colored stripes or

dots on resistors and capacitors signify electrical values,

tolerances, etc., according

to

the

E

IA

standard color code.

Components

not

color coded usually have

the

value printed

on

the

body.

The insulated wires used for interconnection

in

the

7A16A are color coded

to

facilitate tracing wires from one

point

to

another

in

the

unit.

Semiconductor

Lead Configuration. The lead configu-

rations

of

the

semiconductor devices used

in

this instru-

ment

are shown on

the

schematic diagrams.

®I

REV.

JUNE

1974

4-1

Maintenance-7

A

16A

Troubleshooting

Equipment

The following

equipment

is

useful for troubleshooting

the

7A16A.

1. Semiconductor

Tester-Some

means of testing

the

transistors, diodes, and FET's used

in

this instrument

is

helpful. A transistor·curve tracer such

as

the

TEKTRON IX

Type

576

will give

the

most

complete information.

2.

DC

Voltmeter and

Ohmmeter-A

vol,tmeter

is

re-

quired for checking voltages within

the

circuits, and an

ohmmeter

for checking resistors and diodes.

3. Test

Oscilloscope-A

test oscilloscope

is

required

to

view waveforms

at

different points

in

the

circuit. A

TEKTRONIX 7000-series Oscilloscope equipped with a

readout

system,

7013

Digital Multimeter

unit,

7B-series

Time-Base unit, and a 7A-series Amplifier

unit

with a 10X

probe will meet

the

needs

of

both

items 2 and 3.

4.

Plug-in

Extender-A

fixture

that

permits operation

of

the

unit

outside of

the

plug-in

compartment

for better

accessibility during troubleshooting. Order TEKTRONIX

Part Number 067-0589-00.

Troubleshooting Procedure

This troubleshooting procedure

is

arranged

in

an order

which checks

the

simple trouble possibilities before pro-

ceeding with extensive troubleshooting.

1. Check Control Settings. An incorrect setti

ng

of

the

7A16A controls can indicate a trouble

that

does

not

exist.

If

there

is

any question

about

the

correct

function or

operation of a control or front-panel

connector,

see

the

Operating Instructions section.

2. Check Associated Equipment. Before proceeding

with troubleshooting of

the

7A16A check

that

the

equipment

used with this

instrument

is

operating correctly.

If

possible,

substitute

an amplifier

unit

known

to

be

operating correctly

into

the

indicator

unit

and see if

the

problem persists. Check

that

the

input

signals are properly

connected

and

that

the

interconnecting cables are

not

defective.

3.

Visual Check. Visually check

the

portion

of

the

instrument

in

which

the

trouble

is

suspected. Many troubles

can be located by visual indications, such

as

unsoldered

connections, broken wires, damaged circuit boards,

damaged

components,

etc.

4-2

4. Check

Instrument

Performance. Check

the

calibra-

tion

of

the

unit

or

the

affected circuit, by performing

Performance Check

of

Section 5. The

apparent

trouble may

only be a result

of

mis-adjustment, and may be corrected

by calibration. Complete calibration instructions are given

in

Section 5.

5. Check Voltages. Often

the

defective

component

or

stage can be located by checking for

the

correct

voltage

in

the

circuit. Typical voltages are given on

the

diagrams;

however, these are

not

absolute and may vary slightly

between instruments. To obtain operating conditions

similar

to

those used

to

take these readings, see

the

instructions

in

the

Diagram section.

6.

Check Individual Components. The following

methods are provided for checking

the

individual com-

ponents. Components which are soldered

in

place are best

checked by disconnecting one end

to

isolate

the

measure-

ment

from

the

effects

of

surrounding circuitry.

NOTE

To

locate intermittent or temperature sensitive com-

ponents

mounted

on the attenuator board, Quik

Freeze (Miller Stephenson, MS-240, TEKTRONIX

Part Number 006-0173-01)

is

recommended. Dry ice

or dichlordi-fluorremethane (Freon 12, Dupont or

Can-a-Gas)

may

also be used. Other types

of

circuit

coolant

may

damage the polyphenylene oxide boards.

A. TRANSISTORS. The best check

of

transistor opera-

tion

is

actual performance under operating conditions.

If

a

transistor

is

suspected of being defective, it can best

be

checked by substituting a

component

known

to

be good;

however,

be

sure

that

circuit conditions are

not

such

that

a

replacement might also be damaged.

If

substitute

transistors

are

not

available, use a dynamic tester (such

as

TEKTRONIX

Type

576). Static-type testers may be used,

but

since

they

do

not

check operation under simulated

operating conditions, some defects may go unnoticed.

Be

sure

the

power

is

off

before

attempting

to

remove

or

replace

any transistor.

B.

DIODES. A diode can be checked for an open

or

for

a

short

circuit by measuring

the

resistance between termi-

nals with an

ohmmeter

set

to

the

R X 1k scale. The diode

resistance should be very high

in

one direction and very low

when

the

meter leads are reversed.

Do

not

check tunnel

diodes

or

back diodes with

an

ohmmeter.

Do

not

use an ohmmeter scale thathas a high internal

current.

High

currents

may

damage the diodes.

REV. B,

MAR.

1975

C. RESISTORS. Check resistors with an

ohmmeter.

Resistor

tolerance

is

given in

the

Electrical Parts List.

Resistors normally

do

not

need

to

be replaced unless

the

measured value varies widely from

the

specified value.

D.

CAPACITORS. A leaky

or

shorted

capacitor

can be

detected

by checking resistance with an

ohmmeter

on

the

highest scale. Use an

ohmmeter

which will

not

exceed

the

voltage rating

of

the

capacitor.

The

resistance reading

should

be high

after

initial charge

of

the

capacitor.

An

open

capacitor

can best be

detected

with a

capacitance

meter,

or

by checking

whether

the

capacitor

passes AC signals.

7.

Repair and

Readjust

the

Circuit.

Special

techniques

required

to

replace

components

in this

unit

are given

under

Component

Replacement.

Be

sure

to

check

the

perform-

ance

of

any

circuit

that

has been repaired

or

that

has

had

any

electrical

components

replaced. Recalibration

of

the

affected

circuit

may be necessary.

CORRECTIVE

MAINTENANCE

General

Corrective

maintenance

consists

of

component

replace-

ment

and

instrument

repair. Special

techniques

required

to

replace

components

in this

instrument

are given here.

Obtaining Replacement Parts

Standard

Parts.

All

electrical

and

mechanical

part

re-

placements

for

the

7A16A

can be

obtained

through

your

local

TEKTRON

IX

Field Office

or

representative. However,

many

of

the

electronic

components

can be

obtained

locally

in less

time

than

is

required

to

order

them

from

Tektronix,

Inc. Before purchasing

or

ordering

replacement

parts,

check

the

parts list for value,

tolerance,

rating

and

description.

NOTE

When selecting replacement parts,

it

is

important

to

remember

that

the

physical

size

and

shape

of

a

component

may

affect

the

performance

of

the

instrument,

particularly

at

high

frequencies.

All

re-

placement

parts

should

be

direct

replacements unless

it

is

known

that

a

different

component

will

not

adversely

affect

instrument

performance.

Special Parts.

In

addition

to

the

standard

electronic

components,

some

special

parts

are used

in

the

7A16A.

These parts are

manufactured

or

selected by

Tektronix,

Inc.

in

accordance

with

our

specifications. These special parts

are indicated

in

the

parts

list by an asterisk preceding

the

part

number.

Most

of

the

mechanical

parts

used

in

this

instrument

have been

manufactured

by

Tektronix,

Inc.

Maintenance-7A16A

Order

all special parts

directly

from

your

local

TEKTRONIX

Field Office

or

representative.

Ordering Parts. When ordering

replacement

parts

from

Tektronix,

Inc., include

the

following

information:

1.

Instrument

Type.

2.

Instrument

Serial Number.

3.

A

description

of

the

part

(if electrical, include

circuit

number).

4.

TEKTRONIX

Part

Number.

Soldering Techniques

[

WARNING

I

Disconnect the

instrument

from

the

power

source

before

soldering.

Attenuator

Circuit

Board.

The

Attenuator

Circuit Board

is

made

from

polyphenylene

oxide

because

of

its excellent

electrical characteristics. Use

more

than

normal care when

cleaning

or

soldering this material. The following rules

should

be observed

when

removing

or

replacing parts:

1. Use a low-wattage soldering iron

(not

over

15

watts).

2. Do

not

apply

more

heat,

or

apply

heat

for

a longer

time,

than

is

absolutely

necessary.

3.

Use

some

form

of

vacuum

solder

remover

when

removing multi-lead devices.

4.

Do

not

apply

any

solvent

containing

ketones, esters

or

halogenated

hydrocarbons.

5.

To

clean, use

only

water-soluble

detergents,

ethyl,

methyl

or

isopropyl alcohol.

Circuit

Boards

(except

Attenuator

board).

The

com-

ponents

mounted

on

the

circuit

boards

in

the

amplifier

can

be replaced using normal

circuit

board

soldering

techniques.

Keep

the

following

points

in

mind when soldering

on

the

circuit

boards:

1.

Use

a pencil-type soldering iron

with

a (wattage)

rating from

15

to

50

watts.

4-3

Scans

by

OutsouTce-Opt;ons

=>

Maintenance-7

A

16A

2. Apply

heat

from

the

soldering iron

to

the

junction

between

the

component

and

the

circuit

board.

3.

Heat-shunt

the

lead

to

the

component

by means

of

a

pair

of

long-nose pliers.

4.

Avoid excessive heating

of

the

junction

with

the

circuit

board,

as

this

could

separate

the

circuit

board

wiring

from

the

base material.

5. Use electronic grade

60-40

tin lead solder.

6.

Clip

off

any

excess lead length extending

beyond

the

circuit

board.

Clean

off

any residual flux with a flux-

removing solvent.

Metal Terminals. When soldering metal terminals (po-

tentiometers,

etc.) use

60-40

tin-lead solder and a

15

to

50

watt

soldering iron. Observe

the

following

precautions

when soldering metal terminals:

1. Apply only enough

heat

to

make

the

solder flow

freely.

2. Apply

only

enough solder

to

form a solid con-

nection. Excess solder may impair

the

function

of

the

part.

3.

If a wire

extends

beyond

the

solder joint, clip

off

the

excess.

4. Clean

the

flux from

the

solder

joint

with a flux-

removing solvent.

Component

Replacement

I

WARNING

I

Disconnect the

equipment

from

the

power

source

before

replacing components.

Semiconductor

Replacement.

Transistors should

not

be

replaced unless actually defective.

If

removed from their

sockets during

routine

maintenance,

return

them

to

their

original sockets. Unnecessary

replacement

of transistors

may

effect

the

calibration

of

this

instrument.

When

transistors are replaced,

check

the

performance

of

the

part

of

the

instrument

wh ich may be

affected.

4·4

Replacement

semiconductors

should be

of

the

original

type

or

a

direct

replacement.

The

schematic diagram shows

the

lead configurations

of

the

semiconductors

used in this

instrument.

If

the

replacement

semiconductor

is

not

of

the

original

type,

check

the

manufacturer's

basing diagram for

proper

basing.

Circuit

Board Removal

In

general,

the

circuit

boards used

in

the

7A16A

need

never be removed unless

they

must

be replaced. Electrical

connections

to

the

boards are

made

by soldered con-

nections.

If

it

is

necessary

to

replace a

circuit

board

assembly, use

the

following procedures.

A. READOUT CIRCUIT BOARD REMOVAL

1. Disconnect

the

wires

connected

to

the

outside

of

the

board.

2. Remove

the

seven screws holding

the

board

to

the

mounting

surface.

3.

Disconnect

the

wires

connected

to

the

inside

of

the

board.

4.

Remove

the

board from

the

unit.

5.

To

replace

the

board,

reverse

the

order

of

removal.

B.

ATTENUATOR

CIRCUIT BOARD REMOVAL

1. Remove

the

readout

board

as

outlined in

the

2. Disconnect

the

inductor,

capacitor,

and

two

ground

straps

connected

to

the

rear

of

the

board.

3.. Loosen

the

front

set

screw

on

the

VAR IABLE

control

shaft

coupling (use a 0.050-inch hex-key wrench).

4.

Remove

the

red VAR lAB

LE

control

knob

and

glass

rod from

the

control

shaft.

5. Remove

the

remaining front-panel knobs using a

1116-inch hex-key wrench.

6.

Remove

the

front

panel from

the

instrument

by

prying

at

center

bottom

with screwdriver.

®

Scam

bv

Outsource-Options

=>

7. Remove

the

attenuator

shields.

8. Disconnect

the

wires and resistor from

the

INPUT

BNC

connector.

9. Remove

the

INPUT BNC

connector.

10.

Remove

the

attenuator

board with cam switch from

the

instrument.

11. Replace by reversing

the

Removal Procedures.

C.

AMPLIFIER CIRCUIT BOARD REMOVAL

1. Remove

the

plastic plug-in guide from

the

rear

of

the

instrument.

2. Disconnect

the

wires

connected

to

the

board from

the

front-panel controls.

3.

Loosen

the

hex·socket

screw

in

the

coupling

of

the

VAR lAB

LE

control

shaft

using a 0.050-inch hex-key

wrench. Pull

the

VARIABLE

knob

and glass shaft from

the

front

of

the

instrument.

4.

Disconnect

the

inductor,

capacitor, and

two

ground

straps from

the

front

of

the

board.

5. Remove

the

screws and

nuts

securing

the

board

to

the

chassis

or

other

mounting

surface.

6.

Remove

the

board from

the

instrument.

7.

To

replace, reverse

the

order

of

removal.

Switch Replacement

Several types

of

switches are used

in

the

7A16A. The

slide and micro switches should be replaced

as

a

unit

if

damaged. The following special maintenance information

is

provided for

the

cam·type

switches.

®

Maintenance-7A16A

~

Repair

of

cam-type switches

should

be undertaken

only

by

experienced maintenance personnel.

Switch

alignment

and

spring tension

of

the contacts

must

be

carefully

maintained

for

proper

operation

of

the

switch.

For

assistance

in

maintenance

of

cam-type

switches,

contact

your

local

TEKTRONIX

Field

Office

or

representative.

A. CAM·TYPE SWITCHES

A

cam-type

switch consists

of

a rotating

cam,

which

is

turned

by

the

front·panel knobs, and a set

of

contacts

mounted

on an adjacent circuit board. These switch

contacts

are

actuated

by

lobes on

the

cam.

The

VOL

TS/

DIV

and

AC-GND·DC (coupling) cam-type switches can be

disassembled for inspection, cleaning, repair, or replace·

ment

as follows:

1. Remove

the

Readout

board and

the

Attenuator

board/switch assembly

as

described previously.

The

front

switch section on

the

Attenuator

board

is

the

AC-GND-DC

switch and

the

rear switch section

is

the

VOL

TS/DIV

switch. The switches are now

open

for inspection or

cleaning.

2.

To

completely remove

the

switch from

the

board,

remove

the

two

screws and

four

hexagonal posts which

hold

the

cam-type switch

to

the

circuit board.

3.

To

remove

the

cam from

the

front

support

block,

remove

the

retaining ring from

the

shaft

on

the

front

of

the

switch and slide

the

cam

out

of

the

support

block.

Be

careful

not

to

lose

the

small

detent

roller.

4.

To

replace defective switch

contacts,

follow

the

instructions given

in

the

switch repair kit.

5.

To

re-install

the

switch assembly, reverse

the

above

procedure.

Recalibration After Repair

After any electrical

component

has been replaced,

the

calibration

of

that

particular circuit should be checked,

as

well as

the

calibration of

other

closely related circuits.

Refer

to

Section 5

for

th ese procedures.

4-5

Scans

by

OutsollTce-Options

=>

Tektronix 7A16A User manual

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