Tektronix 7a15a User manual

•

I.

I

•

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••

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I·

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INSTRUCTION

MANUAL

Seriol

Number

·

__

7A15A/AN

AMPLIFIER

Tektronix,

Inc

. • P. O . 80K

500

• B

eo

ver

lon,

Oregon

97005

•

Phone

6<14

-0 161 •

Cobles

: Tektr

onix

070-1210-00 871

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WARRANTY

All

Tektronilt inltfUments are warranted against

defective material, and workmanship for

one

year.

Any

questiom

with

respect

to

the

warranty.

mentioned above, should be taken

up

with

your

Tektroni)( Field

En

l

;"

'!:.t.llf..!'

,

p,·

e.e'll'J

~~

e.

____

_

All

requests rep.irs and parts

should

to-th

e

Tektr

onix Office

representitii"e in

your

-.

This

pr~rt"l1

~

you

the

fatest

pos$ible service. P

JMee

include the

Number) .iKI Serial

or

Specifications

ar

price change

pri\/i'

~es

reserved.

Copyright ® 1971

by

Tektronix, Inc., Beaverton,

Oregon. Printed in the United

Sta

tes of America. All

rights reserved.

Co

nt

ents

of

thi

s

publication

may

not

be

reproduced

in arl V

form

without

permission

of

th

e

co

pyright

owner

.

U.S.A. and foreign Tektronix

products

covered

by U.S.

and

foreign

patent

s

and/or

pat

ents

pending.

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7A15A/7A15AN

TABLE

OF

CONTENTS

SECTION 1 SPECIFICATION

Introduction

Electrical Characteristics

Environmental Characteristics

Physical Characteristics

SECTION 2 OPERATING INSTRUCTIONS

SECTION 3

SECTION 4

Installation

Controls

and

Connectors

Basic

Operation

General Operating

Information

Applications

CIRCUIT DESCRIPTION

I

ntrod

uction

Block Diagram Description

Detailed Circuit Description

MAINTENANCE

Preventive Maintenance

Troubleshooting

Corrective Maintenance

REV.

B, OCT.

1974

Page

1-1

1-2

2-1

2-2

2-3

3-1

4-1

4-3

SECTION 5 CALIBRATION

Introduction

Test

Equipment

Required

Performance

Check

Procedure

Calibration

Procedure

SECTION 6 ELECTRICAL

PARTS

LIST

Abbreviations

and

Symbols

Parts Ordering

Information

SECTION 7 DIAGRAMS AND CIRCUIT BOARD

I

llUSTRA

TlONS

Symbols

and

Reference Designators

SECTION 8 MECHAN

ICAl

PARTS

LIST

Mechanical Parts List

Information

Index

of

Mechanical Parts

Illustrations

Mechanical Parts List

Page

5-1

5-2

-

.-

--

•

~-

I·

~

. " -•

0

"""'fiT

__

•

••

-

-"-

•

-

~

~.

I

·~

. "

..

•

1fIVt'" _ e

--

-•

Fig. 1-1.

7A1

5A .

nd

7

A1

5AN Am

pl

if..... •

••

7A15

A/AN

® •

ArtekMedia

Digitally signed by ArtekMedia

DN: cn=ArtekMedia, o=ArtekMedia.com, ou, [email protected],

c=US

Date: 2008.11.16 17:36:11 -06'00'

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Introduction

SECTION

1

SPECIFICA

TION

7A15A/7A15AN

7A

15A/7

A15AN

can

be

operated

in

any

plug-in

compart-

ment

of

7000-Series oscilloscopes.

The

7A

15A/7

A15AN Amplifier plug-in

unit

is

a wide

band amplifier designed

for

use with

Tektronix

7000-Series

oscilloscopes.

The

7A

15A

and

7A15AN

,are

electrically

identical

except

that

encoding capabilities and an

"IDENTIFY"

function

are provided in

the

7A15A.

The

following electrical characteristics are

val

id

over

the

stated

environmental range

for

instruments

calibrated

at

an

ambient

temperature

of

+20°C

to

+30°C,

and

after

a five

minute

warmup

unless otherwise

noted.

-Characteristic

Deflection

Factor

Calibrated Range

Deflection

Factor

Accuracy

Uncalibrated (VAR IABLE)

X10

GAIN

Frequency

Response

Upper

Bandwidth

Frequency

(at

-3

dB)

X1 (System

Dependent)

X10

Low-Frequency Response

(Lower

-3

dB point)

AC (Capacitive)

coupled

®

TABLE 1-1

ELECTRICAL

Performance

Requirement

5 mV/Div

to

10

V/Div,

11

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

25

V/Div

Increases amplifier gain by a

factor

of

10

within 10%, decreasing

deflection

factor

to

500

JlV

/D

iv

With 7900-series With nOO-series

80

MHz

75

MHz

With 7500-series With 7400-series

60

MHz

50

MHz

10

MHz

10Hz

or

less

without

probe

1 Hz

or

less

with

probe

Supplemental

Information

,-,

I

Specification-7

A

15An

A

15AN

TABLE

1-1

-Characteristic Performance

Req

Supplementalln/o,m.';on

.-

(cont)

uirement

-

Maximum

Input

Voltage

===F===========

I

DC

Coupled

AC Coupled

II

nput

Rand

C

Resistance 1

Mn

±

2%

Capacitance Approximately 20.0

pf

RC

Tolerance

Overdrive Recovery Time

-

TABLE

1-2

ENVIRONMENTAL

CHARACTERISTICS

IRefer

to

the specifications

for

the associated oscilloscope I

1-2

250 V (DC +

Peak

AC); AC component

500 V

P-P

maximum, 1 kHz or

less

500 V (DC +

Peak

AC);

AC component

500 V

P-P

maximum, 1 kHz or

less

Within ± 1% between all deflection

factors.

0.1

ms

or

less

to

recover

to

within

one

division after removal

of

overdrive signal

of

up

to

+75 divisions

to

-75

divisions

regardless

of

overdrive signal duration

TABLE

1-3

I

PHYSICAL

.1

---r----_

Size

Fits all 7000-series plug·in compartments

Weight 1 pound 13 ounces (0.82 kilogram)

®

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7A15A/7A15AN

SECTION

2

OPERA

TING

INSTRUCTIONS

General

To

effectively use

the

7A

15A/7

A

15AN,

the

operation

and capabilities

of

the

instrument

must

be

known.

This

section

dE!scribes

front-panel

control

functions,

general

information

on

signal

input

connections,

and

other

subjects

that

pertain

to

various

measurement

applications.

Installation

The

7A15A/7A15AN

is

calibrated

and ready for use as

received. It can be installed

in

any

compartment

of

Tek-

tronix

7000-Series Oscilloscopes,

but

is

intended

for

use

primarily

in

vertical plug-in

compartments.

To

install, align

the

upper

and lower rails

of

the

7A15A/7A15AN

with

the

oscilloscope

tracks

and insert

thE!

plug-in.

The

front

panel

will be flush with

the

front

of

the

oscilloscope

when

the

7A15A/7A15AN

is

fully inserted,

and

the

latch

at

the

bottom-left

corner

will be

in

place against

the

front

panel.

To

remove

the

7A15A/7Al!5AN,

pull

on

the

latch

(which

is

inscribed

with

the

unit

identification

"7

A

15A"

or

"7A15AN")

and

the

7A15A/7A15AN

will

unlatch.

Continue

pulling

on

the

latch

to

slide

the

7A15A/7A15AN

out

of

the

oscilloscope.

VOLTS/DIV

VARIABl.E

FRONT

PANEL

CONTROLS

AND

CONNECTORS

Selects calibrated

deflection

factors

from

5 mV/Div

to

10

V/Div;

11

steps

in a 1-2-!i sequence.

Provides

continuously

variable un-

calibrated

settings

between

calibrated steps.

Extends

the

deflec-

t

ion

factor

range

to

25

volts/

division

or

more.

GAIN

Adjustment

Screwdriiver

adjustment

permits

calibration

of

deflection

factor.

MAG

I

nput

Connector

AC-GND-DC

INVERT:

A positive-going signal

at

the

Input

connector

deflects

the

CRT

display

downward.

Provides

means

of

decreasing

the

deflection

factor.

Xl:

Deflection

factor

is

that

selected

by

VOL

TS/DIV

and

VARIABLE

controls.

Xl0

REDUCED

BANDWIDTH:

Deflection

factor

is

one-tenth

of

the

value selected by

the

VO L

TS/

DIV and

VARIABLE

controls.

Provides signal

connection

to

the

amplifier.

Selects signal

input

coupling

mode.

AC:

The

AC

component

of

the

signal

is

coupled

to

the

amplifier

input,

while

the

DC

component

is

blocked.

DC:

Both

AC and

DC

components

of

the

signal are

coupled

to

the

amplifier

input.

GND:

Grounds

the

amplifier

input

while maintaining

the

same load for

the

input

signal. Provides a charge

path

for

the

AC

coupling

capacitor

to

pre-charge

the

input

circuit

before

switching

the

input

to

AC.

I

POLARITY

I·

Provides means

of

inverting

the

display.

POSITION

IDENTIFY

(7A15A

Only)

Controls

position

of

the

trace.

Deflects

trace

about

0.3

division

for

trace

identification.

In

instruments

with

readout,

also replaces

readout

with

the

word

"IDENTIFY".

I ®

+UP: A positive-going signal

at

the

Input

connector

deflects

the

CRT

display

upward.

2-1

Operating I

nstructions-7

A

15A/J

A15AN

BASIC OPERATION

General. This

procedure

demonstrates

the

use

of

the

connectors

and

controls

of

the

7A15A/7A15AN,

while

at

the

same

time

providing a means

of

checking

the

basic

operation

of

the

instrument.

Preliminary Setup. Install

the

7A

15A/7

A15AN

into

any

·1000-series oscilloscope vertical

compartment

and

set

the

oscilloscope

VERTICAL

MODE and

TRIGGER

SOURCE

to

the

proper

settings.

Install a 7-series time-base

unit

into

a

horizontal

compartment

and

set

the

oscilloscope

HORIZONTAL

MODE

to

~he

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

7A15A/7A15AN

AC-GND-DC switch

to

GND and

position

the

trace

to

the

center

of

the

graticule.

2.

Set

the

VOL

TS/DIV

switch

to

10 mV and apply a

40

mV 1 kHz square-wave signal from

the

oscilloscope CALI-

BRATOR

to

the

7A15A/7A15AN

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.

5.

Set

the

oscilloscope

CALIBRATOR

to

4 mV and

the

7A15A/7A15AN

MAG switch

to

X10.

Check

for a four-

division display.

6.

(7A15A

Only) Press

the

7A15A

IDENTIFY

button,

check

that

the

display moves

upward

approximately

0.3

division

and

the

readout

(if so

equipped)

reads

"IDENTIFY".

GENERAL

OPERATING

INFORMATION

Signal Connections

In general,

probes

offer

the

most

convenient

means

of

connecting

a signal

to

the

input

of

the

7A15A/7A15AN.

A

10X

attenuator

probe

offers a high

impedance

and allows

2-2

I

the

circuit

under

test

to

perform

very close

to

normal I

operating

conditions.

•

The

Tektronix

P6053

probe

is

equipped

with

a

readout

I

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

15A

and an oscilloscope

equipped

with

readout.

The

Tektronix

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

I

nco

catalog.

Vertical Gain Check

and

Adjustment

To

check

the

gain

of

the

7A15A/7A15AN,

set

the

VOLTS/DIV

switch

to

10

mV and

connect

a

40

mV,

1 kHz

signal

from

the

oscilloscope

calibrator

to

the

Input

connec-

tor.

The

vertical

deflection

should

be

exactly

four

divisions.

If

not,

adjust

the

front

panel GAIN

for

exactly

four

divi-

sions.

Input

Coupling

The

AC-GND-DC switch allows a

choice

of

input

coup-

ling

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

applica-

tions.

For

AC signals with frequencies below

about

30

Hz

(10Hz

with

a 10X

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

combination

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

coupl

ing

capacitor

to charge,

set

the

coupling

switch

to

AC.

I

The GND

position

provides a

ground

reference

at

the

I

input

of

the

amplifier

without

externally

grounding

the

Input

connectors.

However,

the

signal

connected

to

the.

input

is

not

grounded,

and

the

same

DC

load

is

presented

I

to

the

signal

source.

REV.

S, OCT. 1974 I

I

I.

I

VOLTS/DIV,

VARIABLE

and MAG Controls

The

amount

of

deflection

produced

by a signal

is

deter-

mined

by

the

signal

amplitude,

the

attenuation

factor

of

the

probe,

the

setting

of

the

VOL

TS/DIV

switch,

the

setting

of

the

VARIABLE

Control,

and

the

setting

of

the

MAG

switch.

Calibrated

deflection

factors

represented

by

the

setting

of

the

VO L

TS/D

IV

switch

apply

only

when

the

VARIABLE

control

is

in

the

CAL

position

(fully clock-

wise)

and

when

the

MAG switch

is

set

to

Xl.

I

The

VARIABLE

control

provides variable

uncalibrated

settings

between

the

calibrated

s,teps

of

the

VOL

TS/D

IV

switch.

With

the

VARIABLE

control

set

fully

counter-

clockwise

and

the

VOL

TS/DIV

switch

set

to

5 volts/div,

the

uncalibrated

deflection

factor

is

extended

to

at

least

2.5

times

the

attenuator

setting. By applying a

calibrated

voltage source

to

the

Input

connector,

any

specific deflec-

tion

factor

can be

set

within

the

range

of

the

VARIABLE

control.

The

MAG switch increases

the

VOLTS/DIV

switch

sensitivity

by

a

factor

of

10

when

in

the

Xl0

position.

Thus,

with

the

MAG switch

set

to

Xl

0 and

the

VO L

TS/

[)

IV switch

set

to

5 mV

/d

iv,

the

deflection

factor

is

extended

to

500}J..V/div.

The

MAG switch also

effects

a

circuit

in

the

7A

15A

which

corrects

the

readout.

With

the

MAG switch

set

to

X10,

the

bandwidth

of

the

amplifier

is

reduced.

Refer

to

specifications

in

Section

1.

Polarity Switch

I.

The

POLAR ITY

switch

provides a

means

of

inve~ting

the

displayed signal. With

the

POLAR ITY

set

to

+ui'

a

positive-going signal

at

the

INPUT

produces

an

up

ard

I

deflection

of

the

CRT

display. With

the

POLAR ITY s t

to

INVERT,

a positive-going signal will

produce

a downvVard

deflection

of

the

CRT

display. !

Trace Identification

(7A15A

only)

I

When

the

IDENTIFY

button

is

pressed,

the

tract'

is

deflected

.upward

about

0.3

division

to

identify

the

7A

5A

trace. ThiS

feature

IS

particularly

useful

when

mul iple

traces are

displayed

on

the

CRT.

In

mainframes

with

rfad-

out,

It

also replaces

the

deflection

factor

readout

with

i

the

lIVord

"IDENTIFY".

i

I

When using a 100X

readout

coded

probe

such as a

P~09

(Tektronix

Part No.

010-0264-01),

the

7A

15A

encodin

of

CRT

readout

is

incorrect

for

a

number

of

VOL

TS/

IV

settings. These

incorrect

readings

occur

with

the

AG

switch

in

the

1X gain

position

as follows:

Actual:

50

V,

10V,

20V

and

lS,

should

read:

500mV,

100V,

200V

land

lkV.

If

a

100X

probe

is

to

be used

with

the

7A154.

at

these sensitivities, in a

CRT

readout

mainframe,

it migh be

preferable

to

defeat

the

probe

coding

and

multiply

the

plug-in

VOL

TS/DIV

by a

factor

of

100

as

in

non-c

ded

operation.

Possible means

for

achieving

this

is;

use a P6

09

I

Tektronix

Part No.

010-0170-00

(no

readout

connect

r),

defeat

the

probe

coding

connection

in

the

7A

15A

by dis-

•

connecting

R48,

defeat

the

CRT

readout

entirely

for

the

7A

15A

by unsoldering

the

A37

and

837

cable

connections

I

between

the

readout

EC

board

and

the

mainframe

EC

board.

I

REV.

B, OCT.

1974

Operati

ng I

nstructions-7

A

15A/7

A

15AN

APPLICATIONS

General

The

following

information

describes

the

procedures

and

techniques

for

making

measurements

with

a 7A

15A/

7A

15AN

and

the

associated

Tektronix

oscilloscope

and

time-base.

These

applications

are

not

described

in

detail,

since each

application

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

Tektronix

Field

Office

or

representative

for

assistance

in

making specific measure-

ments

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.

2.

Set

the

Coupling

switch

to

AC.

NOTE

For low-frequency signals

below

about

30

hertz, use

the

DC

position to prevent attenuation

of

the signal.

3.

Set

the

VOLTS/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

wh ich displays

several cycles

of

the

waveform.

5.

Turn

the

7A15A/7A15AN

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

thl~

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

them

peak to peak.

7. Multiply

the

distance

measured

in

step

7

by

the

VO L

TS/D

IV

switch

setting.

I

nclude

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

VOL

TS/DIV

switch

is

set

to

1 V.

2-3

Operating

Instructions-7

A

15A/7

A

15AN

Vertical

deflection

___

L

'r-7

1/

Position

to

center

vertical

line

\ \ r\

'r---

--

-)

1\

\ !

.,

II

~

/

\

lJ

~

.\

1\

\

Jr"\

I \

II

~

J

j

fig.

2-1. Measuring

the

Peak-to-Peak voltage

of

a waveform.

Volts

vertical

VOL

TS/DIV

X

deflection

X

setting

(divisions)

Substituting

the

given values:

Volts

Peak

to

Peak

=

4.5

X 1 X

10

The

peak··to-peak voltage

is

45

volts.

probe

attenuator

factor

If

you

are using a 7A

15A

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.

Instantaneous Voltage Measurements (DC)

To

measure

the

DC level

at

a given

point

on

a

waveform,

proceed

as

follows:

1.

Connect

the

signal

to

the

I

nput

connector.

2.

Set

the

VOL

TS/DIV

switch

to

display

about

five divi·

s.ions.

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.

:2-4

NOTE

To

measure a voltage level with respect to another

voltage rather than ground, make the following

changes to Step 3.

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

reference

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

VO L

TS/D

IV

switch

setting.

I

nclude

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

10X

probe

with

a

VOL

TS/DIV

switch

setting

of

0.5

V.

Using

the

formula:

Instan-

taneous

=

Voltage

vertical

VOL

TS/

probe

distance

X

polarity

X DIV X

attenuation

(divisions)

setting

factor

Substituting

the

given values:

Instantaneous

Voltage

=

4.6

X 1 X

0.5

V X

10

The

instantaneous

voltage

is

23

volts.

REV.

B, OCT.

1974

I

.1

I

·1

I

I.

I

I·

I

Point

A

tI'

/

V

r

--r--

Vertical

--

-

..

~

distance

J

____

\

Reference

line

I'ig.

2·2

Measuring

instantaneous

voltage

with

respect

to

some

reference.

Comparison Measurements

In some applications

it

may

be

desirable

to

establish

units

of

measurement

other

than those indicated

by

the

VOL

TS/D

IV

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

divi-

sions

of

deflection.

The

following

procedure describes

how

to

establish

arbitrary

units

of

measure

for

comparison

measurements.

To

establ

ish

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

VAR

IABLE

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

establ

ish

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

REV.

B,

OCT.

1974

Operating I

nstructions-7

A

15A/7

A15AN

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) estab-

lished in step 2 and the setting

of

the

VOLTS/DIV

switch.

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 calcu-

late the

amplitude

of

the

unknown

signal using the

following

formula:

Signal

Amplitude

VOLTS/DIV

X

setting

vertical

conversion

factor

vertical

X deflection

(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/D

IV

setting

of

2

V,

the peak

to

peak

amplitude

of

an

unknown

signal

which

produces a vertical

deflection

of

five divisions

can

be

deterrnined

by

using the

signal

amplitude

form

ula (step 6):

Signal

Amplitude

2V

X 1.5 X 5 15 volts

2-5

I

NOTES

e-

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

I

--------------------.

I

.---------------------

I

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

I

------------------------el

I

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

I

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

I

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

I

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

I

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

I

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

I

------------------------e.

I

I.

I

I.

I

7A15A/7A15AN

SECTION

3

CIRCUIT

DESCRIPTION

Introduc:tion

This

section

of

the

manual

contains

a

description

of

the

circuitry

used

in

the

7A15A/7A15AN

amplifier.

The

description

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

following discussion

is

provided

to

aid

in

under-

standing

the

overall

concept

of

the

7A

15A/7

A15AN

before

the

individual

circuits

are discussed in

detail.

Only

the

basic

interconnections

between

the

individual

blocks

are

shown

on

the

block

diagram (see Diagrams

section).

Each

block

represents a

major

circuit

within

the

instrument.

The

si~lnal

to

be

displayed

on

the

CRT

is

applied

to

the

Input

connector.

The

signal passes

through

the

input

coupling

switch,

where

the

appropriate

coupling

is

selected,

to

the

aHenuators.

The

VO L

TS/D

IV

switch

selects

the

correct

amount

of

attenuation

and

the

signal

is

passed

to

the

Input

Amplifier.

The

I

nput

Amplifier

provides signal

polarity

inversion

in

addition

to

gain

setting,

variable gain

control,

and

trace

positioning.

The

output

of

this

circuit

is

applied push-pull

to

the

Signal

and

Trigger Amplifiers.

The

signal and trigger

outputs

are provided

to

the

oscilloscope via

the

Interface

connector.

The

Readout

encoding

circuit

(7A15A

only)

provides

readout

logic

for

the

oscilloscope

readout

system.

Logic

is

supplied

identifying

the

polarity,

deflection

factor,

and

the

!REV. B, OCT.

1974

uncalibrated

symbol

(when

the

VAR lAB

LE

knob

is

not

fully

clockwise).

When

the

IDENTIFY

button

is

pressed,

the

trace

is

deflected

about

0.3

division

and

the

deflection

factor

readout

is

replaced

by

the

word

"IDENTIFY"

(7A15Aonly).

DETAILED

CIRCUIT

DESCRIPTION

Attenuator

General

The

Attenuator

circuit

determines

the

input

coupling

and

the

deflection

factor.

A diagram

of

this

circuit

is

shown

on

Diagram 1

in

the

Diagrams

section.

AC-GND-DC Switch

I

nput

signals

connected

to

the

I

nput

connector

can be

AC-coupled,

DC-coupled, or

internally

disconnected.

S100A

is

a

cam-type

switch;

a

contact-closure

chart

show-

ing

the

operation

is

given

on

Diagram

1.

The

dots

on

this

chart

indicate

when

the

associated

contacts

are

in

the

position

shown

(open

or

closed). When

the

AC-GND-DC

switch

is

in

the

DC

position,

the

input

signal

is

coupled

directly

to

the

Input

Attenuator

stage.

In

the

AC

position,

th

e

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

Rl02,

connected

across

the

AC-GND-DC

switch,

allows

Cl0

to

be

pre-charged

in

the

GND

position

so

the

trace

remains

on

screen

when

switching

to

the

AC

position

if

the

applied signal has a high DC level.

Input Attenuator

The

effective

overall

deflection

factor

of

the

7A

15A/

7A15AN

is

determined

by

the

setting

of

the

VOLTS/DIV

switch,

S100B.

The

basic

deflection

factor

is

five millivolts

per

division

of

CRT

deflection

(with Mag switch

set

to

Xl).

To

increase

the

basic

deflection

factor

to

the

values indica-

ted

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

position,

input

attenuation

is

not

used;

the

input

signal

is

connected

directly

to

the

input

amplifier.

3-1

Circuit

Description-7A15A/7A15AN

For

switch positions above five millivolts,

the

attenua-

tors are switched

into

the

circuit singly

or

in

pain

to

pro-

duce

the

deflection factor indicated on

the

frort

panel.

These

hybrid

attenuators

are frequency-compensated

voltage dividers.

For

DC

and low-frequency signals,

the

attenuators

are primarily resistance dividers and

thH

voltage

attenuation

is

determined by

the

resistance ratio

in

the

circuit. The reactance

of

the

capacitors

in

the

c:ircuit

is

so

high

at

low frequencies

that

their

effect

is

negligible. How-

ever,

at

higher frequencies,

the

reactance

of

the

c,lpacitors

decreases and

the

attenuator

becomes primarily

il

capaci-

tance divider.

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) for each setting

of

the

VOLTS/D

IV

switch. Each

attenuator

c:ontains an

adjustable series capacitor

to

provide

correct

attenuation

at

high frequencies, and an adjustable

shunt

capacito'

to

pro-

vide

correct

input

capacitance.

I

nput

Amplifier

General

The

Input

Amplifier converts

the

single-ended signal

applied

to

the

Input

connector

to

a differential (push-pull)

output.

A schematic of this circuit

is

shown on D agram 2

in

the

Diagrams section.

Input

Source Follower

The

Input

Source Follower

0210A

provides a high

input

impedance with a low impedance drive for

the

following

stage. R210 limits

the

current

drive

to

the

gate of

0210A.

Dual-diode

CR210

provides circuit protection by limiting

the

voltage swing

at

the

gate

of

021

OA

to

about

± (positive

or

negative) 15 volts.

021

DB

provides a

constant

current

source for

0210A.

0210A

and

0210B

are encaps'Jlated

in

the

same case so

that

0210B

temperature

compensates

the

circuit.

Amplifier

The signal from

the

Input

Source Follower

is

applied

to

paraphase amplifier

0220-0320.

The

paraphase amplifier

converts

the

single-ended

input

to

a differential (push-pull)

output.

It also provides a means

of

compensating for stray

currents

throughout

the

entire amplifier by varying

the

DC

Level

at

the

base

of

0320

via

the

DC

Bal

control R322.

The

differential signal from

the

paraphase amplifier

is

cascoded

to

the

Inverting Amplifier, a set

of

common

base differen-

tial amplifiers

0230-0330

and

0235-0335.

With

the

POLARITY switch set

to

+UP,

0230

and

0330

am forward

biased while

0235

and

0335

are reverse biased.

The

signal

is

therefore

allowed

to

pass un-inverted through

0230-0330.

By

setting

the

POLARITY switch

to

INVERT,

3-2

I

0230

and

0330

are reverse biased and

0235

and

0335

are I

forward biased.

The

signal

is

inverted through

0235-033~

.•

Current

gain for amplifiers

0230-0330

and

0235-0335

IS

controlled

by

the

GAIN

potentiometer

R238 and I

VARIABLE

control

R239.

The

output

from

0230-0330

or

0235-0335

(depending on

the

POLAR ITY switch)

is

connlected

to

the

Xl

amplifier,

0240-0.340,

and

the

Xl0

amplifier,

0245-0345.

The

MAG

switch determines which I

amplifier

(Xl

or

Xl0)

is

on,

by switching their

emitter

suppl:y voltages.

Current

gain for

the

Xl

0 amplifier

is

adjusted by R245. R341 and C341 provide frequency com-

pensation for

the

Xl

amplifier. The signal from

the

Xl

or I

Xl0

amplifier (depending on

the

MAG

switch)

is

cascoded

through

the

common

base amplifier,

Q250-0350,

to

the

Signal

Amplifier,

0260-0360,

and Trigger Amplifier, I

0270-0370.

Connectors and Readout

General I

The

Connectors and

Readout

circuit consists

of

the

power supply and signal distribution from

the

Interface I

Connector

and

the

Readout

Encoding circuit. A schematic

of

this circuit

is

shown on Diagram

~I

in

the

Diagrams

section.

Connectors

All

the

connections made

to

the mainframe by

the

7A1fiA/7A15AN are shown on

the

Connectors portion of

Diagram 1. Also shown are

the

power supply decoupling

components.

Readout Encoding

(7A15A

only)

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

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

uncal 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

POLAR ITY switch

is

in

the

INVERT position.

This results

in

the

symbol t (inverted) being displayed

precl~ding

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 3) indicate

when

the

associated

contacts

on

the

VO

LTS/D IV cam

®

I

.-

I

I.

I

I.

I

switch are closed.

R633,

R634,

and

R635

select

the

number

1,

2,

or

5

depending

on

the

combination

that

is

switched in. R637 selects

the

m (milli-) prefix and

R639

selects

the

symbol V (volts)

in

the

5 mV

through

.5 V

(500

mY) positions

of

the

VOL

TS/DIV

switch.

R638

selects

the

symbol V

in

the

1,

2,

and 5 V positions.

R630,

R631,

and

the

output

of

the

probe

sensing stage

(0620)

select

the

decimal

point

(number

of

zeroes), again dependin!1 on

the

resistor

combination

switched

in

by

the

VOLTS/D

IV

switch.

Probe sensing stage

0620

identifies

the

attenuation

factor

of

the

probe

connected

to

the

Input

conne,ctor 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

I

nput

connector

provides

the

input

to

the

probE sensing

device from

the

probe

coding resistance (coded probes

only; see Operating Instructions).

The

third

contact

is

also

used for

the

IDENTIFY

input.

The

coding resistor forms a

voltage divider with R621 through CR621

to

the

-15

V

supply.

The

resultant

voltage sets

the

bias on 01320

and

determ

ines

the

collector

current,

along with emitter resistor

R622.

When

the

-15

volt time-slot pulse

is

applied to Inter-

face

Connector

833,

0620

is

interrogated and its

collector

current

is

added

to

the

column

current

output

through

Interface

Connector

A37.

REV.

B,

OCT. 1974

Circuit Description--7A

15A/7

A

15AN

With a 1X

probe

(or

no

probe)

connected

to

the

Input

connector,

0620

is

turned

off.

The

deflection

factor

read-

out

is

determined

by

the

VOLTS/DIV switch position. With

a

10X

probe

connected,

the

bias

on

Q620

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

th

ings

when

pressed:

1. It causes

the

trace representing

the

appropriate

channel

of

the

7A

15A

to

move.

2. Forward biases CR621 and

0620

to

result in a

sufficient

amount

of

collector

current

which,

when

added

to

the

column

current

output

replaces

the

deflection

factor

readout

with

the

word

"IDENTIFY".

These

two

actions

aid

in

identifying

the

7A

15A

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

I

NOTES

.'

I

.1

I

.,

I

7A15A/7A15AN

I.

I

SECTION

4

MAINTENANCE

I

Introduction

This

section

of

the

manual contains maintenance

infor-

mation

for

use

in preventive maintenance, corrective main-

tenance, and

troubleshooting

of

the 7A

15A/7

A

15AN.

Further

maintenance

information

relating

to

general

maintenance can

be

found

in the

instruction

manlJals

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

I.

semiconductor

devices used in the

unit

are

not

recom-

mended

as

a preventive maintenance measure.

See

sem

iconductor-checking

information

given

under

1 rouble-

I

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 Poly-

phenylene 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

I •

dirt

can

be

removed

with

a

soft,

dry

brush,

cottor-tipped

swab, or

cloth

dampened

with

a

mild

detergent and

water

I solution.

I

REV.

B,

OCT.

1974

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

con-

taining

the necessary

lubricating

materials and

instructions

is

available

through

any

Tektronix

Field

Office.

Order

Tektronix

Part

Number

003-0342-01.

TROUBL

ESHOOTING

General

The

following

is

provided

to

augment

information

contained in

other

sections

of

this

manual when

trouble-

shooting the

7A

15A/7A

15AN.

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. Circu

it

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.

I

mportant

voltages are also shown.

Circuit

Boards_

The

circuit

boards used in the 7A

15A/

7A

15AN

are

outlined

on the schematic diagrams, and

photographs

of

the

boards

are

shown on the backs

of

the

schematic diagrams. Each

board-mounted

electrical com-

ponent

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

EIA

standard

color

code.

Components

not

color

coded usually have the value

printed

on

the

body.

The

insulated wires

used

for

interconnection

in the

7A

15A/7

A

15AN,

are

color

coded

to

facil

itate

tracing wires

from

one

point

to

another

in

the

unit.

Semiconductor

Lead Configuration_ Fig.

4-1

shows the

lead

configurations

of

the

semiconductor

devices

used

in

this

instrument.

4-1

Maintenance-7

A

15A/7

A15AN

C m

E C E C E

B B B

Plastic Case

Transistors

o

S G

Dual-FET

a

~\-

common

anode/

\

cathode

clip

off

Dual-Diode

Fig. 4-1. Electrode configuration

for

semiconductors

in

the

7A

15AI

7A15AN.

Troubleshooting Equipment

The following

equipment

is

useful for troubleshooting

the

7A15A/7A15AN.

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

Tektronix

Type

576

will give

the

most

complete information.

2.

DC

Voltmeter

and

Ohmmeter-A.

voltmeter

is

required for checking voltages within the !Circuits, and an

ohmmeter

for checking resistors and diodes.

3.

Test Oscilloscope-A.

test

oscilloscop1e

is

required

to

view waveforms

at

different points

in

the

circuit. A

Tektronix

7000-series Oscilloscope equipped with a

readout

system, 7D13 Digital Multimeter unit, 7B-series Time-Base

unit, and a 7A-series Amplifier

unit

with a

lOX

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.

4-2

Troubleshooting Procedure

This troubleshooting procedure

is

arranged

in

an order

which checks

the

simple

trouble

possibilities before

proceeding with extensive troubleshooting.

1. Check Control Settings. An incorrect setting

of

the

7A

15A/7

A15AN controls can ind icate a trouble

that

does

not

exist.

If

there

is

any question

about

the

correct

func-

tion

or

operation of a

control

or front-panel

connector,

see

the

Operating Instructions section.

2. Check Associated Equipment. Before proceeding

with troubleshooting

of

the

7A15A/7A15AN, 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.

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

Part

II

of

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; how-

ever, 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

Diagrams section.

6.

Check

Individual Components.

The

following

methods are provided for checking

the

individual com-

ponents

in

the

7A

15A/7

A15AN.

Components

which are

soldered

in

place are best checked by disconnecting one end

to

isolate

the

measurement

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

dichlorodi-fluorremethane (Freon 12,

Dupont

or

Can-

a-Gas) may also be

used.

Other types

of

circuit

coolant

may

damage

the polyphenylene oxide boards.

®

I

.'

I

.,

I

I 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

I .checked by

substituting

a

component

known

to

be

good;

however, be

su

re

that

circuit

conditions

are

not

such

that

a

replacement

might

also be damaged. If

substitute

transistors

I

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 condi-

tions, some

defects

may go

unnoticed.

Fig.

4-1

shows base

pin and

socket

arrangements

of

sem

iconductor

devices.

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

that

has

a high internal

current. High currents

may

damage the diodes.

I.

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.

I

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

110t

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. Recalilbration

of

the

affected

circuit

may be necessary.

CORRECTIVE

MAINTENANCE

I General

• Corrective

maintenance

consists

of

component

replace-

I

ment

and

instrument

repair. Special techniques required

to

replace

components

in

this

instrument

are given here.

I REV.

C,

MAR.

1975

Maintenance-7

A15A17A

15AN

Obtai·ning Replacement Parts

Standard

Parts. All electrical

and

mechanical

part

replacements

for

the

7A15A17A15AN can be

obtained

through

your

local

Tektronix

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 replace-

ment

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 com-

ponent

may

affect

the performance

of

the instru-

ment,

particularly

at

high frequencies.

All

replace-

ment

parts should be

direct

replacements unless

it

is

known

that

a

different

component

will

not

adversely

affect

instrumentperformance.

Special Parts.

In

addition

to

the

standard

electronic

components,

some

special parts are used in

the

7A15A/

7A15AN. 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.

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. I

nstrument

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

thf1

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:

4-3

Tektronix 7a15a User manual

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