Tektronix 555/22a User manual

INSTRUCTION

IVIANUAL

Serial

Number

__

___

_

Tektronix,

Inc.

S.W. Millikan

Way

e

P.

0.

Box

500

•

Beaverton,

Oregon

97005

•

Phone

644-0161 •

Cables:

Tektronix

070-403

464

ii

ktronix

repair

and

replacement-part

·

;;·;

§ll!lif'VJ~a

is

geared

directly

to

the

field., there-

all requestS for repairs

and

replace-

pad

should

be

directed to

the

Tek-

ix

Field

Ofti

or.

Representative

in

your

. This procedure

Witl

as.s

_ure you

the

possible service.. Please inc

-illililrnrn•nt Type

and

Serial number with

p,'t_-.:,·

t:•ioJUtJSTs for

parts

or service.

and

price

I

T.

0.

33Al-1.3-152-ll

18 SeptEmber 1968

IDENTIFYING

TECHNICAL

ORDER

This

ITO

replaces

ITO 33Al-1.3-152-ll, dated 1

July'

1968, and

the

cODRercialaanual.

1.

PURPOSE~

This

technical

order

is

issued

for

the

purpo'e

of

identifying

and

authorizing

for

official

use a commercial

publication

identified

as

follows'

CONTRACTOR---

Tektronix

ClMMERCIAL

NUMBER--- TJpe 555/2ll/22A

..

TITLE---

Instructions

with

Parts

Breakdown

-Oscilloscope

DATE---

Hot

dated.

ADDITIONAL

IDENTIFICATION:

2.

FILE

LOCATION.

The

above

listed

commercial

publication

is

filed

in

3.

SUPPL~ENTARY

INFORMATION.

The

information contained

in

the

above

listed

commercial

publication

is

supplemented

as

follows

for

official

use.

Marma1

Chaage

...

Modification

Insert,

Type

555,

Mod

101D,

Copyright

1966

Reference Page

1-1,

Table

1-1:

Delete

the

risetime

of

11

14.5

nsec" and add "16 nsec

11

tor

the

'l';ype

lAl

plug-in

over

the

calibrated

defiection

!actor

0.005

to

0.05

v/c:ra.

Delete

the

passband "de

to

24

•c"

and add •de

to

23

ac."

Delete

the

riset:ime

or

11

23

nsec" and add

"24

nsec"

tor

the

Type

H

plug-in.

PUBLISHED

UNDER

AUTHORITY

OF

THE

SOCRETARY

OF

THE

AIR

FORCE

This

technical

order

issued

by

SAAMA

(SANST)

NOTICE:

Reproduction

for

nonmilitary

use

cf

the

information

or

illustrations

contained

in

this

publication

is

not

permitted without

specific

approval

of

the

issuing

service.

AF,

Nunna &

Hhnler,

Inc

..

,

C1nc1nnat1,

Ob1o4oo, 11-68 "LIBRARIAN: CHECK FOLD-OUT PAGE FILING SEQUENCE"

iv

Type

555/21A/22A

SECTION J

CHARACTERISTICS

NOTE

The following

characteristics

are

for

the

Tektronix

Type

555

Oscilloscope

(5/N's

7000

and

above)

with

Type

21

A

and

Type

22A

Time

Base

units.

GENERAL

INFORMATION

The Type 555 Oscilloscope

is

a

wide-range

dual

-

beam

laboratory-type

instrument providing

accurate

voltage

and

time measurements

in

the

de

to

30

Me frequency

range.

Two

complete

horizontal

and

vertical deflection systems per-

mit completely

independent

operation

of

the

two

beams.

Either

of

the

two

time-base

plug-in units

can

control the

sweep

of

either

or

both

of

the

beams

. The

two

vertical chan-

nels utilize

separate

plug-in preamplifier units, allowing you

to

select the

bandpass,

risetime,

type

of input

and

sensitivity

required

for your

application.

Special circuit;

incorporated

in

the system provide selection

of

an

accurate,

continuously-variable

delay

in

the presenta-

tion of

one

of the sweeps. The

sweep

may

be

delayed

from

.

05

microseconds to 50 seconds after

application

of a trig-

gering

pulse. This feature permits you to

expand

a selected

portion of the

delayed

sweep,

thereby

providing precise time

measurements

and

detailed

observation of the signal.

Both

the

delayed

and

the

undelayed

sweeps

are

presented

on the

oscilloscope screen.

VERTICAL

DEFLECTION

SYSTEM

Characteristics for both vertical channels of the oscillo-

scope

are

identical. The

actual

specifications

depend

pri-

marily on the vertical plug-

in

units used with the Type 555.

See

Table

1-1 for the vertical characteristics

of

the system

when using various plug-in units.

TABLE

1-1

Vertical

Characteristics

with

Specific

Plug-In Units*

PLUG-IN

TYPE

.

CALIBRATED

PASSBAND

RISETIME

INPUT

DEFLECTION

FACTOR CAPACITANCE

TYPE

B 5

mv/cm

to

0.05

v/cm

2 cps to 12

me

30 nsec

Wide-Band

47

pf

High-Gain 0.05

v/cm

to

20

v/cm

de to 20

me

18 nsec

TYPE

CA

Dual-

Trace

0.05

v/cm

to 20

v/cm

de to 24

me

15 nsec 20 pf

DC

TYPE

1A1

0.005

to

0.05 v

/em

de to

23

me

16 nsec

Wide-Band

15 pf

Dual-Trace 0.05

to

20 v/ em

de

to 33

me

11

nsec

TYPE

D

High-

Gain

1

mv/cm

to

50

v/cm

de

to 2

me

0.18

11-sec

47

pf

DC

Differential

TYPE

E

low-level

50

11-v/cm

to

10

mv/cm

0.06 cps to 60

kc

6

11-sec

50 pf

AC

Differential

TYPE

G

Wide-Band

0.05

v/cm

to

20 v/ cm de to 20

me

18 nsec

47

pf

DC

Differential

TYPE

H

Wide-Band

0.005

v/cm

to

20

v/cm

de to 15

me

24 nsec

47

pf

High-Gain

TYPE

K

Fast-Rise 0.05 v

/em

to

20 v

/em

de to 30

me

12 nsec 20 pf

DC

TYPE

L 5

mv/cm

to

2

v/cm

3 cps

to

24

me

15 nsec

Fast-Rise 20 pf

High-Gain 0.05 v

/em

to

20 v

/em

de

to

30

me

12 nsec

TYPE

M

Four

Trace

0.02

v/cm

to

10

v/cm

de to 20

me

18 nsec

47

pf

DC

•Data

on

special-purpose

vertical plug-Ins given

at

the

end

of

this section.

®!

1-1

Characteristics-

Type

555/21A/22A

HORIZONTAL

DEFLECTION

SYSTEM

Sweep

Rates

From

0.1 microsecond to 5 seconds

per

centimeter

in

24

calibrated steps.

An

uncalibrated control provides variable

control of sweep rates between the calibrated steps,

and

ex-

tends slow sweep

range

to

about

12 seconds per centimeter.

Accuracy of calibrated sweep rates

is

within 3% (typically

1

%1

with magnifier off.

Magnifiers

Provide horizontal

5X

magnification

of

the center 2-centi-

meter portion of the unmagnified crt display when the inter-

nal time

base

generators provide the horizontal deflection.

Extend the fastest sweep rate of either beam to 0.

02

micro-

second

per

centimeter. Sweep rates

ore

accurate to within

5% with magnifiers on.

External Horizontal Inputs

Rear-panel connectors permit application of external hori-

zontal signals.

Deflection Foetor-Continuously variable from

approxi

-

mately 0.2 volts per centimeter to approximately 20 volts

per centimeter.

Passband-De

to approximately 350

kc

(3

db

down)

at

maximum gain.

Input Impedance -Approximately 1 megohm resistance

with

47

pf parallel capacitance with the

HORIZ

.

DISPlAY

switch set

at

EXT

. A

TTEN

.

X1.

Sweep

Modes

Type

21

A

in

Time Base A compartment-Normal, auto-

matic baseline,

and

single sweep.

Type 22A

in

Time Bose B compartment-Normal,

auto

-

matic baseline, single sweep, sweeps once for each 'A' de-

layed trigger,

and

triggerable once for each 'A'

delayed

tr

igger.

Automatic baseline mode operates only on signals with

repetition rates

above

20

cps. Below

20

cps one of the

other sweep modes must be used.

Triggering Signal Sources

Upper beam or lower beam vertical amplifiers, external

signals or power line signals; upper beam or lower beam

plug-in units when using multi-trace vertical plug-

in

un

its with

single-channel trigger pickoff.

Trigger Slope

and

Coupling

Positive

(+)

or negative (- ) slope, oc-or de-coupled.

1-2

Triggering

Signal

Requirements

15/N

11000-upl

Internal-Signals producing a

mm1mum

of 0.2 centimeter

of vertical deflection (

+

AC

only) up to 1

kc,

or

2 centi-

meters of deflection (+

AC)

up to 30

me.

External-Signals with minimum

of

0.5 volt

peak

to

peak

(+

AC

and

+

DC)

up to 1

kc,

or

0.6

volt(

+

AC

only) up

to 30

me

.

(The

triggering lEVEl control has

range

of + 10 volts

and

the

VERNIER

control has a

range

of

+ 1 volt, making the

overall

range

+ 10.1 volts. The instrument

will

trigger on

signals larger than + 10.1 volts, but the lEVEl

and

VERNIER

control

will

not

be

completely effective

in

determining the

triggering level.)

15/N

7000-109991

Internal-Signals producing a minimum

of

0.2 centimeters

of

vertical deflection, up

to

5 me,

or

1 centimeter

of

deflec-

tion up to 30

me.

External-Signals

with minimum

of

0.2 volts peak-to-peak

up

to

10

me,

or

0.5 volts up

to

30

me.

(The

instrument will trigger on signals

greater

than 10

volts, but the lEVEl control

is

effective

over

a

range

of

+ 10

volts. The

VERNIER

control

operates

over a + 1-volt

range

.)

Delayed

Sweep

Delay-0

.1 microsecond

to

50 seconds, continuous-

ly

variable.

Incremental

Accuracy-Within

0.2%, between

the

1.00

and

10.00 positions of the

DElAYED

TRIGGER

control, on

any

single setting

of

the TIME/CM switch.

Overall Accuracy-Within

3%

of

the indicated value.

Time Jitter-less

than

1

part

in

20,000.

CATHODE

RAY

TUBE

(crt)

Type

T5550-2-1 (internal graticule).*

Phosphor

Type

P2

normally supplied; types

P1,

P7

and

P11

optional;

other types

available

on special

order

.

Accelerating Potential

10,000 volts.

Useable

Viewing

Area

6 by 10 centimeters. The 6-centimeter vertical dimension

consists of 4 centimeters for

each

beam

with 2 centimeters

common to both beams.

Trace

Alignment

Traces

are

parallel to

each

other

within 0.1 major division

per 10 major horizontal divisions, when the traces

are

cen-

tered vertically

and

there

is

no input signal.

•Crt

type

is

T5550-2

(external

graticule)

for instruments with

SIN

's

7000

-

8999

.

@

Internal Unblanking

Intensity-type,

de

-

coupled.

External Intensity Modulation (Z-axis)

Coupling-Input

signals

ac

-

coupled

to crt control grids

through

rear

-

panel

connectors.

Input Time Constant-Typically

about

10 milliseconds with

low external

impedance

.

Input

Amplitude-Typ

ically a 20-volt peak-to-peak signal

will

produce

normal intensity modulation.

Multi

Trace Chopped Blanking

Crt circuit permits vertical plug-in units with multi-

trace

blanking to tum off

the

display

while switching

between

input

channels.

Internal Graticule

Markings--6

vertical

and

10

horizontal 1-centimeter (major)

divisions; 2-millimeter markings (minor divisions) on

the

verti-

cal centerline

and

on

the

upper

beam

and

lower

beam

hori-

zontal centerlines 2 centimeters from the

top

and

bottom of

the graticule.

Illumination-Variable

edge

lighting.

AMPLITUDE CALl

BRA

TOR

Output Waveform

Square

-

wave

signal

at

approximately

1,000 cps.

Output

Voltage

0.2 millivolts to 100 volts

peak-to-peak

in

18 steps.

Accuracy

Peak-to-peak

amplitude

within

3%

of

indi

cated

voltage

with

load

impedance

above

1 kilohm.

INSTRUMENT POWER

Internal Power Supplies

Electronically

regulated

circuits for

stable

operation

on

power line voltages from 105 volts to 125 volts when wired

for 117-volt

operation

; from 210 volts to 250 volts when

wired for 234-volt operation.

Line

Voltage

The line

voltage

for which

the

instrument is wired

is

indi-

cated

on

a metal

tag

on

the

rear

panel

of

the

power

supply

unit.

Changes

can

be

made

in

the

internal wiring to permit

operation

on

design-center voltages

of

117 or 234 volts,

as

indicated on

the

Decoupling Network schematic

diagram

.

Wiring

changes

for the

power

transformers, s

aturable

reactor

and

fans

are

all shown on

the

diagram

.

Characteristics-

Type

555/21A/22A

Line

Fuses (located on the front panel

of

the

power

supply

un

i

t)

ore 7

amp

slow-blowing for the

AC

Heater$

and

5

amp

slow-blowing for the

DC

Supplies for 117-volt

operat

ion; 4

amp

slow-blowing for the

AC

Heaters

and

3

amp

slow-blow-

ing for the

DC

Supplies for 234-volt operation.

Line Frequency

50 cps to 60 cps.

Power Consumption

Maximum of

about

1050

watts

including plug-in power

consumption.

OTHER

CHARACTERISTICS

Output Signals

Available

Calibrotor- 1 kilocycle (approx.)

square

wave

,

at

ampli-

tudes from 0.2 millivolts to 100 volts.

Delayed

Trigger

Pulse-Differentiated

positive-going pulses

approximately

5 volts

in

amplitude

, occurring

at

the

end

of

the

delay

period. Repetition rote of pulse

is

the

same

as

that

of '

A'

time

bose

generator

.

'

A'

+

Gate-Positive-going

signal

approximately

25 volts

peak-to-peak, with a pulse duration

equal

to the duration of

'A'

sweep

and

a repetition rote

equal

to

that

of

the '

A'

time

bose

generator.

'8'

+

Gate

-Positive-going signal

app

roximately 25 volts

peak-to-peak, with a pulse duration

equal

to the duration of

'B'

sweep

and

a repetition rote

equal

to

that

of the '

B'

ti

me

base

generator

.

'A' Sawtooth-Time bose 'A'

sweep

sawtooth waveform,

150 volts

in

amplitude.

'B

'

Sawtooth-Time

bose

'B'

sweep

sawtooth waveform,

150 volts

in

amplitude.

Ventilation

Separate

forced filtered air systems for the two units.

In

the event of overheating, the self-resetting thermal relay

interrupts instrument

power

.

Construction

Aluminum-alloy ·chassis

and

cabinets. Photo-etched ano-

dized front panels; blue vinyl-finished cabinets

and

rear

panels. Side

and

bottom panels

separately

removable.

Dimension!!

Indi

cator

Unit-13 inches wide; 20 inches high; 24 inches

deep

.

We

ight without vertical plug-in units: 68 pounds.

Power Supply

Unit-13

inches wide; 10 inches high; 171

/2

inches

deep

.

Weight

: 45 pounds.

Standard

Accessories

1- Time bose plug-

in

extension (013-013)

4- Attenuotor probes, 1

OX

Attenuation

(01

0-127)

l- Inter-unit

power

cable

(01

2-

032)

2-

BNC

to binding post

adapt

ers (103-033)

1-3

Characteristics-

Type

555/21

A/22A

1-Test

lead

(012-031}

1-Polarized

light filter (378-545}*

1-3-conductor

power

cord

(161-01

0}

1-3

to 2-wire

adapter

(1

03-013}

2-lnstruction

manuals

(070-403}

SPECIAL-PURPOSE

VERTICAL

PLUG-IN

UNITS

Type

N

The Type N Sampling Unit

when

used

with the Type 555

Oscilloscope permits

observation

of

repetitive signals with

fractional

nanosecond

(1

0·9 second} risetimes.

Samples

of

the input signal

are

taken,

each

sample

on a different cycle

of the signal

and

slightly farther

along

the

waveform,

and

the input signal

is

reconstructed on a relatively long

equiva-

lent time

base

. Characteristics

of

the

Type

N include: 0.6

nanosecond

risetime,

corresponding

to a

passband

of

approx-

imately 600

me;

10 millivolts

per

centimeter

input deflection

factor with less

than

2 millivolts of system noise; ± 120-milli-

volt

dynamic

range;

equivalent

sweep

rates

from 1

nanosec-

ond

per

centimeter to

10

nanoseconds

per

centimeter.

Type

0

The Type 0 Plug-In Unit

is

a

dual

channel

operational

amplifier

capable

of

performing the

operations

of

integra-

tion, differentiation, function

generation,

and

linear

and

non-

linear amplification.

When

used with

the

Type 555 Oscillo-

scope

the

passband

of

each

channel

is

de

to 25

me.

The

two

channels

can

be

used

in

series to

perform

two

operations

simultaneously, such

as

double

integration.

Input

impedances

can

be

selected

from 5 resistance

values,

from 10 kilohms to 1 megohm,

and

6

capacitance

values,

from 10

picofarads

to 1 microfarad. Selection

of

feedback

impedances

is

from

an

identical

range

of

values.

Output

amplitude

is

±50 volts

and

±5milliamps,

and

output

im

-

pedance

is

approximately

30

ohms.

Type

P

The

Type

P Plug-In Unit

generates

a fast rise

step

-function

test signal

of

known

waveform,

simulating the

output

of

an

ideally

compensated

Type K Unit driven with a Tektronix Type

107

Square-Wave

Generator

. The Type P permits the

stand

-

ardization

of

the main-unit vertical amplifier transient

response

of a Tektronix plug-

in

type

oscilloscope. Pulse repetition

rate

is

240

step

functions

per

second, with

either

positive

or

nega-

tive

polarity

. Step function

amplitude

is

continuously

adjust

-

able

between

0

and

3 major

graticule

divisions. Pulse rise-

time

is

approximately

4

nanoseconds.

Type

Q

The Type Q Plug-

In

Unit permits

any

Textronix plug-in

type

oscilloscope such

as

the Type 555 to

be

operated

with strain

gages

and

other

transducers. Excitation

voltages

for the

strain

gages

and

transducers

are

provided

by the plug-in

unit. The unit

provides

high

gain,

low noise,

and

extremely

'for

instruments

in

serial

number

ronge

7000

-

8999,

light

filter

is

green

plastic

(378-514).

Green

filter

is for

use

with

external

groticule;

polarized

filter

is

for

internal

graticule

crt.

1-4

low drift. Frequency

response

of

the

Type

Q Plug-In Unit

is

de

to

6

kc;

risetime

is

approximately

60

microseconds. Strain

sensitivity

is

calibrated

in

10

steps

from

10

microstrain

to

10,000 microstrain

per

major

graticule

division

and

is

con-

tinuously

variable

between

steps

.

TypeR

The Type R Plug-In Unit

is

a

combined

power

supply

and

pulse

generator

which

is

used

to

measure

the

high-frequency

characteristics

of

junction transistors

by

the

pulse-response

method

.

When

the

Type

R

is

used

in

the

Type

555

Oscillo-

scope,

delay

time, risetime,

storage

time,

and

falltime

may

be

displayed

simultaneously.

Calibrated

vertical

deflection

factors

range

from 0.5 milliamp

to

100 milliamps

per

centi-

meter. A

pushbutton

switch

connects

a front-

panel

terminal

directly

to

the

input

of

the

oscilloscope

for

observing

exter-

nally

derived

waveforms.

Pulse risetime

of

the

Type

R Unit

is

less

than

5

nanoseconds

and

minimum

displayed

risetime with

the

Type

555

Oscillo-

scope

is

about

12

nanoseconds.

Pulse

amplitudes

range

from

50 millivolts

to

10

volts

in

8

calibrated

steps

and

variable

between

the

steps

. Repetition

rate

is

120 pulses

per

second.

TypeS

The

Type

S Plug-In Unit

is

designed

to

test

certain

semi-

conductor

diode

parameters,

such

as

junction

resistance

,

junction

capacitance,

and

the

stored

charge

at

the

junction.

Performance

of

a

diode

in

a

particular

circuit

can

be

pre

-

dicted

by

analyzing

the

recovery

and

"turn-on"

characteris-

tics. Since

it

is

essentially

a

means

for plotting

voltage

across

an

element

while

passing

constant

current

through

it, the unit

can

be

used

for

other

applications

as

well. For

example,

observing

the junction

characteristics

of

transistors,

or

meas-

uring the resistance,

capacitance

or

inductance

of

circuit

components

.

The

Type

S offers

calibrated

forward

currents

in

five fixed

steps

from 1 to 20 milliamps,

and

reverse

currents

calibrated

in

six

steps

from 0

to

2 milliamps.

Diode

shunt

capacitance

is

9

picofarads,

and

deflection

factors

ore

0.05

and

0.5 volts

per

centimeter

calibrated.

Type

Z

The

Type

Z Plug-In Unit

extends

the

accuracy

of

oscillo-

scope

voltage

measurements.

It

can

be

used

in

three

modes

of

operation:

(1}

as

a

conventional

preamplifier,

(2}

as

a dif-

ferential input

preamplifier,

or

(3}

as

a

calibrated

differential

comparator

.

With

sensitivity

of

50

mv

/em

and

insertion volt-

age

range

of

± 100 volts,

the

effective

scale

range

is

±2000

em. Maximum resolution

of

the

Type

Z Unit

is

0.005%.

As a

conventional

preamplifier,

the

Type

Z Unit offers a

passband

of

de

to

13 me with

the

Type

555 for

signals

that

do

not

overscan

the

screen. The deflection

factors

ore

0.05

volts/em

to

25 v/ cm

in

9 fixed,

calibrated

steps

.

As a differential input

preamplifier,

the

Type Z

accepts

a

common

-

mode

signal level ± 1

00

volts

at

minimum deflec-

tion factor,

and

offers a

common

-

mode

rejection

ratio

of

40,000 to 1. Maximum input signal

rate

of

change

is

+1

volt

/7

nsec,

or

-1

voltf5 nsec.

As a

calibrated

differential

comparator,

the

Type

Z

has

three

comparison

voltage

ranges

:

zero

to ± 1 volt,

zero

to

± 10 volts,

and

zero

to + 100 volts.

®

SECTION 2

OPERATING

INSTRUCTIONS

GENERAL INFORMATION

The Type 555

Oscilloscope

is

a versatile instrument which

is

adaptable

to

a

great

number

of

applications.

To

make

full

use

of

the potentialities

of

the

instrument, you should

become

familiar with the function

and

operation

of

each

of

the

vari-

ous controls.

This

section

of

the

manual

provides

the

basic

information

required

for

operation,

including the functions

of

the controls, the use

of

input

cables

and

probes,

tri

ggering

of

the

sweep,

and

operation

of

the

delayed

sweep

feature.

Horizontal Sweep

The

two

plug-

in

'time

base

units

produce

the

horizontal

deflection (sweeping)

of

the two

cathode-ray

tube

beams

.

Either

beam

can

be

deflected

by

either

time

base

unit,

or

both

beams

can

be

swept

simultaneously

by

the

same

unit.

The

Upper

Beam

and

Lower Beam HORIZ.

DISPLAY

switches

are

used

to

select the time

base

units

to

drive

the

separate

beams.

In

most

applications,

the

SWEEP FUNCTION switches

are

used

in

the AUTO

BASELINE

or

NORMAL positions. These

two positions

provide

normal

triggered

operation

of

the

time

base

units.

In

addition,

the

AUTO

BASELINE

provides

an

automatic

sweep

of

the

trace

when

no

signal

is

applied

to

the triggering circuit.

Other

positions

of

the

SWEEP FUNC-

TION switch permit use

of

the single

sweep

and

delayed

sweep

modes

of

operation.

The

sweep

rates

of

the

two

beams

are

determined

by

the

settings

of

the

appropriate

TIME/CM

and

HORIZ.

DISPLAY

switches.

In

turn, the

sweep

rate

determines

the

duration

of

the

trigger

holdoff

period

. The

two

time-base

units

have

identical

sweep

characteristics. There

are

24

calibrated

sweep

rates

ranging

from

.1

p.seconds to 5

seconds

per

centimeter.

Uncalibrated

VARIABLE

controls permit

the

sweep

rates

to

be

varied

continuously

between

the

steps

of

the

TIME

/CM

switches,

and

can

extend

the

sweep

rate

to

about

12

seconds

per

centimeter when

the

switch

is

in

the

5

SEC

position.

Sweep Triggering

The oscilloscope

display

is

formed

by

the repetitive

sweep

of

the

crt

beam

from left to right

across

the

oscilloscope

screen while

an

input

voltage

signal

produces

vertical

deflec

-

tion

of

the

beam

.

If

the

sweeps

were

allowed

to

occur

at

random,

or

at

some

rate

not

the

repetition

rate

of

the

input signal,

the

displayed

waveform

would

be

traced

out

at

a different horizontal position

each

time

and

the

woveshope

would either

be

indistinguishable

or

would

drift across the screen.

In

most cases

it

is

desirable

for a repetitive

waveform

to

appear

stationary

on

the

oscilloscope screen so

that

the

cha

racteristics

of

the

wav

eform

con

be

examined

in

detail.

To

produce

a

stationary

display, the

start

of

each

sweep

must

be

time-

the

repetition

rote

of

the

input signal.

In

the Type 555 Oscilloscope,

the

starting

time

of

the

sweep

is

the

displayed

waveform

by

using the input sig-

®

nal

or

another

time-related

signal to

start

(trigger) the

sweep

.

Figure

2-1

shows the time-relationship

between

the input sig-

nal, the triggering signal,

and

the

horizontal

sweep

voltage

for a typical sine-wave

display

. The triggering signal

is

superimposed on a holdoff waveform so the crt

beam

con

retrace

to the left

of

the screen

and

be

ready

to

sweep

again

before the trigger signal

is

allowed

to

start

a new

sweep.

Input

Signal

I

''--;,....

___

_

------------+---

' ' I

1

Triggering

and

Holdoff

Signal

I I

. I

I

Horizontal

Sweep

1

rvv1

rv

I I

Crt

Display

Fig. 2-1 .

Ladder

diagram

showing

waveform

sequence

in

triggered

sweep

operation.

INSTALLATION

The two

un

its

of

the

os

ci

llos

cope

should

be

placed

so

that

air

can

circulate freely

about

them. Ventilation

is

provided

by

fans

in

the

separate

u

r,

its

that

draw

air

in

through filters

at

the

rear

of

the

un

its.

Side

panels

should

be

in

place

for

proper

operation

.

Never

operate

th

e oscilloscope without

the fans

operating

.

If

the inteonol

temperature

in

either

un

!t

becomes

too

high, a the

rm

al cutout w

ill

open

and

disconnect

the

power

until

the

t

emper

atur

e

has

returned to normal.

If

this occurs, check

the

air

filt

ers

and

the

clearance

around

th

e

units. A constant

temp

erature

is

important

for

accurat

e

oper

-

ation

of

the instrument. Keep the

air

filters

clean

in

accord

·

onc

e with the instructions given

in

th

e

Maintenance

section

of

this manual.

Transformer Conver

sion

This instrument

is

wired

lo

operate

with the line

voltage

indicated

on the

tog

adjac

e

nt

to the

power

plug on the

Power Supply Unit.

Li

ne freq

u<=

ncy must

be

between

50

and

60 cycles. The transformer

cc.

;1

be convented for

operation

2-1

Operating

Instructions-

Type

555/21A/22A

on nominal line

voltages

of 117 volts

or

234 volts, by

chang

-

ing connections on the

two

transformers, the fans

and

the

saturable

reactor

. Rewire

according

to

the

diagrams

shown

on the Decoupling

Network

schematic

diagram

.

Fuse

data

is

given

in

the

electrical Parts list for

replacing

fuses

or

converting

to

another

line

voltage

.

SELECTION

OF

PLUG-IN UNITS

The Type 555 Oscilloscope

is

designed

to use Tektronix

letter-series

and

1-series plug

-i

n

un

its

as

th

e input

stages

for

the two vertical deflection systems,

and

Types

21

A

and

22A

Time-Base Units to

generate

the horizontal

sweep

voltages

.

The use

of

plug-in units

at

the vertical inputs permits you

to

change

the vertical characteristics

of

the

oscilloscope to

meet a wide

range

of

application

requirements. The

par

-

ticular plug-in units to

be

used must

be

selected to satisfy the

requirements

of

your applications.

In

selecting the vertical

plug-in units,

yo~

must consider

the

bandpass

, risetime,

de

-

flection factor

and

number

and

type

of

inputs

required

.

Plug-

in

type

time-

base

units

are

used primarily for

ease

of

servicing

and

calibration

. The plug-

in

extension

accessory

supplied with the Type 555 allows

the

instrument

to

be

operated

with either time

base

unit

partia

l

ly

extended

from

the oscilloscope. For normal

operation,

the Time Base Units

are

left

in

the Type 555,

and

are

held

in

place

by

thumb-

screws

located

at

the

rear

of

the time-

base

compartments

.

The side

panels

of the oscilloscope must

be

removed

to

gain

access

to

the retaining screws (see

Fig

. 2-

2)

.

Fig.

2-2

. Location

of

the

lime-base

and

vertical plug-in locking

screws.

Normally,

a Type

21

A Time-Base Unit

is

used

in

the

Time

Base A plug-

in

compartment,

and

a Type 22A Time-Base Unit

in

the Time Base B

compartment

. Either a Type

21

A

or

a

Type 22A

may

be

us

ed

for Time Base A; however, a Type

2-2

22A must

be

us

ed

for Time Base B

in

order

to

use

the

delayed

sweep

feature

of

the

instrument.

The Type 555

Oscilloscope

should

not

be

used

without

all

of

the

plug-

in

units installed

or

connected

by

extensions.

Operating

the instrument with a

plug

-

in

unit missing will

not

damage

the

oscilloscope,

but

may

cause

the

power

sup

-

plies to

go

out

of

regulation

due

to

insufficient

loading.

The

instrument will

not

operate

correctly unless

the

power

sup

-

plies

are

regulating

.

FRONT

AND

REAR-PANEL CONTROLS

All

controls

and

connectors

required

for

the

operation

of

the Type 555

are

located

on

the

front

panels

of

the

oscillo-

scope

and

its plug-

in

units

and

on

the

rear

panel

of

the

oscilloscope (s

ee

Fig. 2-3). Some

of

the controls which

have

complex

functions

are

treated

in

greater

detail

later

in

this

section,

in

the discussions

of

the

various

modes

of

operation.

FUNCTIONS

OF

CONTROLS

AND

CONNECTORS

AMPLITUDE

CALIBRATOR

Switch

CAL

OUT

Connector

SCALE

ILLUM.

Control

Indicator Unit

Sets

the

amplitude

of

the

1

kc

(approx.)

square

-

wave

signal

available

at

the

CAL

OUT

connector

. Amplitude

is

adjustable

in

18

steps

from .2 millivolts

to

100

volts,

peak-to

-

peak.

Provides 1

kc

square

-

wave

output

primarily

for checking

gain

of

the

vertical deflection

systems

and

for adjusting

compensation

of

probes

.

Amplitude

of

output

signal

is

controlled

by

AMPLITUDE

CALIBRATOR

sw

itch.

Controls intensity

of

graticule

illumination

lamps. Rotate clockwise

to

increase

illum-

ination; counterclockwise

to

decrease

illum-

ination. The

lamps

edge-light

the

graticule

markings for

accurate

time

and

voltage

measurements

.

DELA

YEO

Sets time

duration

between

triggering

of

TRIGGER FROM

'A

'

sweep

and

output

of

Delayed

Trigger

TIME

BASE

A pulse.

(Operates

with Time Base A

TIME

/

(1

-10

MULTIPLIER)

CM control.)

Delayed

trigger

pulse

is

de

-

DELAYED

TRIG

. OUT

Connector

INTENSITY

Control

livered

to

DELA

YEO

TRIG

.

OUT

connector

and

to

Time Base B Trigger circuit for

de

-

layed

sweep

operation.

Provides a

delayed

trigger

output

pulse

from Time Base A for

triggering

an

exter-

nal device.

Delay

time

is

determined

by

setting

of

Time Base A TIME/CM switch

and

DELAYED

TRIGGER (1-10

MULTIPLIER)

control. (See Fig

2-1

0).

Upper Beam and Lower Beam

Adjusts

the

brightness

of

the

display

to

compensate

for

changes

in

brightness

caused

by

changing

the

sweep

or

trigger

-

ing

rates

. Rotate control clockwise

to

in-

crease

brightness; counterclockwise

to

de

-

crease

brightness.

FOCUS Control

HORIZ.

DISPLAY

Switch

HORIZ.

POSITION

Control

Beam-Position

Neons

CRT

CATHODE

Connector

(rear

panel)

CAUTION: Excessive intensity

can

perma-

nently

damage

the

phosphors

of

the

crt

screen. Use

the

INTENSITY control

to

keep

the

beam

brightness

turned

down

below

the

level

that

causes

a

halo

to form

around

the

crt

spot

or

trace.

Adjusts focus

of

crt

spot

or

trace

. Adjust

for mimimum

trace

width

or

spot

diameter

.

The internal ASTIG. control for

the

respec-

tive

beam

also

affects

the

focus

of

the

beam

.

See

the

Calibration

Procedure

for

adjustment

of

the

ASTIG. control.

Selects

source

of

horizontal

deflection

volt-

age

from

either

time-

base

unit

or

from

the

external

horizontal

input. Also selects

either

an

unmagnified

(X1)

display

or

SX

magnification

(X

.

2)

of

the

time-base

sweep

rate

and

X1

or

X1

0

attenuation

of

an

ex-

ternal

horizontal

input signal.

Controls

horizontal

position

of

crt

spot

or

trace;

positions

any

portion

of

a

magnified

display

onto

the

crt

screen

. Single knob

controls

both

coarse

and

fine

adjustment

of

the

beam

position, using a

"backlash"

coupling

between

the

two

controls.

Indicate

the

electrical position

of

the

trace

or

spot,

whether

on

or

off

the

crt

screen

.

Small

arrows

beside

the

lamps

indicate

the

direction

of

the

beam

from

the

center

of

the

screen

. Both

horizontal

lamps

may

light during

the

sweep

of

the

dot

if

the

sweep

rate

is

slow;

both

vertical

lamps

will

be

unlit

if

the

display

is

centered

vertically.

Permits

application

of

external

signal for

intensity

modulation.

Negative-going

in-

creases

intensity; positive-going

decreases

intensity. 10-volt signal

change

produces

appreciable

intensity

modulation.

leave

connector

grounded

except

when

applying

external

signal.

CRT

CATHODE Selects intensity

modulation

signal from

Switch internal multi-trace

chopped

switching

or

externally

applied

signals

through

CRT

CATHODE

connector.

leave

switch

in

CRT

CATHODE position

except

when

operating

in

chopped

mode.

EXT.

HORIZ. Permits

application

of

external

voltage

sig-

INPUT

Connector

nal for

horizontal

deflection

of

crt

beam.

EXT

. HORIZ.

GAIN

Control

Front-panel HORIZ.

DISPLAY

switch must

be

in

one

of

the

EXT.

ATIEN positions.

Controls

amount

of

horizontal deflection

produced

by

externally

applied

voltage

.

Horizontal

deflection

factor

is

continuously

varia

ble

from

approximately

0.2 to 2

volts/

em with HORIZ.

DISPLAY

switch

EXT

.

AT-

TEN

.

X1;

from 2

to

20

volts/

em with switch

at

EXT

ATIEN.

X10.

Time

Base

A

and

Time Base B

Trigger INPUT

Connector

Permits

application

of

triggering

signal

from

an

external

source

that

is

time-

Instructions-

Type

555/21A/22A

Trigger

SOURCE

Switch

Trigger

COUPLING

Switch

Trigger SLOPE

Switch

Trigger

LEVEL

Control

Trigger

VERNIER

Control

SWEEP

FUNCTION

Switch

TIME/CM

Switch

VARIABLE

Control

to

the

input signal. Set

trigger

SOURCE

switch

to

EXT.

to

use

external

trigger.

Selects

the

source

of

the

triggering signal

from

one

of

six sources:

UPPER

BEAM

or

LOWER

BEAM

input

signal,

from

the

trigger

pickoff

in

the

Vertical Amplifier

of

the

respective

beam;

UPPER

BEAM

PLUG

-

IN

or

LOWER

BEAM

PLUG-IN, from the

trigger

pick-

off

in

the

vertical plug-in unit. (These

positions

apply

only to multi-trace plug-

in

units with

trigger

pickoff);

LINE

signal, from

the

regulated

oc

Cir-

cuit (50 to

60

cps);

EXT

.

trigger

signal

applied

through ex-

ternal

trigger

INPUT

conector

.

Selects

either

oc-

or

de-coupling

of

the

input

triggering

signal

whether

from inter-

nal

or

external

source.

Selects

either

the

rising (

+)

portion

or

the

falling

(-)

portion

of

the

triggering

wove

-

form for

triggering

the

sweep

(see Fig. 2-6).

Selects

triggering

waveform

level

that

causes

trigger

circuit

to

start

a

sweep.

Operates

over

a ± 10-volt

range.

Selects

triggering

level

over

a ± 1-volt

range

for fine

adjustment

or

for use on

small

triggering

signals.

Selects

mode

of

sweep

operation

from five

basic

modes:

NORMAL;

AUTO

BASELINE;

SINGLE SWEEP;

SWEEPS

ONCE

FOR

EACH

"A'

DLY

'D

TRIG.;

TRIGGERABLE

ONCE

FOR

EACH

'A'

DLY'D

TRIG

.

(The last

two

positions

are

only on the

Type

22A.)

See

text

for specific

mode

of

operation.

Sets

sweep

rote

of

the

beam

(or beams)

using

that

time-base

unit for

generation

of

the

sweep

voltage.

Sweep

rates

range

from

.1

p.seconds

to

5

seconds

per

centi-

meter

.

Varies

sweep

rate

continuously

between

steps

of

TIME

/CM switch,

and

extends

sweep

rote

to

about

12

seconds

per

centi-

meter

with switch

in

the

5

SEC

position.

Sweep

rate

is

not

calibrated

when using

VARIABLE

control.

leave

control in

CALI-

BRATED

positi

on

for making time measure-

ments.

UNCALIBRATED

lights

when

the

VARIABLE

Control

is

not

Neon

in

CALIBRATED

position.

2-3

Operating

Instructions-

Type

555/21A/22A

Fig.

2-3.

Front-

and

rear-panel

controls

and

connectors.

2-4 ®

PUSH

TO

RESET

Resets Single Sweep lockout circuit to a

Button triggerable condition.

READY

Neon

STABILITY

Adjustment

SAWTOOTH

Connector

+GATE

Connector

POWER

ON

Switch

Power Indicator

lamp

lights when Single Sweep lockout circuit

is

in

triggerable condition; light

goes

out

when sweep

is

held off after single sweep

of the crt.

Sets input level of Sweep

Gate

circuit for

stable

triggering.

Provides output

of

horiz.:>ntal

deflection

voltage waveform, 150 volts peak-to-peak,

capable

of driving

or

triggering external

devices. Time Base B sawtooth waveform

includes

delay

time when operating

in

de-

layed mode.

Provides output of sweep gating waveform,

20 volts peak-to-peak. Time Base B

+Gate

waveform contains delay time when

oper

-

ating

in

delayed

mode.

Power

Supply

Unit

Applies line power

to

low-voltage power

transformers. A time-delay relay allows

the tube cathodes to warm up before de

power

is

applied

to circuits.

Indicates that

ac

line voltage

is

applied to

the low-voltage circuit.

Output

Signals

Several low-impedance signal outputs

are

available

at

the

front panel of the Type 555 Oscilloscope sytsem. These are:

an Amplitude Calibrator square wave; a Delayed Trigger

pulse; a

+Gate

waveform from each time-base unit;

and

a

Sawtooth waveform from each time base. Typical wave-

forms

are

illustrated

in

Fig.

2-4.

In

addition, some multi-

trace vertical plug

-i

n units provide

an

amplified single-

channel signal output for triggering oscilloscopes from only

one

input signal.

In

the Type 555, these units

apply

the

single-channel signal to the triggering circuits through

in-

ternal wiring.

Use

of

the

+Gate

and

Sawtooth waveforms for trigger-

ing or driving external devices

is

illustrated

in

Fig.

2-8.

In

this application, the time-base unit

is

usually set for a free-

running sweep.

Calibrated

Graticule

The

edge

-lighted internal graticule

is

accurately marked

with 10 horizontal

and

6 vertical 1-centimeter divisions

and

2 millimeter subdivisions marked on the vertical centerline

and

the two horizontal centerlines. The deflection factors of

the crt beams

are

calibrated to these graticule marks.

Thus

the marks provide a calibrated scale for making time

and

voltage measurements.

To

protect the

bonded

plastic faceplate of the internal

graticule crt (instrument

S/N's

9000-up), always use a scratch

shield

or

plastic light filter

in

front

of

the crt. The shield

and

filter

are

provided with the instrument.

For

normal

viewing

and

for photographing the display, use the clear

plastic scratch shield. For viewing under bright ambient

light conditions, use the light filter to provide better trace-

to-screen contrast. When using the light filter, however, be

careful not to set the beam intensity so high that

it

will

burn

the crt phosphor.

Operating

Instructions-

Type

555/21A/22A

I I

-7 Volts:.l

__.,.

Selected

I

voltage

amplitude

I I

t-

r-

1

Del~y

t--

'-I

tije

.l

...

~

I

Frequency - 1

kc

T -

-

25

Volts

..1.

r-

.I

-

~

Sweep'4

~

I

tir

1---1

1--

T

150

Volts

.i

/ v

v /

v / v

v.

.

v

.....

d.

Sweep

...

It-!-

I

rmi

I

r-

DELAYED

TRIGGER

AMPLITUDE

CALIBRATOR

+

GATE

SAWTOOTH

Fig.

2-4.

Output

waveforms

available

at

the

front

panel.

For instruments with external graticules (S/N's 7000-8999),

the color of the graticule illumination may be changed

from white to red, or vice versa, by rotating the graticule

180°.

Vertical Controls

The vertical plug-

in

unit for

each

beam contains all the

front-panel vertical positioning

and

deflection controls for

that beam. Refer

to

the instruction manuals

of

the particular

plug-

in

units for operation of the vertical controls.

CONNECTING

TO

THE

SIGNAL

SOURCE

Input signals

t~at

are

to be displayed

as

vertical deflection

on the crt screen

are

applied

to the input connectors on the

two vertical plug-

in

units.

Use

of

Coaxial

Cables

In

general, coaxial cables should

be

used to connect the

signal source to the vertical input. The use of coaxial cables

nearly eliminates pickup from stroy electromagnetic fields,

and

also eliminates radiation from the connecting cables by

grounding the outside conductors.

It

is

sometimes possible to

use

an

unshielded input lead

if

the signal amplitude

is

high

and

if

its

frequency

is

low.

When

an

unshielded

lead

is

used,

2-5

Operating

Instructions-

Type

555/21A/22A

connect

another

lead

between

the oscilloscope chassis

and

the chassis

of

the signal source.

In

high-frequency work

it

is

usually necessary

to

terminate

signal sources

and

connecting

cables

in

their characteristic

impedances. Unterminated connections result

in

signal reflec-

tions within the

cables

and

cause

distortion of the

displayed

waveforms. The input

coaxial

cable

will often serve to termi-

nate

the signal source,

and

a termination

placed

at

the input

of the plug-in unit will provide sufficient termination for sig-

nal reflections. However,

if

the source

impedance

is

consid-

erably

different from

that

of the connecting

cable,

the source

end

of the

cable

may

also

need

to

be

terminated.

When

connecting

an

input signal,

the

loading

effect

of

the

oscilloscope on the signal source must

be

considered. The

resistance

at

the input

of

the vertical plug-in unit

is

usually

1 megohm which

adequately

limits low-frequency

loading

to

a negligible

value

. However,

at

high frequencies, the input

capacitance

of the vertical plug-

in

and

the distributed

ca

-

pacitance

of the input

cable

becomes

significant.

Capaci-

tive

loading

at

high frequencies

may

be

sufficient

to

ad-

versely affect both the

displayed

waveform

and

the

opera

-

tion

of

the signal source. Attenuator

probes

can

be

used

to

reduce

capacitive

and

resistive

loading

to

very small

values

.

Use

of

Probes

In

addition

to reducing the

load

on the signal source,

an

attenuator

probe

also

decreases

the

amplitude

of

the

dis-

played

waveform by

the

attenuation

factor

of the

probe

. This

permits observation of signals

beyond

the normal

amplitude

limits

of

the oscilloscope

and

plug-

in

combination. Signal

amplitudes, however, must

be

limited

to

the maximum allow-

able

value

of the

probe

being used.

Before a

probe

is

used,

it

must

be

compensated

to

operate

properly

with the plug-in unit.

Compensation

of the

probe

is

adjusted

according

to the

procedure

given

in

the instruction

manual with the vertical plug-in unit

and

in

the instructions

accompanying

the

probe

.

In

general,

this adjustment

is

done

by connecting the

probe

cable

to

one

of the vertical inputs

and

observing several cycles of

the

calibrator

waveform

on the crt screen. The compensating

capacitor

is

then

ad

-

justed to provide minimum distortion

of

the

top

and

leading

corner of the

square

-

wave

signal (see

Fig

. 2-

5)

.

TRIGGERING

THE

SWEEP

For most

applications

the oscilloscope

sweep

must

be

trig-

gered

by some signal

that

is

time-related to the input signal

being

observed

on the crt. This section discusses the selection

of a suitable triggering signal

and

the

use of the triggering

controls.

-------

~

._

\...

.

r r ! (

Incorrect

\...

Internal Triggering

Sources

Either time-base

un

it

can

be

triggered

internally from the

Upper

Beam Vertical Amplifier,

the

lower

Beam Vertical

Amplifier, the

Upper

Beam plug-

in

unit,

the

lower

Beam

plug-

in

unit, or

the

power

line signal.

In

addition,

an

external

source

can

be

used for triggering with the

trigger

signal

applied

to the

external

trigger

INPUT connector

on

the time-

base

unit. Selection

of

the triggering signal

is

made

with the

SOURCE switch.

It

is

usually most convenient

to

trigger

internally from

one

of

the

input signals by setting the SOURCE switch

to

either

UPPER

BEAM

or

LOWER

BEAM

.

With

the switch

in

one

of

these

positions, a

sample

of the vertical signal

is

picked

off

from the

selected

Vertical Amplifier circuit

and

applied

to

the Trigger circuit.

\...

If

a multi-

trace

plug-in unit with single-channel

trigger

pick-

off

is

used,

set

the SOURCE switch

to

UPPER

BEAM

PLUG-IN

or

LOWER

BEAM

PLUG

-

IN

to

apply

the single-channel signal

internally

to

the Trigger circuit.

When

a multi-

trace

display

is

triggered

in

this manner,

each

trace

is

triggered

at

the

same

point

each

time, relative

to

the

channel used for

triggering.

NOTE

If

a

Type

555

with

Serial

Number

7000

or

above

is

to

be

used

with

Type

21

and

Type

22

Time-Base

Units,

the

wire

between

19

on

the

interconnect-

ing

plug

and

the

ceramic

strip

(inside

each

time-

base

unit)

should

be

removed

.

Otherwise

the

oscil-

loscope

will

not

be

compatible

with

multi-trace

verti-

cal

plug

-

in

units with

single-channel

pickoff.

If

a

Type

555

with

Serial

Number

below

7000

is

to

be

used

with

Type

21A

and

Type

22A

Time-

Base

Units,

the

oscilloscope

will

need

to

be

modified

to

provide

internal

connection

of

the

multi-trace

single-

channel

triggering

signal.

Without

the

modification,

the

UPPER

BEAM

PLUG-IN

and

LOWER

BEAM

PLUG-.

IN

positions

of

the

SOURCE

switches

are

discon-

nected.

Order

modification

kit

number

040-328.

Triggering from the

power

line

is

sometimes useful when

the vertical input signal

is

time-

the line frequency.

This

type

of

operation

is

used when the input signal

is

not

satisfactory for triggering. Set the SOURCE switch

to

LINE

for

stable

triggering on the constant-

amplitude

line-frequency

waveform.

\...

I...

\.,

J,.

....

1-

- - - ----

-

....

,

~

Incorrect Correct

Fig

.

2-5.

Probe

compensation

waveforms.

2-6

External Triggering Sources

If

a triggering signal

is

required with characteristics other

than those of the input signal,

it

can

be

applied

by means of

the external trigger

INPUT

connector. The signal may

be

introduced through a jumper lead, a coax

cable,

or

a probe

connected

to

the trigger

INPUT

connector. Set the

SOURCE

switch on the time-base unit

to

EXT.

External triggering

is

convenient for signal-tracing

in

a

device under test. The triggering signal can

be

taken from

any

convenient point

in

the circuit, then signals can

be

observed anywhere

in

the circuit without readjusting the

triggering controls. Phase-

and

time-relationships between

the signals

can

be

determined directly from the crt display

when the triggers

are

taken from a single source.

This

is

particularly useful with multi-trace plug-in units.

Triggering from

an

external source increases the accuracy

of

time-jitter measurements when

the

trigger source

is

more

stable

than the displayed input signal.

Triggering Controls

The trigger

SLOPE

switch provides selection of triggering

from either the rising (+ slope)

or

falling

(-

slope) portion

of

the

triggering waveform (see

Fig

.

2-6).

In

many applica-

tions it

is

necessary

to

trigger on the proper slope

to

provide

the desired display, although some waveforms can

be

trig-

gered

on either slope. Generally,

the

steepest portion of the

waveform will provide the most

stable

triggering, but final

selection of the triggering slope will

depend

on both the

nature of the triggering signal.

and

the type

of

display

desired.

Sweep

triggen

on

+

slope

LEVEL

or

VERNIER

!(5\

Waveforms

obtained

with

LEVEL

control

set

in

the

+ region

Sweep

triggers

on

-slope

SLOPE

~+

f7

I\ I\

LEVEL

or

VERNIER

!(5\

Waveforms

obtained

with

LEVEL

control

set in

the

-region

Fig.

2-6

. Effects

of

the

trigger

SLOPE,

LEVEL

and

VERNIER

controls.

Operating

.

Instructions-

Type

555/21A/22A

The trigger

COUPliNG

switch determines whether the trig-

gering signal

is

ac

or

de-coupled

to

the Trigger circuit. The

AC

position

of

the

COUPliNG

switch

is

used for most appli-

cations, since triggering

is

then not affected

by

the vertical

position of the waveform on the crt screen. The

DC

position

of the switch should

be

used

if

triggering

is

desired

at

a par-

ticular de level,

or

if

triggering

is

done on very low frequency

signals.

The trigger

LEVEL

and

VERNIER

controls

set

the level on

the triggering waveform where triggering occurs (see

Fig.

2-6).

These

are

the last controls to

be

set when triggering

the display. The

LEVEL

control, which

operates

over a

-+-

1

0-

volt range,

has

ten times the effect of the

VERNIER

control.

To

trigger

the

sweep, center the

VERNIER

control

and

rotate the

LEVEL

control until a stable display of the wave-

form

is

presented on the crt screen. Fine adjustment of the

triggering level can then

be

made

with the

VERNIER

control.

Turning counterclockwise causes triggering

at

a more nega-

tive point on the waveform,

and

turning clockwise causes

triggering

at

a more positive point. Normally these controls

are

approximately centered when the display

is

properly

triggered. The

VERNIER

control

is

convenient for adjusting

the trigger level when small

or

high-frequency triggering sig-

nals

are

used.

FIRST-

TIME

OPERA

liON

The following procedure

is

suggested for setting the

in-

strument

in

operation

to

display the input signals. Dual-

beam

operation

is

illustrated.

Connect the two main units of the instrument together with

the inter-unit

cable

and

connect the Power Supply Unit to the

power line. With time-base

and

vertical plug-in units

in

-

stalled

in

the lndicatqr Unit, set front-panel controls to the

following positions:

Upper

Beam

FOCUS Centered

INTENSITY

Counterclockwise

HORIZ.

DISPLAY

TIME

BASE

A

Xl

Lower Beam

FOCUS Centered

INTENSITY

Counterclockwise

HORIZ

.

DISPLAY

TIME

BASE

B

Xl

Time

Base

A

and

Time

Base

B

TIME/CM

VARIABLE

SWEEP

FUNCTION

LEVEL

SLOPE

COUPLING

Set

to

display 2 or 3 cycles of the

input waveform;

if

unknown, start

with .5

mSEC.

CALIBRATED

AUTO

BASELINE

Clockwise

Set to + for positive slope; - for

negative slope,

as

desired.

AC

for most signals;

DC

for

lo

w-

frequency triggering.

2-7

Operating

lnstrudions-

Type

555/21A/22A

Time

Base A

UPPER

BEAM

SOURCE

Time Base B

LOWER

BEAM

SOURCE

Vertical Plug-In Units

Deflection Factor Set to produce 2

or

3

em

of

deflec-

tion on crt screen.

Input Coupling

AC

for most signals;

DC

for deter-

mining de levels.

Connect input signals

to

the vertical input connectors

of

both beams as described previously. If

an

external trigger-

ing signal

is

desired, connect

it

to the external trigger

INPUT

connector

and

set the

appropriate

SOURCE switch to

EXT

.

Turn

on the instrument with the POWER switch on the front

panel of the Power Supply Unit

and

allow a few minutes for

the units to warm up. A time-delay relay

in

the Power Supply

Unit delays the operation

of

the instrument for approximately

45 seconds after the

power

switch

is

turned on.

This

delay

allows the tubes sufficient time

to

heat

before the

de

oper-

ating voltages

are

applied.

If the

ac

power

is

interrupted

for

an

instant, the normal 45-second

delay

will occur before

the de power

is

restored.

Using the beam-position neons

as

a guide, position the

free-running traces on the crt screen, then adjust the

INTEN

-

SITY

control for a trace

of

adequate

intensity.

Rotate the

LEVEL

controls to trigger

the

two displays.

If

the triggering signal ·

is

small or of high frequency, the

VER-

NIER

control may

be

adjusted for the most stable triggering.

Position the traces with the

HORIZ.

POSITION controls

so

they start

at

the left

edge

of the graticule,

and

adjust

the

FOCUS controls for the sharpest possible focus.

Use

of

SX

Magnification

The HORIZ.

DISPLAY

switch

of

either

beam

provides

selection of five times magnification

of

the signal displayed

on that

beam,

using either time-base

generator

to

drive the

sweep.

To

magnify the display, move the HORIZ.

DISPLAY

switch from the

X1

position to the

X.2

position. The center

2

em

of the display with the switch

on

the

X1

position

is

then

expanded

to cover the entire 10

em

of

the crt screen

(see

Fig.

2-7). Any 2-cm portion of the original display, now

expanded,

can

be

positioned on the crt screen with the

appropriate

HORIZ

. POSITION control.

The sweep

rate

of the magnified display

is

five times

that

indicated by the TIME/CM switch. The true

sweep

time

per

centimeter

of

the magnified

sweep

is

found by multiplying

the reading of the TIME/CM switch by 0.2,

or

by dividing

by five.

If sweep magnification

greater

than

5X

is

required, use

the

delayed

sweep magnification

mode

described later

in

this section.

Use

of

Horiz. Position Controls

The two beams

have

independent horizontal positioning.

The Upper Beam

HORIZ.

POSITION control positions

the

Upper Beam display; the Lower Beam HORIZ. POSITION

2-8

control positions the Lower Beam display. Clockwise rota-

tion

of

either control causes the

trace

of

the particular

beam

to move

to

the right

on

the crt screen,

and

counterclockwise

rotation moves the

trace

to

the left.

When

the HORIZ.

DIS-

PLAY

switch

is

set for

5X

magnification

(X.2),

the HORIZ.

POSITION control provides sufficient

range

to view

any

portion

of

the

expanded

display.

Each HORIZ. POSITION front-panel knob

operates

both

coarse

and

fine adjustment

of

the positioning by means

of

a

backlash coupling

between

the controls inside the unit. To

position the

trace

horizontally, turn the HORIZ. POSITION

control slightly

past

where

you

want

it,

then move

it

back

to the desired final position. The fine adjustment control only

operates

in

the backlash

of

the

coarse

adjustment control.

For

example, to move the

trace

to

the

right, turn the HORIZ.

POSITION control clockwise for the

coarse

adjustment until

the

trace

position

is

about

2

mm

past

the desired location,

then turn the control slightly counterclockwise for fine

ad-

justment

of

the

trace

position.

HORIZ.

DISPLAY

X.2

•

Unmagnified

xo

HORIZ.

DISPLAY

X.

2

XoM•

.,

......

1-

-

I--

----

1-

,

Fig.

2-7

.

Operation

of

the

SX

swHp

magnification.

OPERATING

MODES

----

1-

-

~:..

-

The Type 555 Oscilloscope provides many modes

of

sweep

operation,

making the instrument

adaptable

to

a variety

of

applications. The normal triggered mode,

in

which the

sweep

is

started

by a signal

that

is

time-related to the

displayed

input signal,

is

the most common

sweep

mode.

Operation

of

both time-base units

is

the same

except

for the

Delayed

Sweep modes.

Triggered

Sweep

Set

the

SWEEP

FUNCTION switch

to

either NORMAL

or

AUTO

BASELINE

for normal triggered

operation

. Trigger the

display with the

LEVEL

and

VERNIER

controls

as

described

previously. (AUTO

BASELINE

in

the Type

21

A

and

Type 22A

is

a

sweep

mode with automatic baseline, rather

than

the

low-frequency automatic triggering

mode

found

in

many

Tektronix oscilloscopes.) For triggering rates

above

20

cps,

triggering

is

the

same

in

either

NORMAL

or

AUTO

BASE-

LINE..

In

addition,

AUTO

BASELINE

provides a free-running

baselme

trace

when

no triggers

are

applied.

For triggering

rates

below

20 cps, use NORMAL position

of

the SWEEP

~UNCTION

switch, since AUTO

BASELINE

will

produce

an

mterm1ttent free-running

baseline

in

this frequency

range

.

With

the

SWEEP FUNCTION switch

at

NORMAL the

swe:p

is

held off until a

trigger

of

the

proper

amplitu,de

is

rece1ved. After the

beam

has

swept

and

retraced,

it

waits

for the next triggering pulse, then

begins

when the

trigger

pulse

reaches

the

selected

triggering level.

With

the

swit~h

set

to

AUTO

BASELINE

and

the triggering

~ontrol

set

for tngge_red

operation,

the

sweep

is

free running

I~

the

absence

of

tnggers.

When

a

trigger

is

received, the

T1me-Base

Generator

stops free running. Then,

if

another

trigger pulse

is

received within 1

/20th

of

a

second

a normal

triggered

sweep

of

the

trace

will occur (if the

swe:p

is

ready

to

be

triggered). However,

if

no trigger pulse arrives within

1

/20th

of

a

second,

the

auto

baseline circuit will

again

cause

the Time-Base

Generator

to

free run until

another

trigger

pulse

is

received.

Free

Run

To

free run the

sweep,

set

the SWEEP FUNCTION switch

on the time-base plug-in unit

to

AUTO

BASELINE

and

turn

the

LEVEL

control

either

fully clockwise

or

fully counterclock-

wise.

In

AUTO

BASELINE,

with no triggering signal

applied,

the

sweep

will free run

in

nearly

any

position of the

LEVEL

control,

however

random

triggering will

occur

on stray noise

signals

when

the control

is

set

at

the

zero

triggering level,

causing intermittent free run

operation

. Therefore

it

is

recom-

mended

that

the

LEVEL

control

be

set

at

either

end

of

its

range. This will

also

allow

a signal

display

to

free run

when

the

trigger

amplitude

is

less than 10 volts. If you desire

to

free run the

sweep

in

the

presence of a

large

input signal,

set the SOURCE switch

to

some position receiving no input

triggers (e.g.

EXT.).

A free-running

sweep

is

convenient for locating

and

posi-

tioning the crt

beam

while no input signal

is

applied

.

It

also

can

be

used

to

establish a reference

voltage

level for making

de measurements.

With a free-running

sweep,

one

of

the

time-base

genera-

tors

can

initiate the input signal by using the

+Gate

or

Sawtooth

output

waveform

to

trigger

or

drive a device

under

test. The response

waveform

will then

be

synchronized with

the

sweep

repetition

rate

of

the

time-base

generator

and

will

present a

stable

waveform

on

the

crt. Set the TIME/CM

switch

and

VARIABLE

control

to

produce

the desired repeti-

tion

rate

.

(This

may

be

observed

by monitoring the

output

waveform with the

other

time-base unit.)

To

display

one

cycle of the response

waveform

, drive the

crt

beam

with the time-base unit

that

is

generating

the out-

put

+

Gate

or

Sawtooth waveform.

Fig

. 2-8 illustrates this

mode

of

operation

with Time Base B

and

the Lower Beam.

To

display more than

one

cycle

or

a portion of the

wave-

form, set

the

HORIZ.

DISPLAY

switch

to

the

second

time-

base

unit for driving the crt

beam

. Set the controls

of

the

second time-base unit for

triggered

operation.

To

display both the

output

waveform

and

the response

from the external device,

apply

the

output

signal

to

one

vertical INPUT

and

the response signal

to

the

other

INPUT.

®

Operating

Instructions-

Type

555/21A/22A

Fig.

2-8.

Using

th"

+GATE

or

SAWTOOTH

waveform

to

trigger

or

drive

external

equipm

..

nt.

sw

..

ep

is

usually

free

running

.

The

two

beams

will then display

the

waveforms simultane-

ously. Similarly,

two

or more response signals from the de-

vice

under

test

may

be

displayed

together

through use of

the

two

beams

and

multi-trace plug-in units.

Delayed

sweep

pulse

generation

is

discussed

later

in

this

section of

the

manual.

Single Sweep

Single

sweep

mode

is

used primarily for viewing

or

photo

-

graphing

a portion

of

an

input

waveform

that

is

not repeti-

tive

or

that

varies

in

amplitude

or

shape.

To

display

a

triggered

single

sweep

of the crt presenta-

tion, first

set

up

the

triggering controls with the

SWEEP

FUNCTION switch

set

to

NORMAL

or

AUTO

BASELINE,

then move the switch to SINGLE SWEEP. Press

the

PUSH

TO

RESET

button

and

release

it

.

If

no trigger

is

received

immediately, the

READY

lamp inside the

PUSH

TO

RESET

button will light, indicating the time-base circuit

is

ready

to

be

triggered

. Then, when o trigger arrives, the crt

beam

will

sweep

once, the

READY

lamp will turn off,

and

the

sweep

will

be

held off until the

PUSH

TO

RESET

button

is

again

pressed

and

released

.

Single

sweep

s wili not occur without a triggering signal

ex

cept

by turning the

LEVEL

contrd through the normal

triggering level.

To

produce

single

sweeps

without

an

input

signal, the SOURCE switch

may

be

se

t to

LINE

position

and

the

LEVEL

control

adjusted

for line triggering. Then the single

sweep

circuit

is

armed

as

the

PUSH

TO

RESET

button

is

pressed

and

a

sweep

of the

trace

occurs

as

the button

is

released

.

In

addition

to

its usual function

in

single-sweep mode, the

PUSH

TO

RESET

button may also

be

used to cut off the

sweep

when

the

instrument

is

operating

normally

in

one

of the trig-

2-9

Operating

Instructions-

Type

555/21A/22A

gered

or

free-run modes. Whenever the button

is

pressed

and

held in, the sweep cannot

be

triggered

and

will

not free run.

Normal operation

is

restored when the button

is

released.

Delayed Sweep

the

TRIGGERABLE

ONCE

FOR

EACH

'A'

DLY'D

TRIG

posi-

tion, the Time Base B sweep

is

triggerable

at

the

end

of

the

delay

period,

and

will sweep

as

soon

as

a pulse

is

received

from the Time Base B Trigger circuit. These two modes

are

illustrated

in

Fig

. 2-9.

The Delayed Trigger pulse which occurs during

each

sweep

of 'A' Time-Base

Generator

is

applied to the 'B' Time-Base

Generator

as

well

as

to

the

DELA

YEO

TRIG.

OUT connector.

This

Delayed Trigger from Time Base A can be used to hold

off the triggering or sweep of Time Base B for a certain

selected period after the

Time

Base A sweep has started.

The delay time

is

continuously variable from .05 p.sec to 50

seconds. When the Time Base B

SWEEP

FUNCTION switch

is

in

the

SWEEPS

ONCE

FOR

EACH

'A'

DLY'D

TRIG

position,

the Time Base B sweep occurs immediately

at

the

end

of

the delay period.

When

the

SWEEP

FUNCTION switch

is

in

Operation

of the

delayed

trigger

and

delayed

sweep

magnification

are

described

in

the following paragraphs.

Use of the

delayed

sweep for making time measurements

is

given

in

the Applications section

of

this manual.

MODE

1:

SWEEPS

ONCE

FOR

EACH

'A'

DLY'D

TRIG

a.

Delayed

Trigger

To

use the Delayed Trigger pulses for triggering

an

exter-

nal device connect a

cable

from the

DELA

YEO

TRIG

. OUT

connector to the device under test

and

connect the response

signal to the

INPUT

of either vertical plug-in unit. Set the

~~.·

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

~

'A'

Sweep

runs

v-'1

I

'A' Trigger

pulse

Delay time

(Variable from

0.1 t<sec

to

SO

secl

'A'

Dly'd

trigger

starts

'B'

sweep

I

'READY'

light

may

go

on

i

I

f\.-JLJL.J\.:-_fL~~-

J

LILJL.JLJL.l

A

Sweep

presentahon

_______

.J

Brightened portion l

__

,,----------------------------------

of

waveform

------------------------,

:

1\

1\. 1\.

r

'

B'

Sweep

presentation

MODE 2:

TRIGGERABLE

ONCE

FOR

EACH

'A'

DLY'D

TRIG

Kl

l

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

I

~::

'A'

Sweep

runs

v"'"l

'A' Trigger

p~lse

'A'

Dly'd

trigger

t

arms

'

B'

trigger

lr<

:

----------~~--------~~~:

. Delay time

L/'1

(Variable.from 1

I 0 1 t

so

1

'READY'

light

1 • t<sec o sec

I

goes

on

I

'

B'

Sweep

is

triggered

I

: I

I I

.t\-JLJL.~L

J

LJLJL--~LL'L

.

.'U

A

Sweep

presentatoon

-----------

Brightened portion

'----

'

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

of

waveform

------,

/-------------------- -------------

1\.

1\

....

~

~----------1\.

1\.

I

'B'

Sweep

presentation

Fig.

2-9.

Comparison

of

the

two

delayed-sweep

modes.

In

each

case

the

'A'

presentation

represents

tho

Input

to

both

vertical systems Tho

in-

tensified portion

of

tho

'A'

presentation

shows

the

part

of

the

Input

waveform

that

is

displayed

in tho 'II'

presentation.

•

2-10

®I

Tektronix 555/22A User manual

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