Dynascan corporation E410c User manual

SWEEP GENERATOR MODEL

AND

MARKER ADDER E410C

I e

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PRECISION

APPARATUS

DIVISION

OF

DYNASCAN

CORPORATION

1801

W.

BELLE

PLAINE

AVE, • CHICAGO,.

ILL,.

60613

.4

80-07

s-~-oo,

2-67

COPYAtGHT

C...19(.7

,f

•

-

..

i

,.

'

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..

:

·.

' .

►

:

'

◄

'

..

.........

'

◄

'

-'

'

FOR

PRECISION

APPA

Model E410C

Sweep

Generator

and

Marker Adder

PRECISION

APPARATUS

TUS

A DIVISION

OF

DYNASCAN

CORPORATION

1801

West

Belle

Plaine

Avenue

Chicago,

Illinois

60613

CONTENTS

Page-

Introduction

.......... .................. ...... .... .. ........... ........

I.

General

Specifications

.................................................

.

II.

Principles

of

Operation

of

thP

Model

E410C

Sweep

Generator

.............

.

3

5

III.

Model

E410C

Panel

Controls

and

Switches

................................

10

IV.

Front

Panel

Connectors

and

Cables

......................................

11

V.

Preliminary

Set

Up

Procedure

..........................................

12

VI.

Basic

Alignment

Procedure3

............................................

14

1.

F.M.

Receivers

.....................................................

14

A.

I.F.

Alignment

...................................................

14

B.

Discriminator

Alignmrnt

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

C.

Oscillator

Alignment

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

D.

Overall

Check

of

R.F.

and

I.F.

Stages

..............................

20

2.

Television

Receivers

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

A.

Alignment

of

Picture

(Video)

I.F.

Traps

..........................

21

B.

Video

I.F.

Transformers

..........................................

22

C.

Multiple

Marking

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

D.

Sound

Discriminators

............................................

27

E.

Sound

I.F.

Transformers

.........................................

27

F.

R.F.

Converter

and

Oscillator

Adjustment

. . . . . . . . . . . . . . . . . . . . . . . . . . 27

VII.

lntercarrier

Applications

...............................................

29

1.

Override

of A.G.C.

Bias

..............................................

29

2.

Alignment

of

I.F.

Transformers

......................................

29

3.

Alignment

of

Sound

Circuits

........................................

30

4.

R.F.

and

Convf.'rter

Alignment

.......................................

31

5.

R.F.

Oscillator

Alignment

...........................................

31

VIII.

SJ)ecial

Functions

and

Procedures

.......................................

35

I. I

ntrrnal

Marker

Oscillator

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

A.

Crystal

Calibration

of

Model

E200C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

B.

Crystal

Notes

...................................................

36

IX.

Special

Notes

. . .. . . . . .... ... . ...... .... .. . . . . . ........... .. . . ....... .. 37

X.

Service

Notf.'s .... . . . . . .. . ... . . .. .. ........ ... . . . .. . ... ............ . ...

41

'

•

'

INTRODUCTION

The

Precision

Apparatus

Model

E410C

T.

V.-F.

M.

Sweep

Generator

and

Marker

Adder

is a

wide

range

multi-purpose

frequency

modulated

signal

source

specifically

de!-ligned for

alignment

and

servicing

of

T.

V.,

F.

M.

and

other

high

frequency

wide

band

receivers

and

circuits.

All

phases

of

its

design

have

been

coordinated

b,v

Precision

engineers

with

the

latest

developments

in

T.V.

and

F.M.

circuit

design,

so

that

the

E410C

provides

utmost

flexibility

and

simplicity

of

operation.

Unusual

flexibility of

marker

injection

frequencies

has

been

accomJllished by

use

of

an

internal

crystal

marker

oscillator,

(with

a 4.5

M.C.

crystal

supplied

with

the

E410C)

Jllus

provision

for

injection

of

an

external

variable

markPr

generator

.such

as

the

Prl'-

ci-=.ion

Apparatus

Model

E200C

Marker

Gene-.-ator

"ll

niixerl clectron!cal/31

11•ith

the

sweep

generator

output

in

the

internal

marker

arl<ler

section

of

the

E410C.

This

featurr

Jlermits

the

viewing

of

markers

in

traps

and

along

the

line.,,.

portion

of

the

discriminator

"S"

curve

without

distortion

of

the

oscilloscope

pattern

duP

to

overloading

of

the

I.F.

stages

of

the

receiver

under

test.

Intelligent

coordinated

use

of

the

Model

E410C

T.

V.-F.

M.

Sweep

Generator

and

Marker

Adder,

will

reveal

to

the

user

its

unusual

featurPs

and

flexibility of OJJeration

in

keeping

with

the

established

Precision

Apparatus

reputation

for

"The

Hallmark

of

Quality

in

test

equipment".

I.

GENER.4.L SPECIFICATIONS

I.

FREQUENCY

COVERAGE:-

Band

A: 3-7

MC

Band

B:

6-14

MC

Band

C: 13-33

MC

Band

D:

35-85

MC

Band

E:

80-216

MC

Band

E,.: 400-1080

MC

Bands

ABCDE

are

fundamental

frequencies.

2. A 5"

no

glare

aluminum

tuning

dial,

engine

turned

finish,

with

approximately

5

feet

of

easy

reading,

2 color

deeply

etched

scales.

The

V.H.F.

channels

(2-13)

are

calibrate-d on

the

tuning

dial.

3.

Sweep

width

continually

variable,

ranging

from

0-3

M.

C.

on

band

A

to

0-30

M.

C.

on

band

D.

On

band

E

the

sweep

width

is

variable

from

0-16

M.C.

4.

Marker

adder.

A

special

feature

of

the

E410C

with

circuitry

designed

to

avoid

overloading

of

receiver

circuits

when

inserting

markers.

This

is

accomplished

by

superimposing

the

marker

on

the

receiver

response

in

the

E410C,

not

in

the

receiver

under

test.

As a

result,

markers

are

visible

in

traps

and

on

discriminator

"S"

curves.

Front

panel

controls

for

the

marker

adder

section

of

the

E410C

permits

control

of

marker

width

and

marker

amplitude

independent

of

the

pattern

size

on

the

scope

trace.

Injection

of

the

marker

signal

at

the

vertical

inJJut of oscillo-

scope

(post

injection)

eliminates

spurious

markers

on

the

scopf' rPSponse

curve

display.

5.

Output

impedance

50

ohm

terminated.

3

6.

Internal

blanking

is

accomplished

by

dual

circuits,

automatically

eliminating

the

return

trace.

7.

Automatic

gain

control

regulates

the

R.F.

voltage

amplitude

on

anv

one

band

so

that

the

output

is

effectively

flat

over

the

entire

band.

~

8.

Fixed

frequency

markers

provided

by

crystal

03ci1lator

circuitry,

with

the

crystal

socket

on

the

front

panel.

Either

the

4.5

M.

C.

crystal

supplied

with

the

E410C

(or

other

crystals)

can

be

inserted

to

provide

accurate

marker

''pips''.

9.

External

,narker

input

connector

pemits

use

of

an

external

R.

F.

generator.

such

as

the

Precision

Apparatus

Model

E200C

to

provide

variable

frequencv

marker

'•pips"

on

the

scope

trace.

~

10.

An

inter1~al ph'lSing

control

corrects

phase

shift

between

the

R.

F.

output

and

scope

horizontal

output

and

compensates

for

phase

shift

in

the

horizontal

amplifier

of

the

oscilloscope

itself.

11.

Complete

shielding

of

the

R.F.

oscillator

section

of

the

E410C

through

the

use

of

copp~r

plated

shielding

of

all

oscillator

circuitry

as

well

as

a

copper

plated

main

chassis.

12.

Separate

line

filter

with

shielded

line

cord

assures

minimum

radiation

from

line

cord.

13.

Telephone

type

cabled

wiring

using

highest

quality

plastic

insulation.

14. 5 cables

provided,

as

follows:

a.

R.F.

cable

(50

ohm

termination)

b.

Oscilloscope

vertical

output

cable

c.

Oscilloscope

horizontal

output

cable

d.

Marker

generator

input

cable

e.

Receiver

response

input

cable

15. Contin.uously z,ari.able

attenuators

are

provided

to

control

sweep

width,

and

vertical

~ope

pattern.

A

dual

attenuator

system

provides

coarse

R. F.

output

attenuation

1n

three

20

D.

B.

steps

and

a fine

continuously

variable

control

within

each

20

D.

B.

step

for

the

R.

F.

output.

16.

Tube

and

diode

compliment.

V-1

6BQ7A

Sweep

oscillator

and

cathode

follower

V-2

6BY8

Blanking

and

second

AGC

amplifier

V-3

12AX7

First

AGC

amplifier

and

crystal

marker

oscillator

V-4

12B4

AGC

and

blanking

series

regulator

V-5

6X4

Rectifier

V-6

6CB6

Sweep

sampling

amplifier

V-7

12AX7

Marker

adder

amplifier

IN87

Marker-sweep

mixer

65MA

Rectifier

•

bias

rectifier

4

17.

Power

requirement

18.

General

specifications

Dimensions

Shipping

weight

117

volts

50-60

cycles

13 x 8

1/2

x 7

inches

15

pounds

II. PRINCIPLES OF OPERATION OF THE MODEL

E410C

SWEEP GENERATOR

The

primary

function

of a

swee1>

generator

is

to

provide

the

means

for

obtaining

on

the

screen

of a

cathode

ray

oscilloscope. a

PICTURE

Clf a

circuit

response

curve.

The

standard

A.M.

method

of

PEAKING

a

tuned

stage

(such

as

an

I.F.

stage)

by

means

oI

an

A.M.

signal

generator

and

V.T.V.M.

is

not

adrquatP

in

the

case

of

F.M.

and

T.V.

since

response

of

the

tunEd

stage

must

be

adjusted

NOT

ONLY

AT

THE

MID-

POINT

of

thr

response

curve

but

at

t)tht~r

points

ALONG

the

response

curve.

The

on!y

rapid

and

convenient

means

of

adjusting

the

OVERALL

shape

of a

very

broad

curve

is

to

OBSERVE

THE

PICTURE

of

the

wave~shape

on

an

oscilloscope

screen

and

simultaneously

adjust

the

response

of

the

tuned

circuits involved.

So

that

the

technician

is

aware

of

exactly

HOW

a

response

curve

is

obtained

on

an

oscilloscope

and

what

the

response

curve

represents.

the

following

explanation

is

•

given:

I.

Reference

to

Fig.

1

indicates

the

normal

operation

of

the

usual

ty11e

oscilloscope

before

external

potentials

are

applied

to

the

VERTICAL

the

oscill()scope.

cathode

rav

•

amJJlifier of

The

internal

horizontal

sweep

system

of

the

oscilloscope

is

sweeping

the

electron

beam

back

and

forth

horizontally

(at

a

rate

determined

by

the

horizontal

fre•

quency

control

of

the

oscilloscope)

creating

the

picture

of

a

straight

horizontal

line.

NO

VERTICAL

INPUT

VOl.TAGE

RETURN

TRACE

-

---

:,

r----

..,.

____

_

0$ClLLOGRAPI-I ALONE -HORIZONT~L

S~EEP

MOVES BEAM

BAC:K

Bi

roRTH

60

TIMES

PER SECONO

ILLUSTRATIVE

BEAM

MOVEMENT

Fig. 1

ACTUAL

VISUAL

RESULT

2.

As

the

output

of

the

E410C

is aJJplied

to

a 10.7

megacycle

F.M.~I.F.

system

(for

example)

an

R.F.

signal.

varying

or

"sweeping''

from

10.775

MC

to

10.625

MC.

60

times

per

second,

is

transmitted

through

the

I.F.

system.

5

The-

latter

1>oint

is im1>ortant

since

it

means

that

all

voltages

from

F.M.

limiter

stages.

video

second

detector

stages,

etc.,

which

will

be

connect.ed

to

the

vertical

ter-

minals

of

th{•

o.-;cillosc(>pe

in

the

usual

F.M.

and

T.V.

alignment

procedure

(using

a

SweeJJ

Generator),

will he low

in

frequency

and

therefore

the

use

of

the

standard

type

of

cathode

ray

oscilloscope

with

high vertical

sensitivity

such

as

Precision

Apparatus

ESfi50B

or

S-fi5 is

all

that

is

necessary.

The

I.I<".

system

has

a

frequency

response

characteristic

which

will

appear

as

noted

in

Fig.

2.

The, shaJJP of

this

characteristic

indicates

that

a

signal

at

exactly

10.70

MC

will be

passed

at

maximum

amplitude

(Point

"X",

Fig.

2).

A

signal

of 10.75

MC

will

he

attenuat(,d

some-what. wl1ile a

signal

at

10.5

MC

will be

practically

completely

attenuated,

t'tc.

Th('re[ore

the

t(>tal

bandwidth

of

the

I.F.

response

curve

is

"swept"

through

by

an

applied

R.F.

signal

whose

frequency

is

being

shifted.

The

I.F.

system

will

J>ass

this

sig11al

at

magnitudes

!Jroportional

to

the

shape

of

its

response

curve.

This

I.F.

signal

(high

frequency

A.C.,

varying

in

amplitude

60

times

per

second

by

virtue

of

the

60

cycle

sweep

rate

of

the

E410C)

is

usually

taken

from

a

limiter

stage

in

an

F.M.

receiver

(or

the

video

detector

stage

in

a

T.V.

receiver).

In

order

to

drive

the

vertical

amplifiers

of

the

oscilloscope,

this

range

of

I.F.

fre-

quencies

(whose

amplitudes

are

varying

60

times

per

second

in

accordance

with

the

I.F.

response

curve)

must

be

rectified.

In

a

video

detector,

such

rectification

takes

place

across

the

video

detector

load

resistor

in

a

TV

receiver.

In

an

F.M.

receiver

the

receiver

response

input

cable

of

the

E4IOC

is

connected

across

the

limiter

grid

resistor

(points

"W"

and

"GND"

Fig.

3).

This

point

provides

a

varying

low

frequency

voltage

because

the

magnitude

of

voltage

developed

across

the

limiter

or

detector

load

resistors

"follows"

the

amplitude

of

the

signal

impressed

upon

their

circuits.

This

"response

voltage"

after

passing

through

the

marker

adder

circuits

is

fed

to

the

vertical

input

of

the

oscilloscope

and

causes

the

beam

of

the

oscilloscope

cathode

ray

tube

to

travel

up

and

down

60

times

per

second.

Without

any

horizontal

deflection

of

the

beam,

the

picture

on

the

screen

of

the

oscilloscope

would

be a

vertical

straight

line.

If,

however, a

voltage

varying

60

times

per

second

(as

is

provided

by

the

E410C)

is

applied

to

the

horizontal

deflecting

system

of

the

oscilloscope,

the

beam

would

then

be

deflected

horizontally

at

the

same

rate

it

is

being

deflected

vertically.

This

results

in

a

spread-out-pattern,

reproducing

the

response

characteristics

of

the

receiver

I.F.

amplifier

system.

TYPICAL

RESPONSE

CURVE

OF A

TUNED

CIRCUIT

j -100

KC

FROM

l._+100

KC

FROM I

l°RESONANT FREQ. RESONANT FREa"\ 0

-

10.8 -

-

-10.75

MAX. AMPLITUDE 5

OF

SIGNAL -

-

-10

"x"

I0.7MC

Fig. 2

6

•

TO

IF

STAGES

RECEIVER

RESPONSE

CONNECTOR

E410C

=

,, .,

RED

W

ALLIGATOR

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-

Figure

4

illustrates

in

hlock

form,

the

circuitry

that

produces

the

swept

R.F.

signal

which

is

injected

into

the

receiver

tuner

circuits,

and

the

Marker

Adder

circuitry

which

feeds

the

rectified

receiver

"response

voltage"

and

the

demodulated

crystal

and/or

external

marker

"pips"

to

the

vertical

input

of

the

oscilloscope.

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,r

VERTICAL

PATT,

•

The

Colpitts

type

variable

frequency

modulated

oscillator

uses

one-half

of

the

6BQ7

A

tuhe

(VIB),

which

covers

a

fundamental

range

of 3

to

216

M.C.

in

five

bands

and

400-1080

MC

on

harmonics.

The

oscillator

coils

are

built

into

the

Increductor

unit

and

are

connected

in

series

with

taps

brought

out

to

the

variable

tuning

condenser

and

the

band

switch.

All coils

are

in

the-

circuit

in

the

lowest

band,

and

are

progressively

shorted

out

as

the

switch

is

rotated

to

the

higher

bands.

In

the

highest

band,

the

coil

consists

of

the

copper

strip

of

the

Increductor

and

the

contacts

of

the

switch.

The

coil

cores

are

made

of a

special

ferrous

compos!tion,

and

arc

located

between

.

and

make-

contact

with,

the

laminated

pole

pieces

of

the

inductor

core. A

control

winding

around

the

inductor

core

controls

the

magnetic

flux

density

of

the

oscillator

coils

and

inductor

cores.

When

current

passes

through

the

control

winding,

the

perme-

abilities

of

the

special

core

materials

are

reduced.

This

causes

a

decrease

in

inductance

of

the

ocillator

coils.

The

center

frequency,

which

is

marked

on

the

dial,

occurs

when

the

current

flow

in

the

winding

is

half

way

between

zero

and

maximum

current.

The

maximum

deviation

below

this

center

frequency

occurs

at

zero

current

flow,

and

the

maximum

deviation

7

above

this

center

frequency

occurs

at

maximum

current

flow.

Center

frequency

sweep

is

further

controlled

by

the

use

of

a

D.C.

bias

current

through

the

control

winding

which

is

used

to

calibrate

the

lower

frequency

bands

of

the

E410C.

The

magnitude

of

the

inductor

cont!."ol

current,

which

sets

the

over-all

sweep

width

(over-all

frequency

variation)

is

controlled

by

a

front

panel

potentiometer

(R20)

in

series

with

a

limiting

resistor

(R21)

to

prevent

overlo3ding

of

the

controllable

inductor

across

the

117 volt

line.

The

Increductor

unit

is

connected

to

one

end

and

the

arm

of

R20

through

a

hlocking

caJJacitor

(C33).

Capacitor

C15,

in

parallel

with

the

inductor,

is

chosen

to

resonate

with

the

inductor

at

60

cycles

and

thus

increase

the

range

of

sweep

current

and

range

of

sweep

width.

The

D.C.

voltage

which

develops

the

bias

current

is

obtained

by

rectifying

(CRl)

and

filtering

(C32)

the

117

volt

60

CPS

line

voltage.

The

D.C.

bias

current

is con-

trolled

hy

series

resistors

Rl9,

RIB,

R17

which

are

selected

by

the

band

switch

so

that

at

zer<>

swt>eJ)

width,

the

operating

frequency

is

halfway

between

the

maximum

frequency

helow

and

ahove

the

OllPrating f,.equPncy

at

maximum

sweep,

insuring

excellent

sweep

linearity

on

all

hands.

Since

the

ranges

of

the

swept

oscillator

are

all

fundamental

in

frequency

except

Band

E,,

the

output

is ade::iu'.Jte

on

all

bands

for

all

receiver

alignment

and

servicing.

To

insure

a

linear

display

on

the

oscilloscope

screen

the

60

CPS

horizontal

voltage

fed

to

the

horizontal

scope

input

must

be

controllable

as

to

phase

and

must

have

mini-

mum

distortion.

R32

is

the

variable

phase

control

in

conjunction

with

C28

and

net-

work,

consisting

of

R33,

34, 35

and

C27

filters

and

attenuates

the

60

cycle

voltage

which

is

applied

to

the

horizontal

input

circuit

of

the

scope

through

the

E410C

horizontal

connector

and

cable.

To

insure

isolation

from

the

line

the

voltage

is

taken

from

the

secondary

winding

of

the

power

transformer.

Since

the

inductor

control

current

and

the

horizontal

scope

voltage

are

both

sine

waves

and

are

drrived

from

the

117

volt

line

the

sweep

display

on

the

scope

will

have

a

linear

variation

of

frequency

versus

horizontal

displacement

from

the

low

to

the

high

edge

at

the

swPpt

hand.

The

swept

RF

signal

from

thl:'

grid

of

Vlll

is

coupled

to

the

grid

of

the

second

half

of

the

6BQ7A

tube

(VIA)

which

is a

cathode

followPr.

Since

the

cathode

follower

has

a

high

input

impedance,

the

loading

effect

on

the

oscillator

is

minimizPd.

The

output

impedance

of

VIA

is

low

and

the

output

signal

from

this

tube

is

thus

coupled

to

the

low

impedance

attenuator

network

for

maximum

transfer

of

energy.

The

swept

RF

output

is

also

coupled

through

C13

to

the

grid

of

the

sweep

sampling

amplifier

6CB6

(VB).

This

tube

amplifies

the

sample

of

sweep

RF

voltage

obtained

from

the

sweep

generator

VIB

and

isolates

the

sweep

generator

from

the

marker

adder.

It

is

shielded

and

thoroughly

decoupled

to inBure

maximum

isolation.

The

crystal

marker

oscillator

consists

of

one-half

of

the

12AX7

tube

(V3B).

When

a

suitable

crystal

is

inserted

into

the

front

panrl

crystal

socket,

crystal

accuracy-marker

and

calibrating

"pip"

will

aJJpear

on

the

scope

trace.

A 4.5

M.C.

crystal

is

supplied

with

the

E410C.

A

front

panel

connector

permits

use

of

an

external

marker

generator

such

as

Precision

Apparatus

Model

E200C

to

supply

additional

""pips"

at

variable

frequencies

on

the

oscilloscope

tracP.

The

output

of

the

sweep

sampling

amplifiPr,

the

crystal

marker

oscillator

and

the

external

marker

genc'rator,

are

injc•ctPcl int<l

the

1N87

germanium

diode

mixer

(SRl)

which

democlulates

the

developed

beat

frequC'ncies.

The

width

of

thP

marker

pulse

is

continuously

adjustahle

by

use

of

the

MarkPr

Wiclth

Control

R42

which

changes

thC'

time

constant

of

the

filter

(R42

and

C21) locatP<l

in

the

grid

circuit

of

the

first

marker

adder

am1)lifier

(one

half

of

12AX7

[\'?A]).

Amplitude

of

the

marker

pulse

is contin11-

8

'

•

'

ously

adjustable

by

use

of

the

Marker

Size

control

R44

in

th:>

grid

circuit

of

the

second

marker

adder

amplifier

(1

/2

of

12AX7

[V7B]),

which

h<>lps

to

isolate

the

i:narker

pulse

from

the

output

circuit

of

the

receiver

under

test

to

IJrevent

possibility

of

interaction

between

the

receiver

output

ancl

the

marker

pulse.

The

out11ut

"responsr

voltage"

of

the

receiver

is fed

through

the

receivc,r

response

cnhle,

and

the

recPiver

responsP

connector

on

the

E410C

to

the

top

of

the

pattern

amplitude

control

R47,

which

pPrrnits

continuouslv

variahle

control

of

the

reeeiver

response

pattern.

The

signal

from

the

output

of

the

second

mark.er adcl(•r

amplifier

and

the

signal

from

the

arm

of

the

Pattern

amJJlitude

control

are

f<>d

to

the

scope

vertical

connector

on

the

E410C

Panel.

This

comhined

signal

is

fed

to thP

vertical

input

connector

on

the

scopr

through

the

scot>P

vertical

cahle.

The

swept

RF

output

is hlankr.>d

during

the

interval

that

the

horizontal

sWf'PP

on

the

scope

is

moving

the

heam

from

the

PXtreme

right

to

the

l'Xtreme lf,ft

side

of

the

oscilloscope

(return

trace

on

Figure

1).

If

this

is

not

done.

a

mirror

image

of

thP

forward

trace

would

be

superimposed

on

the

forward

trace

resulting

in

difficulty

in

intepreting

the

pattern.

This

important

hlanking

feature

is

accomplished

in

thP

Model

E410C

by

simultaneously

driving

the

oscillator

grid

highly

negative

and

eutting

off thP

B+

supply

to

the

Oscillator

plate'.

The

blanking

circuits

operate

as

follows:

The

plate

of

the

blanking

tuht>-(a

diode)

½ of

6BY8

(V2A)

and

the

grid

of

the

first

AGC

amplifier.

½ of

12AX7

(V3A).

are

tied

together

and

are

coupled

to

the

grid

of

the

oscillat<Jr

(VlB)

through

isolating

resistor

(R14).

AC

voltage

from

the

high

voltage

secondary

winding

is fed to

the

cathode'

of

the

hlanking

tube

(V2A)

through

a

voltage

divider

consisting

of

R22

and

R23.

As

long

as

the

AC

voltage

applied

to

the

cathodP

of

this

diode

is

positive

the

plate

is

negative

in

respect

to

the

cathode

and

there

will

be

no

plate

current.

When

the

voltage

at

the

cathode

is

negative

in

respect

to

the

plate,

the

tube

conducts

charging

the

470

/J./Jfd

condenser

highly

negative.

This

nega-

tive

voltage

coupled

to

the

grid

of

the

oscillator

tube

through

the

Rl4

resistor

Cltts off

the

oscillator

tuhe

\vhich

has

hef'n

operating

with

its

own

gricl

leak

l1ias onl~'. clerivecl

from

R13.

When

the

cathode

of

the

blanking

tube

ht•eomPs JiositivP

in

re~qJPCt

to

the

plate

the

negative

voltage

on

C

leaks

off

through

RI4

ancl

R13

ancl

the

o~cillator

func-

tions

again.

The

negative

voltage

on

C is

also

applied

to

the•

grid

of

(V3A),

the

first

AGC

amplifier.

A

highly

amplified

positive

pulse

appears

at

the

plate

of

V3A

and

is

coupled

to

the

grid

of

the

second

AGC

amplifier

(½ of

6BY8

[V2B]).

At

the

plate

of

V2B,

a

large

negative

pulse

will

appPar.

This

large

negative

pulse

is

directly

coup

IPd

to

the

grid

of

the

regulator

tube

V4

(1284)

cutting

the

tuhe

off.

Since

the

cathode

of

V4

is

tied

to

the

platP

of

the

oscillator

through

thC'

coil

windings

of

the

Increductor.

when

the

12B4 is

cut

off,

no

voltage

appears

at

the

plate

of

VI

B

and

the

oscillator

is

cut

off.

The

oscillator

is

therefore

cut

off

in

two

ways

during

the

hlanking

period.

At

the

times

when

the

oscillator

is OJJerating,

the

outJJUt of thP

oscillator

may

vary

as

the

tuning

caJJacitor

dial

is rotatP£1

from

one

end

to

the

other,

or

with

line

voltag-e

fluctuation.

Automatic

gain

control

of thP o,:;cillator

output

voltagf• 11rPvPnts

this

varia•

tion

as

follows.

The

negative

D.C.

voltage

rlPvelo11ecl

at

the•

oscillator

g-rid

is

coupled

to

the

control

grid

of

the

first

AGC

am11lifier. .'\s tl1e

amplitude

of

oscillation

inereasps

or

decreases

the

D.C.

voltage

on

the

grid

of

the

oscillator

increases

or

decreases

accord-

ingly.

Assume

that

the

instantaneous

R.F.

outJJut

voltage

has

inerPaserl.

ThP

nPgat.ive

D.C.

voltage

on

the

oscillator

grid

will increas(• resulting-

in

a

mor<>

negative

voltage

on

the

grid

of

the

first

AGC

amplifier

(VSA).

This

causes

a morC'

Jiositiv<>

voltage

on

thr

plate

of

V3A

which

is

coupled

to

the

gricl of the'

s<>cond

AGC, am11lifier

tuhe

(V2B)

resulting

in

a

more

negativr-

voltage

at

thP 11latP of

V2B.

This

amJJlified

negativP

voltage

is aJJJJlird

to

the

grid

of

the

series

rf'gulator

tube

V4

increasing

the

eITective

resistance

of V4.

This

results

in

decrease

of

the

11latP

voltage

to

thP

oscillator

tube

(VlB)

causing

a

decrease

in

the

output

of

the

oscillator.

A

drop

in

the

R.F.

output

9

will

result

in

a

decrease

in

the

effective

resistance

of V4 rP.sulting

in

an

increased

B+

voltage

to

the

oscillator

and

a

resulting

increase

in

H.F.

output.

The

AGC

level

control

(R26)

(

internal

control)

is

used

to

adjust

the

AGC

current

for

maximum

output

on

all

bands

with

minimum

amplitude

variation.

The

attenuator

network

consists

of a

low

impedance

3-step

20DB

per

step

coarse

attenuator

switch

and

a

continuously

variable

fine

output

control

which

varies

the

output

from

0

to

maximum

output

for

each

20DB

step.

The

coarse

attenuator

switch

is

termi-

nated

in

50

ohms

which

matches

the

termination

of

the

output.

cable.

The

output

cable

is

connected

to

the

front

panel

output

connector

which

is fed

from

the

coarse

attenuator

switch.

The

other

end

of

the

output

cable

is

connected

to

the

input

circuits

of

the

circuit

under

test. • •

A

6X4

full

wave

rectifier

tube.-.

(VS) is

used

in

the

power

supply,

and

the

DC

output

is well filterPd

hy

the

RC

filter

consisting

of

C12

and

R31.

Plate

voltage for

the

rectifier. tl1e

filament

voltages

for

all

tubes

as

well

as

voltage

for

the

phasing

and

blanking

circuits

is

supplied

by

power

transformer

Tl.

Ill.

MODEL

E410C

PANEL CON1,ROLS AND SWITCHES

1.

MAIN

TUNING

DIAL

AND

BAND

SELECTOR

SWITCH.

The

markings

"A",

"B",

'"C",

"D''.

"E"

and

"E:-."

c>n

thP

"Band

Selector"

switch

refer

to

the

corresponding

bands

on

the

main

tuning

dial.

2.

SWEEP

WIDTH

CONTROL.

Manipulation

of

the

''sweep

width"

control

varies

the

degree

to

which

the

variable

oscillator

(VlB)

is

deviatPd

from

its

mean

frequency.

When

the

control

is

rotated

fully

counter-clockwise

only

the

frequency

appearing

on

the

dial

under

the

red

mark

on

the

plastic

pointer

appears

at

the

output

connector.

When

the

knob

is

rotated

fully

clockwise

this

frequency

is

swept

from

1.5

MC

above

and

below

3MC

at

the

3MC

end

of

band

A to

+15

MC

at

90

MC

on

band

D.

On

band

E tht"

deviation

is

+S

MC

about

the

center

frequency.

3.

OUTPlJT

CONTROL.

The

200

ohm

Fine

Output

contrc>l of

the

E410C

is located

in

the

cathode

circuit

of

the

R.f,.

outJJut

cathode-follower

tube

(VIA).

In

the

maximum

counter-clockwise

position

c>f

the

eontrol

the

arm

of

the

control

is

at

grc>und

and

no

voltage

appears

at

the

input

rJf

the

coarst')

attenuator

switch.

At

maximum

clockwise

position,

the

maximum

voltage

fleve1oJJf•d

acr()SS

the

C()ntr,)l is

feel

to

the

inJJut

<.)n

the

coarse

attenuator

switch.

4.

COARSE

ATTENlTATOR

sw11~cH.

ThP

t'<JarsP

atte11uatc•r attt"11uatPs tht•

signal

as

follows:

in

the

xl

position

of

the

switch

thP

full outJJut

fr,>m

the

fine

output

C"(lntrol

is fed

t<J

the

output

connector

(lf

the

E410(-,.

In

th('

xl0

IJositicln thP

signal

is

attenuated

10

times

or

20DB.

In

the

xl00

JJositi<lil

tbt>

sig11aI is

attrnl1ated

another

20D8

and

in

the

xlOOO

position

the

signal

out-

lJut

()f

thP att<)nuat<)r is

1_

1

()00

of

the

voltage

in

the

xl

position.

The

output

f:'om

the

coarse

(>utJlUt

attPnuat()r

is fpd

trJ

the

output

connector

on

the

E410C.

Through

the

use

of

the

outJJt1t cl1hle thP

signal

is

coupled

to

the

input

of

the

circuit

under

test.

5.

MARKER

ADDER

CONTROLS.

Are

the

fr<)nt

1>2nel

controls

which

control

the

amplitude

of

the

response

pattern,

and

the

amJJlitufle

a11fl

width

cJf

the

external

or

internal

crystal

marker

'ipips''

in

the

marker

ad<ler sectil)n of

the

E410C.

In

swee{J gent:_•rators

without

the

marker

adder

fpature

it is

di~cult

to

obtain

~arge

marker

"piJJs''

without

,listorting

tl1e

receiver

responsp

curve.

Using

the

conventional

10

t

•

swt.)eJJ

g(>nerator,

since

both

thP

inJ>ut

circuit,

there

is a .st:rong

marker

genPrator.

marker

and

the

sweJ)t

R.

F. is

injected

into

the

receiver

possilJilitv

that

the

receiver will

bP

overloaded

bv

the

. .

In

the

E410C

the

markPr

is

added

to thf' recc-iver

re

1JJ(>·1Ge

pattern

aft~r

the

pattern

has

been

taken

fr(>m

thP rl'ceiver.

Tl1P

111ar!?er

is

never

inject.Pd

into

the

receiver.

The

marker

therefc>rt',

can

n(lVPr

m(Jdify thP receiver respon£;P

by

ovr•rloa<ling,

nor

in

turn

ean

thE'

markPr

Ile mtldifiP<l by

tbP

receivt.\r circuits.

l1'or

this

rt'asc)n.

with

tht• E410C

it

is JJossible

t:J

vie\v full

sL~ecl

marker

''J)ipsH

at

all

traJJ

Jl<1ints

ancl c)thPr zt•rt)-rea1>onse sectic>ns

c)f

rPspon3,:• curves,

such

as

at

the

zero

voltage

JJ<Jint

(}Il

a cli~c·rin1inator ••S'' curve.

a. Patter11 r11nJJlitl1(/e

l't111t

rol

cont;nuously

varies

the

amJJlitude of

thl'

tPst

receiver

rPSIH.lnSP

JJattPrr1

as

,lis1>1a.vf>r1

1J11

t}1e-

c>scill<JsC(>Jl!'

indt-'Jlendent of

tht>

marker

am1,litu(IP. 'l'ht•

:;51g11r1l

fr<>m

t.l1e

ret·Piver's vid~o

detector.

FM

detect<)r,

or

FM

limitPr is injt-cted int(J

the

receit

1

er

re~.nonr.;e

intJut C<Jnnector on tbP R410C

11:-,,r

mean--.

£lf

tht>

coaxial

cahlt>

1>r<Jvided.

The

signal

thPn

passes

tr,

thE•

tc>1>

c>f

tbe

JJattern amJJlitude

control.

The

arm

of

this

cclntrol is

connected

t()

the

scope

vertical

pan~l

connector.

Thrc>ugh

tht'

scoJJe

vertical

cable

tt1e

signal

is aJJplied

to

the

vertical

inJlut connectc>r of

the

oscilloscope.

In

the

full count~r-clockwise C(>ntrol. no

signal

v<>ltage

for

the

dE•tected

"receiver

response"

appears

at

the

input

to

thP scope.

At

full cl<)ckwise

rotation

the

full

output

voltage

of

the

dPtected

..rect"iver

response"

is

applied

to

the

input

of

the

scope.

b.

Marker

width

control

is

in

the

grid

circuit

of

the

first

Marker

adder

amplifier

(V7

A).

This

control

is

part

of

the

filter (R42.

C21).

With

thp

e<Jntrol set

to

maximum

counter-c1ockwise r1osition. the-

marker

is

of minim11m

width.

In

full

clockwise

position

the

marker

width

beC(lmes

maximum.

c.

The

marker

amplitude

control

in

the

grid

circuit

c>f

the

second

~1:arkPr

Ad<lc•r

amplifier

(V7B)

continuously

varies

the

vertical

siz~

(lf

the

marker.

In

the

extreme

counterclockwisP JJosition,

the

marker

will

not

appear

c1n

the

response

trace

on

the- oscilloscope.

In

the

maximum

clockwise

position

the

marker

will be

at

maximum

size.

The

marker

is fed

from

tht"

plate

of

V7B

to

the

scope

vertical

panel

connector

of thP

E410C

tc>gethPr

with

th~

receiver

signal

and

is ff'd

through

the

scope

VPrtica1

cahle

t<>

the

vertical

inr1ut

connectors

on

the

oscilloscope.

IV. FRONT PANEL CONNEC:TORS AND CABLES

1.

MARKER

INPUT

CONNECTOR

AND

CABLE.

The

marker

input

cable

connects

tht;,.

<lutput

of

a n1arker generat.c1r

t()

the

extern<1I

marker

input

front

panel

connectc>r

c>f

the

E410C. 1"his

cable

has

micr(>phone

typP

connectors

at

both

ends.

The

marker

input

connector

is

connected

to

the

1

N82

mixer

thr<lugh a

coupling

capacitclr C22.

2.

RECEIVER

RESPONSE

CONNECTOR

AND

CABLE.

The

receiver

resp<1nse

cable

connects

the

output

of

the

receiver

circuits

unclr•r

test

to

the

receiver

response

connector

on

the:,

E410C.

It

has

a

microphone

typt:• ct>nnector

on

one

end

and

a

set

of black

and

red

alligator

clips

on

the

other.

The

rPd

cli11

is

cc)n-

nected

to

the

high

side

of

the

output

take-off

and

the

l>lack

clip

to

ground.

The

micro-

phone

connector

end

goes

to

the

receiver

response

connector

on

the

E410C.

The

recei

ve,r

resJJonsf'

C<>nnectc>r

is

connected

to

the

to11

end

of

the

})attern

amplitude

ro11trol thr<>ugh

a filter

consisting

of

R47.

47K,

and

C26. 100

µ,µ,f.

11

3.

SCOPE

VERTICAL

CONNECTOR

AND

CABI.E.

'I'he

scope

vertical

cahle

connects

the

scope

vertical

connector

on

the

E4IOC

to

the

vertical

input

connector

of

the

scope.

The

microphone

connector

at

one

end

is

con-

n<'Cted

to

the

scope

V('rtical

connector.

The

red

banana

plug

at

the

other

end

is

conne~ted

to

the

vertical

input

connector

of

the

scope,

and

the

black

banana

plug

is

connected

to

the

grid

coni1ector

of

the

scoJ)e.

The

scope

vertical

connector

is

connected

to

the

J)late of

the

seco11d

marker

amplifier

throu~h

a 47 /tp.f cap::icitor

(C25)

and

through

a lOOK

isolating

resistor

R46

to

the

arm

of

the

lJattern

amplitude

control.

4.

SCOPE

HORIZONTAL

CONNECTOR

AND

CABLE.

The

sco1>e

horizontal

cable

is

similar

to

the

scoJle

vertical

cahle.

The

red

banana

p~ug

connPcts

to

the

s~u11e

horizontal

input

connector

and

the

hlack

banana

11lug

to

the

grid

connector

on

the

scope.

The

microphone

connector

connpcts

to

the

scope hori-

zontal

input

connector

o:i

the

E410C.

ThP

scope

horizontaJ

input

connector

is {'Onnected to

the

output

of

thp

60CPS

filter

and

att(•nuator

R33, R34,

R35

and

C27.

5.

OUTPUT

CONNECTOR

AND

CABLE.

'I'he

output

cable

is

similar

to

the

rece:ver

response

cable

except

that

it

is

terminated

with

a 47

ohm

resistor.

The

red

alligator

clip

is

connected

to

the

in11ut of

the

receiver

circuit

under

test

and

the

black

alligator

clip

is C(Jnnected to a

ground

point

as

close

to

the

input

as

possible.

The

other

end

of

the

cable

is

connected

to

the

output

connector.

The

outr1ut

connf'ctor

is conr1pcted

to

the

out11ut

of

the

co:i!se

attenuator.

This

cahle

can

hp

identified

hy

the

red

11!astic

insulation.

V. PRELII\IINi\RY SET-1:P PROCEDlJRE

Figure

5

illustrates

the

interconnection

set-up

between

the

required

test

instruments

and

the

receiver

to

he

aligned.

1.

The

output

cahlt>

connects

hetwe<>n

the

''RF

output"

connector

on

the

E410C

panel

ancl

thP

in11ut of

the

circuit

under

test.

This

is

the

cable

with

the

47

ohm

resistor

and

alligator

clips

at

one

end.

2.

The

out11ut of

the

circuit

under

test

connects,

hy

means

of

the

receiver-response

cable

to

the

receiver-responst'

connector

on

the

E410C.

This

cahle

has

alligator

clips

on

the

end

without

the

47

ohm

resistor.

3.

Tl1e

cahle

with

microphone

connectors

at

both

ends

is

connected

hetween

tl1e

high

R.F.

outJiut

connector

of a

variahlP

freqUPnc_v

marker

genprator

SU{'h

as

Precision

A1i1iarat11.-:

ModPI E20UC

and

the

marker

in11ut

connector

on

the

Maciel

E410C.

4.

1'hp

st·utH'

vertical

inJJUt

connector

on

the

E410C

is

connected

to

thP

vertical

input

t·onnet·torC'.>

of

an

os<'illo:,ct>JlP

such

as

Prt'Cision

Apparatus

ES550B

or

S-55

hy

means

of

<>ne

of

the

cahles

with

h3nana

J>lugs

at

on£>

encl.

The

red

hanana

plug

is

connected

to

th(' VPrtical in1)ut

connector

of

the

O!.{'illoseo1Je ancl

the

hlack

banana

J)lug

to

the

..

GND"

conneccor

on

the

scopP.

5.

'I'he

oscjJloscope

horizontal

inJJut

connector

on

the

E4

IOC is

connected

to

the

hori-

zontal

input

of the'

SCOJJP

throug-h

the

remaining

cable.

The

red

banana

plug

is

connected

tu

the-

horizontal

inJJUt

connPctor

of

the

scope

and

the

hlack

banana

plug

to

th0

"GND"

connector.

6.

The

controls,

switches,

etc.

of

the

Test

Instruments

should

be

set

as

follows:

12

•

A.

E410C

I.

Band

selector

switch

set

to

proper

frequency

band.

2.

Output

attenuator

switch

to

XIO.

3.

Fine

output

fully

counter-clockwise

.

4.

Pattern

a1nplitude

control

fully

counter-clockwise.

5.

Marker

a,nplitude

control

fully

counter-clockwise

.

6.

Marker

width

control

fully

counter-clockwise.

7.

Sweep

1vidth

control

fully

counter•clockwise.

8.

Power

on-ofl

switch

to

on

position.

B.

OSCILLOSCOPE

Manual

set•up,

1n

accordance

with

oscilloscope

instruction

manual,

with

the

following

exception:

"Sweep

Selector"

switch

(on

Precision

Apparatus

ES550B

or

S-55

to

EXT.

SW.

[external

sweep])

or

equivalent

settings

when

using

other

oscilloscopes

which

have

provision

for

use

of

external

sweep

voltages.

• MAR~ER CABLE

OSCILLOSCOPE

PRECISION

ES

5508

OR

S

55

•

-

-~-

--

-RECEIVER UN:T

UNDER TEST

I

AGC

DEFEAT

-

---ii

INPUT

C!RCUOT

'~L

-

--

OF

CIRCUIT

UNDER TEST

-.

AGC LEADS

._R[CEIV[R

I-SCOPE

I-

SCOPE

II,

OUTPUT CAB1.E INPUT

OF

OUTPUT

OF

RESPONSE

V[RTiCAL

HORl(ONTAL

TER"IINATEO

WITH C•RCUIT

CIRCUIT

CABLE

CABLE CABLE

47

OHM RESISTOR UNDER TEST UNDt'.A TEST

Fig.

5-Typical

sat•up

for

visual

alignment

with

Precision

Apparatus

E:ZOOC

Marker

Generator,

Precision

Apporatus

E410C

Sweep

Generotor

ond

Marker

Adder

andPrecision

Apparotus

ES550B

or

555 Oscilloscope.

.

IMPORTANT

NOTE:

In

view

of

considerahle

field

experience,

it

is

recom-

mended

that

the

EXT.

SW.

(or

equivalent

position

of

the

sweep-selector

switch)

be

used.

In

general,

the

use

of

saw-tooth

sweep

(as

derived

from

the

extenral

oscillator

generator

of

the

scope)

is

not

recommended

for

alignment

application,

because

of

the

difficulty

of

synchronizing

under

conditions

of

alignment

.

C.

VARIABLE

FREQUENCY

MARKER

GENERATOR

(such

as

Precision

Ap-

paratus

Model

E200C)

Normal

set-up,

using

the

generator

instruction

hook,

to

obtain

an

unmodu-

lated

R.F.

signal

of

the

required

frequency.

13

•o.

AGC

BIAS

DEFEAT

VOLTAGE

SUPPLY

The

AGC

jacks

on

the

E200C

provide

the

necessary

defeat

voltages

(up

to

50 volts)

where

this

is

required

by

manufacturer's

alignment

procedures.

*NOTE:

The

use

of

an

AGC

bias

defeat

voltage

is

required

in

the

alignment

of

certain

receivers.

When

this

11rocedurc> is

necessary

always

use

a

VTVM

to

check

the

actual

bias

defeat

voltagP.

VI. B1\SIC ALIGNMENT PROCEDURES

!.

F.M.

RECEIVERS

NOTE

1:

In

all

cases,

it

is im11ortant

that

the

operator

of

the

E410C

use

the

exact

procedure

for

alignmf'nt

sC't

forth

in

eitht•r

the

manufacturer's

service

manual

for

the

model

under

test

or

use

the

11rocc>durc

in

thr

service

manuals

for

the

exact

model

pub-

lished

hy

Sams

or

Rider.

In

the>

following

alignment

J>rol'('dures,

illustrations

of

typical

resJ)onsr

curves

will

be

noted.

The>

011erator

should

hPar

in

mind

that

thc>se

resJJonse

curve

illustration..-;

are

presentrd

as

generally

ty11ical of

the

type

of

eurvps

which

may

he

expectpd.

The

re-

sponse

patterns

which

will

hP

obtained

using

any

one

particular

F.M.

receiver,

may

differ

in

sha11c>

from

the>

illustrations

JJresented

in

this

manual.

The

operator

should

therefore

rPfPr

to

the

curve

illustations

J)rPsented by

the

spt

manufacturer

in

his

service

instructions

for

thP

exact

modPl

of

the

sPt

bring

aligned.

NOTE

2:

The

ground

(hlack)

alligator

clitJ

on

thP

E4IOC

output

cable

should

always

he

connected

or

cli1111ed

to

a

SJ)Ot

on

the

r('ceiver

chassis

as

close

as

possible

to

the

point

whPre

the•

red

(signal)

alligator

cliJ) is

connected.

NOTE

3:

In

the

following

11rocedures,

the

limiter-discriminator

type

of

F.M.

receiver

will

be

discussPd.

Procedures

for

aligning

ratio-detector,

locked-in

oscillator,

gated

beam

type,

and

others

use

the

same

alignmPnt

techniquPs

and

will

not

be

discussed

here.

The

manufacturer's

service

notes

will

cover

alignment

of

these

special

F.M.

detector

circuits.

The

hasic

alignment

steps

required

in

F.M.

receivers

are

as

follows:

A.

I.F.

alignment.

B.

F.M.

detector

alignment

(limiter-discriminator,

gated

beam,

locked-in

oscillator,

etc.)

C.

Oscillator

alignment.

D.

Overall

check

of

R.F.

and

I.F.

stages.

In

all

cases

refer

to

thP

manufacturer's

service

notes

for

alignment

procedures

and

wave

forms.

A.

I.F.

AI,IGNMENT.

The

over-all

rPs11onsP

curve

of a

typical

F.M.,

I.F.

system

is

indicated

in

Figure

6A.

For

the>

11urposes of

this

instruction

book, we will

assume

an

1.F.

response

curve

with

a

rPsonancr

11oint

at

10.7

MC

and

a 150

KC

width

along

the

"flat

top"

portion

of

the

curve

(75

KC

on

either

sirlP

of

the

center

frequenc)'

of 10.7

MC).

Fig. 6A Fig.

6B

14

•

The

over-all

response

curve

of

this

JJari..icular

I.F.

sy:;tt-m

may

he

11roduced

within

the

receiver

by

a

stagger

tunPd

system

or

by

individual

10.7

MC

"double

humped"

(

over-coupled)

stages

(as

illustratPd

in

FigurP

CB).

In

hotl1 casPs alignmc>nt is effected

by

"progressive"

adjustment

(similar

to

the

stan(lard

A.M.

mPth<ld).

This

is

done

by

injecting

the

signal

from

the

E410C

into

th{'

grid

of

the

I.F.

tub<'

nParest

the

limiter

or

discriminator

and

hy

indiv:dually

aligning

Pach stag:P

as

tl1t'

E410C

outJJut is

11ro-

gressively

connPctPd

to

each

I.F.

grid,

working

hack

t<)

thP

co11vPrtc>r

grid

.

TO

IF

STAGE

RECEIVER

RESPONSE

CABLE

FROM

E410C

II

w

II

GND

A

typical

application

is

as

follows:

LIMITER

DISCRIMINATOR

-

Fig. 7

1.

The

E410C,

oscilloscope,

and

external

variable

marker

is

set

u11

as

shown

in

Figure

5.

2.

The

red

alligator

clip

of

the

E410C

output

cable

is

connected

to

the

grid

of

the

I.F.

stage

nearest

the

limiter.

The

black

alligator

clip

is

connected

to

a

ground

point

as

close

to

the

grid

of

the

I.F.

tube

as

possible.

3.

The

red

alligator

clip

of

the

E410C

receiver

response

cable

is

connected

to

point

"W"

(top

side

of

the

limiter

grid

resistor),

and

the

black

alligator

clip

to

the

ground

side

of

the

limiter

grid

resistor.

(See

Figurf'

7.)

NOTE

1:

It

is

not

necessary

to

us<"

an

isolating

resistor

at

point

"W"

since

the

necessary

isolation

is accomJJ!ishecl

in

the

marker

adder

circuitry

of

the

E410C.

NOTE

2:

In

some

cases,

to

eliminate

interference

from

the

receiver

oscillator,

the

manufacturer's

instructions

call

for

the

removal

of

the

R.F.

oscillator

tube.

In

any

case

check

for

interf('r('nce

of

thr

local

R.F.

oscillator

by

rotating

the

tuning

dial

of

F.M.

receiver

whil<'

observing

th<'

oscilloscope

pattern

and

watch

for

distortion

of

the

response

curve

duP

to

the

presPnCf'

of

Pxtra

"pips".

With

all

other

connt>ctions,

controls

and

switchPs

set

up

in

accordance

with

Sec-

tion

V

(preliminary

set-up

procedure),

adjust

the

controls

of

the

E410C

as

follows:

a.

Set

thf' finp

output

control

to

maximum.

h.

8l't

tht•

eoarsP

attenuator

to

the

least

amount

of

signal

possiblP

to

get

a

receiver

respo11se <lisplay

curve.

Too

much

signal

will

overload

the

circuit

under

test

and

will

result

in

a

distorted

display.

15

c.

Set

the

hand

selector

switch

to

Band

B.

d.

Rotate

the

tuning

dial

so

that

the

I.F.

frequency

of 10.7

appears

under

the

thin

red

line

on

the

plastic

dial

indicator.

e.

Rotate

the

pattern

amplitude

and

sweep

width

control

about

half

way

in

a

clockwise

direction

until

a

response

curve

appears

on

the

screen

of

the

oscillo-

scope.

f.

Adjust

the

horizontal

gain

control

of

the

oscilloscope

so

that

the

width

of

the

trace

covers

about

3/5ths

of

the

screen.

If

the

response

curve

is

distorted,

reduce

the

R.F.

output

to

the

receiver

by

use

of

the

coarse

output

switch

and

fine

output

controls

until

an

undistorted

figure

similar

to

that

of

Fig.

6A,

B

appears

on

the

trace.

It

may

he

necessary

to

also

adjust

thP sweeJJ

width

and

pattern

amplitudP

controls

to

obtain

this

wave

shape.

If

a 10.7

MC

crystal

is

available,

insert

it

into

the

crystal

socket

of

the

E410C.

Slowly

rotate

the

marker

height

control

until

a

"pip"

appears

on

the

trace

as

shown

in

Figure

8.

The

width

of

the

"pip"

may

be

adjusted

by

rotation

of

the

marker

width

control.

Both

the

height

and

width

of

the

marker

"rJip"

should

be

such

so

that

details

of

the

trace

are

not

distorted

by

the

"pip".

In

some

cases

more

than

one

"pip"

or

marker

may

he

observed

on

the

response

curve.

In

order

to

observe

the

actual

crystal

"IJip",

rotate

the

marker

amplitude

control

fully

counter-clockwise.

The

crystal

"rJip"

(10.7

MC)

will

disappear

and

will

grow

larger

as

the

marker

amplitude

control

is

rotated

in

a

clockwise

direction,

while

the

extraneous

"pips"

will

rpmain

on

the

trace

unchanged

in

size.

Fig. 8 Fig. 9

The

I.F.

transformer

primary

ancl

secondary

should

not

be

adjusted.

until

the

"pip"

is

located

at

the

center

of

the

pattern

(Figure

9).

Before

attempting

the

(adjusting

the

shape

of

the

response

c.:urve),

refer

to

the

manufacturer's

instructions

for

the

recommendecl

sharJe

and

bandwidth

of

the

fJattern.

In

the

example

used

in

these

instructions

we

are

assuming

a

double

hump

type

of

curve

with

a 150

KC

over-all

bandwidth.

Unless

the

operator

has

available

two

additional

crystals,

one

75

KC

below

10.7

MC

and

one

75

KC

above

10.7

MC

he

should

use

his

standard

A.M.

generator

(such

as

the

Precision

Apparatus

E200C

as

a

variable

frequency

external

Marker

generator).

With

the

A.M.

generator

connected

as

shown

in

Figure

5

the

marker

input

cable

connected

bPtween

the

high

R.F.

connector

of

the

generator

and

the

marker

input

connection

of

the

E410C,

set

the

band

selector

of

the

marker

generator

to

the

band

which

contains

10.7

MC

and

acljust

the

tunin1

d~al

of

the

marker

generator

until

its

"pip"

also

aJJpears

on

the

response

curve.

Continue

to

rotate

the

marker

generator

dial

until

the

two

"pips"

coincide.

Exact

coincidence

will

be

shown

hy

the

appearance

of

"wiggles"

at

both

ends

of

the

response

curve

caused

by

a

low

frequency

"heat"

hetween

the

two

"fJips"

as

shown

in

Figure

10.

The

reading

on

the

dial

of

the

marker

generator

shoulcl

be

close

to

or

exactly

at

10.7

MC.

Then

set

the

marker

generator

dial

to

10.775

MC

(10.7

MC

+ 75

KC),

resulting

in

a

picture

similar

to

Figure

11.

16

•

I

----

-T '

' -

? •

-

~,ill

-

.-.:.-.,

Fig.

10

Fig. 11 Fig.

12

If

the

10.775

MC

marker

falls

too

low

down

on

the

curve,

or

too

close

to

the

10.7

MC

crystal

"pip",

the

primary

and

secondary

of

the

I.

F.

transformer

should

be

adjusted

to

coincide

with

the

manufacturer's

illustration.

As

a check,

the

marker

gen-

erator

dial

should

be

shifted

to

10.625

MC

(10.7

MC

-75

KC)

and

the

position

of

the

"pip"

noted.

The

10.625

MC

"pip"

should

be

located

symetrically

opposite

to

the

"pip"

at

10.775

MC

as

shown

in

Figure

12

unless

otherwise

inclicated

in

the

manu-

facturer's

instructions.

IMPORTANT

NOTE:

Although

adjustment

of

the

I.F.

transformer

for

the

response

shape

and

bandwidth

as

indicated

by

the

manufacturer

is

desired.

sensitivity

or

gain

of

the

I.

F.

stage

should

not

be

sacrificed

for

unusually

broad

bandwidth.

When

adjust-

ing

I.

F.

transformer

for

150

KC

bandwidth.

as

in

this

discussion,

the

adjustment

should

result

in

"tallest"

(highest

gain)

fJattPrn

with

the

widest

band

width

possible.

In

most

cases

it

would

be

better

to

sacrifice

sorne

hand

width

for

more

gain.

With

the

particular

I.

F.

stagP

comph=•tely

aligned,

thP

red

alligator

clip

of

the

output

cable

of

the

E41

OC

is

moved

to

the

grid

of

thP

I.

F.

stage

closer

to

the

front

end

of

the

receiver,

and

the

black

alligator

clip

of

the

same

cable

to

a

ground

point

near

the

grid.

Since

there

will

he

an

additional

stage

of

am1>lification

it

will

be

necessary

to

attenuate

(reduce

in

amfJlitude)

the

output

of thP

E410C.

Rotate

the

coarse

outrJut

switch

one

position

counter-clockwise

and

readjust

the

fine

output

control.

Do

not

touch

the

pattern-aniplitude

control.

The

vertical

amplitude

of

the

scope

trace

should

be

the

same

as

in

the

This

stage

should

now

he

aligned

as

in

the

using

thP

manufacturer's

instructions.

In

a

similar

manner

align

the

stages

up

to

tl1e

converter

stage.

NOTE:

As

the

output

cable

of

the

E410C

is

moved

to

the

grids

of

the

preceding

stages,

the

receiver-responsP

cable

remains

connected

to

the

limiter

grid

leak

resistor.

The

final

I.

F.

adjustment

is

usually

madf'

with

the

outfJUt

cable

of

the

E410C

connected

to

the

mixer

grid

of

the

converter

tube.

It

is

advisable

to

slightl.Y

readjust

the

I.

F.

transformPrs

previously

adjusted

to

obtain

an

over-all

I.

F.

response

curve

which

most

closely

apfJroximates

the

manufacturer's

recommended

shape

and

hand

width,

and

whose

vertical

amplitude

on

the

screen

of

the

oscilloscope is

the

maximuni

obtainable.

B.

DISCRIMINATOR

ALIGNMENT.

When

a

frPquency

modulated

signal

from

an

F.M.-I.F.

system

is

applied

to

a dis-

criminator,

a

voltage

will

be

developed

across

the

discriminator

load

resistors.

As

the

frequency

of

the

F

.M.

signal

shifts

from

the

average

carrier

frf'quency

at

any

one

instant.

to

a

higher

frequency,

an

output

voltage

develops

across

the

discriminator

load

resistors,

with

a

particular

polarity

in

respect

to

ground.

At

another

instant

the

fre-

quency

of

the

signal

being

transmitted

will

be

the

average

carrier

frequency.

At

that

instant.

the

voltage

across

the

discriminator

will

be

zero.

At

another

instant,

the

F.M.

signal

is

at

a

lower

frequency

than

the

average

carrier

frequency

by

the

same

amount

that

it

was

above.

At

that

moment

the

voltage

across

the

load

resistors

will

be

exactly

equal

to

that

in

the

first

instant,

but

of

opposite

polarity.

17

Therefore

the

application

of

an

F

.M.

signal

to

a

discriminator

produces

an

alter-

nating

voltage

across

the

discriminator

load

resistor, whose

frequency

is

determined

by

the

rate

of

frequency

change

of

the

F.M,

signal

and

whose

amplitude

is

determined

by

the

degree

of

/requenc3.r

shift

of

the

F.M.

signal.

This

results

in

the

well-known "S'"

curve

when

the

F.M.

8ignal

applied

tc1

the

discriminator

is tJroduced

by

a swePp

generator

such

as

the

E410C

and

is

shown

in

Figure

13.

Fig.

13

Since

we

assume

that

the

I.F.

stages

of

the

receiver

under

discussion

have

been

aligned

1>roperly,

the

output

clips of

the

E410C

can

be

connected

to

the

grid

of

either

the

first

or

se-cond I.F.

amplifier

and

ground.

The

alligator

clips of

the

receiver-response

cable

should

be

connected

tc>

point

X

and

ground

as

shown

in

Figure

14.

E410C

R.F.

OUTPUT

CABLE

BL.AC+<

ALLIGATOR

CLIP

LIMITER

r

I

L_DISCRli.lNATOR

Fig.

14

lOAD

RESISTORS

-,

I

RED

ALLLGATOR

.------t--t-""":"'W'I--

C.LI

P

I

:(

------_J

BLACK

llLLIGAl'O

CLIP

E410C

RECEIVER

-RESPONSE

CABLE

As soon

as

the

"S"

curve

appears

on

the

oscilloscope,

the

10.7

Marker

signal

should

be

applied.

If

the

discriminator

transformer

is

properly

aligned

the

..pip"' will

appear

as

shown

in

Figure

15.

Fig. 15

The

advantage

of

the

marker

adder

feature

of

the

E410C is

now

evident.

Because

the

volt.age

at

the

mid

point

of

the

''S"

curve

is

zero,

the

conventional

method

of

marker

injection

into

t}1e

receiver

would

result

in

no

"pips"

appearing

at

the

mid

point.

How-

ever,

in

the

E410C,

the

marker

"pip"

is

injected

in

the

marker

adder.

and

can

be

seen

clearly

at

any

point

on

the

"S"

curve.

18

'

t

If

the

crystal

mark(•r

"1>iJJ''

does

not

come

out

at

the

center

of

the

straight

line

portion

of

the

"S'.

curvr-,

adjust

the

secondary

of

the

discriminator

to

bring

the

marker

''pip"

to

the

center

of

the

straight

line

1>ortlon.

The

primary

of .the

discriminator

is

adjusted

to

make

the

straight

line

portion

of

the

"S''

curve

as

large

as

possible.

1.

Adjust

the

variahle

marker

generator

for a 10.775

MC

(10.7

MC

+ 75

KC)

unmodu-

lated

R.F.

signal. A

marker

"pip'~

should

ap1>ear

at

the

tor>

end

of

the

straight

line

portion

of

the

curve.

2.

Set

the-

variable

marker

generator

for

a 10.625

MC

signal (10.7

MC

-75

KC).

The

marker

should

fall

at

thP

lc>wer

end

of

the

straight

1ine

portion

of

the

curve.

Slight

adjustments

of

the

discriminator

transfc>rmer

trimmer

should

he

made

so

that

the

variable

marker

"pips"

fall

on

the

curve

as

indicated

in

Figure

16

and

the

10.7

crystal

''pip''

is

at

the

center

of

the

straight

line

fJortion

at

the

reference

line.

\,:.Jlt/

i

to

775,MC

b

107

ir.lC

CRYSTAL

Fig.

16

Adjustment

of

the

pri,n

ary

of

the

discriminator

transformer

will affect

thP

overall

amplitude

of

the

discriminator

curVP

and

should

be

adjusted

for

maximum

amplitude

on

the

oscilloscope screen.

It

is

essential

that

the

discrimi11ator respo11se is

adjusted

for

linear

symmetrical

response

since

faithful

reproduction

of

the

F.M.

signal

depends

on

the

response

of

the

discriminator

output.

C.

OSCILLATOR

ADJUSTMENT.

The

adjustment

of

the

oscillator

in

an

F.M.

receiver

is

similar

to

the

adjustment

of

the

oscillator

stage

in

an

A.M.

receiver.

The

basic

procedure

is

as

follows:

With

the

tuning

dial

of

the

F.M.

receiver

set

to

104

M.C.,

the

output

of

the

E410C

is

connected

to

the

antenna

terminals

of

the

receiver

through

a

matching

network

illustrated

in

Figure

17.

RED

CLIP

130

OHM

RESISTOR

8 WIRE

"a.;:;..-.-:

Fig.

17

I •

130

OHM

RESISTOR

Connect

one

end

of

a 130

ohm

resistor

to

each

of

the

F.M.

antenna

terminals

of

the

receiver.

Attach

the

red

alligator

clip

of

the

E410C

output

cable

to

the

free

end

of

one

resistor

and

the

black

alligator

clit> to

the

free

end

of

the

other

resistor.

Since

the

termination

of

the

output

cable

is 50

ohms

and

the

impedance

of

the

antenna

input

of

the

receiver is 300

ohms

an

imJ>Pdence

mismatch

would

occur

if

the

19

E410C

cable

were

connected

dire(·tlv

to

the

antPnna

tClrminals.

The

addition

of

the

•

130

ohm

resistors

ut

each

end

of thP 47

(>l1m

rt->~istor

brings

the

imJJPdance

<1f

thP

E410C

as

Sf"en

by

the

antenna

to

47 + 130 • 130 ()hms

<)r

307 ohm~. a valu<· mur-h cl(,ser

to

the

impedance

of

the

antl•nna.

ThE:'

im1Jed.ance ''lof1king''

out

of

the

E410C

out11ut

cable

is sufficiently

high

sc>

as

to

not

disturb

th<"

(,ut11ut

cable>

termination.

The

"Band

Select<lr''

switch

of

the

E410C

is rc)tated

to

band

E;

and

the

main

tuning

dial

is

set

to

approximatr•ly

104 M.C.

The

swe(•Jl \vidth

control

is

advanced

until

a

60 cycle low

frequency

note

is

heard

in

the

SJ)eaker of

th<'

F.M.

rec£'ivcir. if

the

receivPr

oscillator

is

adjusted

properly.

If

no

sot1

n<l

is

heard,

the

rPceiver

oscillator

will

need

readjustment.

Tracking

of

the

entire

dial

should

be

JJerformPd

by

the

eonventi()nal

A.M.

method

as

described

in

the

receiver

manufacturer's

service

manual.

Another

method

frequently

used

is

the

use

of

the

variable

marker

generator

(such

as

the

Precision

Apparatus

E200C)

and

a

VTVM.

The

output

of

the

E200C

is con-

nected

to

the

antenna

terminals

of

the

rPceiver dirPctly

and

set

up

for 104 M.C.

unmodulated

R.F.

The

VTVM

is

connected

across

the-

grid

leak

resistor

of

the

limiter

stage.

If

the

oscillator

of

the

receiver

is

adjusted

properly

a

maximum

reading

on

the

VTVM

will

be

obtained

when

the

tuning

dial

of

the

receiver

is

set

to

the

same

frequency

(104

M.C.)

as

the

E200C.

As

in

the

preceding

procedure,

tracking

of

the

entire

dial

will

be

done

using

the

conventional

A.M.

method.

Other

similar

methods

include

the

use of

an

unmodulated

R.F.

signal

and

a

VTVM

connected

across

the

discriminator

load

resistors.

In

this

case

the

reading

of

the

VTVM

will

be

zero

if

the

oscillator

is

adjusted

pro11er1y

with

the

recf'iver

dial

set

to

104

M.C.

The

VTVM

will

read

minus

at

a

dial

sPtting

of thf'

variable

generator

just

below 104

M.C.

and

the

reading

will be -!-

at

a

dial

setting

just

above

104 M.C.

on

thf'

variable

marker

generator

dial.

Another

method

of

checking

is

to

use a frequent·y

modulated

signal

frt>m

the

E410C

and

the

same

set

up

as

in

checking

the

I.F.

or

discriminator

stage

with

an

oscillosco1Jc

as

the

indicating

device.

With

the

E410C

~et for a 104 M.C.

swept

signal

and

thl'

clut11ut

cable

c>f

tbe

E410C

connected

throug-h

the

130

ohm

resistors

to

the

antenna

t0rminals

of

the

r(~ceiver.

the

receiver

is

tuned

to

104 M.C. A

t_v11ical

res1>onse 11attern,

such

as

that

for

an

alignPd

I.F.

or

discriminator

should

appear

on

the

oscilloscoJJe de11ending

on

whprp

thf>'

rf'-

ceiver

response

cable

alligator

cliJJs

ar{~

c<1nnected (

grid

lrak

resistor

f<Jr

th£'

I.F.

response

curve

and

the>

<liscriminator out11ut

resistors

for thP rlis<'riminat<lr

''S"

curve).

D. OVERALI.1

CHECK

()I? R.F.

AND

I.1"~.

STAGES.

As

a

double

ehPC'k

of

tht•

c11mbinpr)

<)J>e-rati<ln

c)f

thP

R.F.

and

I.F.

stages,

the

above

test

can

be

usc1cl.

With

t

hci

sPt u

1>

as

dt•serihPrl

ahc>\rp,

the

dial

of

the

E4

1

OC

should

he

set

to

selected

frcquencil-'s

at

tht->

l<>w,

midclle ancl

hiri-h

(->nd

of th~

F.M.

bancl.

and

thl•

dial

of

the

F.M.

r<)c•eivPr

~Pt

t<)

tbE:'

same

fret1uency

as

the

E410C

clial.

The

rPsultant

wave

shape

on

the

c}scill<)SCl)l>t

1

ma.v·

l1e

f'xaminerl

ll'-1'

comJJarison

with

the

curves

recom~

mended

in

the

manuf

acture-r':;

instructions.

Slight

final touchu11

of

thr

I.F.

transformrrs

can

be

made

for

maximum

c)UtJJut

C()nsistant

with

the

11r()per

band

width.

The

use

of

the

Marker

Generator

in

this

a1>11lication

i~

rec<)mmPnrled. (Tsing

thr

same

11rocCldurt"l,

with

the

receiver

cable

connected

t11

th0

<li~;criminator

load

resistor:;;,

tht:.

discriminatc)r

wave

shape

may

be

double-rh0cke<1

on

an

ovPrall OJJerational basis.

2.

TELEVISION

RECEIVERS

There

are

two

basic

t:yp<•s

of tPlevisi11n

r<'-Ceivers.

The

oldPr

units

generally

used

an

I.F.

in

the

20 M.C. region

and

employed

tw<)

srJlarate

I.F.

channels.

one

for

sound

an<l

the

other

for

video

(picture).

20

A

I

'l'he

more

modern

sets

011rrate

with

I.F.

stages

in

the

40 M.C.

rClgion

and

use

only

one

I.F.

channrl

for amJ)lifying

hc>th

tht:.

video

and

audio

I.F.

signal

(intercarrier

s>-

1

stem).

In

tbP older, se11arate

channel

syst{'m,

trat)s

were

included

to

completPly se-1Jarate

thP two

channels,

in

order

to

JJrevent

int0rf

PrPnce

caused

by

souncl

signals

getting

into

the

video

channel.

For

this

rPason the-

twc1

C'hannpl

type

of

receiver

is

more

compli-

cated

and

required

a mor(l t•laboratt-'

alignment

11rocCldure.

SEPARATE

SOlJND

AND

PICTlTRE

I.F.

CHANNEL.

The

six

basic

steps

in

the

alignment

of

separate

channel

receiverR:

are

a!-i

follows:

A.

Video

(picture)

I.F.

traps.

B. Pict11re

I.F.

transformers.

C. Soun<l di£icriminator.

D.

Sound

I.F.

transformers.

E.

R.F.

adjustment.

F.

R.F.

oscillator

adjustment.

The

alignment

description

which

follows is

necessarily

very

general

in

character,

and

should

not

he

f<)llow<~cl

explicitly

in

the

alignment

of

any

on{'

particular

model

of

T.V.

receiver.

ALWAYS

FOLI.,OW

THE

MANlTFACTURER'S

DETAILED

ALIGNMENT

AND

TEST

PRO(~EDlJRES

WHEN

SERVICING

A

TELEVISION

RECEIVER.

A.

ALIGNMENT

OJi'

PICTllRE

(VIDEO)

I.F.

TRAPS.

A

picture

I.F.

trap

is

basically

a tunecl

circuit

adjuste(I

to

rClsonance

at

a

particular

frP.quency.

Most

manufa<~tur<•rs

v.

1ill eall for

alignmf'nt

of

the-sP

traJJ8

using

a fixed

unmodulated

R.F.

signal

aH

an

injection

sourc(

..

,

and

a

VTVM

(vaeuum-tuhe

vc>1tmeter)

a.s

an

indicating

,lt~vice.

In

such

an

alignment.

thP

I.F.

tra1>

is acljustecl for

minimum

indication

on

the

VTVM.

If

tbP

E410C

usPr

has

availal>le

an

accurate

~ignal

gP11('rat<Jr

such

as

the

Precision

AJJJJaratus l\,fod{'l

E200C.

he

ma.v

use

the

gt•nerator

as

the

Hignal

source.

If,

on

thr

<>ther

hand,

tbP

accuracy

(>f

the

mark

Pr

genPratc1r availal1le is questionable,.

the

E410C provi(les two clistinct

mfltb<>fls

c}f

using

the

crystal

oscillator

circuit

of

the

generator

to

obtain

crvstal

mark(lt

accuracv.

-.

A

VTVM

is

then

cc>nnPCt(1d

across

the

vide-,1

seccJnd cletPctor Ioarl resistor.

With

the

unmodulated

R.F.

signal

of

J)ro1,er frt•quency aJltJliecl

to

the

trap

under

alignment,

the

trap

trimmer

or

slug

should

bP

tunecl for a

minimum

indication

on

the

VTVM.

21

E:.

410,'

CRYSTAL

---t--rT

OF

TRAP

FREQUENCY

......

0

CG

0

~.

'

...

$'"~

:

--...

I

..

-~

..

-

1~•

=

l.

0

,

,_

..

'

0

•

i

1-'-.

~.:..a

• •

:0

......

'

0

o-

...

-;5·

..

~·

' 0

..•..

0

t.'

••

'

·~

~

.....

I

0

T v RECEIVER

UNDER

TE.ST

Fig.

18

VIDEO

DETECTOR

LOAD

R[SISTOR

VTVM

PRECISION

CZ]

.

The

same

procedure

is

used

on

all

the

picture

I.F.

traps

listed

in

the

manufacturer's

instructions,

inserting,

each

timet

the

proper

crystal

for

each

type

frequency

specified

in

the

directions.

The

conventional

sweep

generator

which

does

not

have

the

marker

adder

feature

of

thP

E41

OC

cannot

he

used

readily

for

observation

of

the

marker

"pip"

in

the

trap

in

visual

tra1>

adjustment.

This

is

because

at

the

trap

point

the

output

voltage

is

zero

or

vflry close

t<>

ze·rc)

and

a

markPr

of

the

trap

frequency

at

the

I.F.

stage

will

also

he

of

zflr<>

V<>ltage

and

will

not

ar>J)Par

on

the

response

curve.

However,

using

the

E410C

and

a

rrystal

t)f

tht• ]>roper

tra1>

frequency,

the

trap

can

be

adjusted

visually,

since

the

marker

will

a1>1>ear

at

thP

t>r<)pPr

frequency

along

the

response

curve,

and

the

trap

trimmer

can

be

adjusted

to

move

the

trap

to

the

marker.

This

feature

of

the

E410C

makes

alignment

of

traps

much

easier.

Another

method,

similar

to

the

above, is

the

use

of

an

accurate1y

calibrated

marker

generator

such

as

Precision

Apparatus

E200C.

As

the

dial

of

the

marlcer

generator

is

moved

across

the

frequency

hand

of

the

I.F.

stage)

the

marker

''pip''

will movP

alon.{{

the

response

curve

as

seen

on

the

scope

and

at

zero

voltage

points

(trap

points)

will

indicate

the

position

of

the

trap.

In

this

a11plication

the

marker

generator

(Precision

Apparatus

E200C)

output

i~

C(lnnected thrc>ugh

the

marker

input

cab1e to

the

marker

input

connector

of

the

E410C.

The

E410C

is

set

to

the

center

frequency

of

the

I.F.

band,

and

the

E200C

is

set

to

the

band

which

will

produce

the

frequencies

around

the

setting

of

the

E410C.

The

tra11

points

can

then

be

read

off

on

the

dial

of

the

marker

generator

(Precision

A11paratus

E200C

or

equivalent)

and

any

necessary

corrections

made

by

adjustment

of

the

tra1>

trimmer.

Thf'

T.V.

station

signal

will

also

mark

the

sound

trap

quite

accurately

as

explained

on

page

33.

TRAP

2:2.~HC 1 A

h-r-n-1'-

Fig. 19

B.

VIDEO

I.F.

TRANSFOR.MERS.

In

order

to

obtain

the

wide

band

width

required

in

a

T.V.

picture

(video)

I,F.

system.

it

is

customary

to

use

"staggeredu

I.F.

tuning

(i.e.:

each

picture

I.F.

is

tunen

22

•

l

to

a

slightly

different

frequency)

or

in

other

cases

resistance

loaded,

(

the

uQ"

of

the

circuit

is

reduced

and

the

bandwidth

is

increased

at

the

expense

of

gain.

More

stages

are

generally

requirecl

with

resistance

loading).

In

general,

the

manufacturer's

instructions

will

usually

indicate

the

individual

align•

mPnt

frequPncy

of

each

video

I.F.

stage.

After

each

individual

stage

has

been

adjusted

to

its

particular

frequency,

the

overall

picture

for

the

total

I.F.

system

will

resemble

Figure

19.

Occasionally.

instead

of

visual

alignment

of

the

video

I.F.

stages.

the

manufacturer

may

recommend

simple

peaking

adjustment

using

an

unmodulated

R.F.

signal

from

a

marker

generator

and

a

VTVM.

If

this

method

is

used,

there

should

be

a final

check•

ing

of

the

overall

response.

using

the

E410C

with

the

output

of

the

E410C

coupled

to

the

converter

tube

by

means

of

several

turns

of

wire

wrapped

around

the

converter

tubet

and

connecting

the

receiver

response

cable

of

the

E4I0C

across

the

video

second

detector

load

resistor.

Using

this

procedure

slight

individual

adjustments

of

t.he

I.F.

transformers

should

be

made

to

obtain

the

proper

overall video

I.F.

response

curve.

NOTE:

The

figure

representing

a

typical

video

I

.F.

response

curve,

will

not

necessarily

be

the

pattern

which

will be

obtained

in

all

picture

I.F.

systems.

Some

of

the

simpler,

less

expensive

receivers,

do

not

incorporate

"fl.at

top"

picture

I.F.

response

curves

and

may

not

produce

the

obvious

trap

dips

at

either

end

of

the

response

curve

as

seen

on

the

figure.

It

is

therefore

of

utmost

importance

that

the

type

and

shape

of

the

overall

r

~ponse

curve

for

the

particular

receiver

being

adjusted

should

be

obtained

from

the

manufacturer's

service

instructions

for

the

model

being

serviced.

A

typical

overall

video

I.F.

response

curve

check

is

given

as

follows:

TO

IF

VtDEO

DETECTOR

STAGES,.__

_..,.

___

__,

-

TO

VIDEO

.__...,._

__

---1

....-_.,._..

AMPLI F

tER

RED

CLIP

BLACK

CLIP

Fig. 20

E-4I0

t.

RECEIVER

RESPONSE

~~O:::::::::~

CABLE

I

---TO

.__

_

_,

RECEIVER

R[9PONSE

CONNECTOR

OF'

E-410<..

1.

Connect

the

E410C

receiver

response

cable

alligator

clips

to

the

top

(use

red

clip)

and

the

ground

point

(use

black

clip)

of

the

video

second

detector

load

resistor.

2.

Make

a

loop

of

several

turns

of

wire

and

slip

it

over

the

T.V.

set

converter

tube.

Connect

the

red

alligator

clip

on

the

E410C

output

cable

to

the

end

of

the

loop.

Connect

the

black

alligator

cli11

to

a

ground

point

close

to

the

wire

loop.

3.

If

possible,

disable

the

local

oscillator,

unless

the

tuner

uses

a combine-d

mixer-

oscillator

tube.

(Follow

the

manufacturer's

directions

for

the

injection

point

of

the

swflep

generator

output).

4.

1,he

band

selector

switch

and

main

tuning

dial

of

the

E410C

is

set

t<)

th{'

picturP

I.F.

center

frequency

(let

us

assume

it

to

be

25.75

MC).

28

,

•

'

5.

If

the

manufacturer's

instructions

call

for

adjustment

of-

the

·receiver ·

I.F.

bias

to

a specified volt.age,

the

front

panel

control

of

the

T.V.

receiver, which-

adjusts

this

bias

(usually

labeled

"contract"

or

"picture'')

should be

set

to

·the

proper

value

'using a

Precision

Apparatus

vacu11m

tube

voltmeter.

IMPORTANT

NOTE:

Manual

adjustm"ent of

the

I.F.

bias

control

acts

as

an

atten-

uator

control,

reducing

or

increasing

the

strength

of

the

.input

signal

from·

the

E410C;

in

addition

to

the

adjustment

of

the

outpllt

control

and

coarse

attenuator

switch

of

the

E410C.

6.

If

the

set

uses A.G.C.

(automatic

gain

control) over-ride

this

bias

by

a

set

of -test

leads

connected

to

the

"A.V.C. voltage1

.'

jacks

of

the

E200C. Follo,v

the

instructions

in

the

E200C

manual

and

use

a

VTVM

to

measure

the

exact

over-ride voltage.

7.

Refer

to

Figure

5

and

set

up

the

rest

of

the

connections

(for

the

marker

generator

to

the

E410C,

and

the

E410C

to

the

oscilloscope,

as

shown).

8.

Rotate

the

S\Yeep

width

control

of

the

E410C

in

a clocl{\Yise ·direction,

and

adjust

the

coarse

attenuator

switch

and

fine

output

control

until

a

response

trace

appears

on

the

oscilloscope

as

shown

belo,v. ·

If

the

coarse

and

fine

output

switch

and

control

is

set

too

high

there-will

be

distor-

tion

of

the

pattern

due

to

overloading of

the

I.F.

stages.

This

will

appear

as

seen

in

Figure

21.

The

obvious

remedy

is

to

reduce

the

output

to

below

the

overload

point,

•

E410C OFF CENTER

FREQ.

• Fig.

21

'

B

CORRECT E410C

SWEEP FREQ,

Fig.

22

C B

E410C OFF CENTER

FREQ.

Fig.

23

li

the

sweep

width

control

is

set

too

far

in

the

counter-clockwise position, insuffi-

cient

sweep will occur. A

small

section

of

the

overall

response.

will

_appear

on

.the

··oscilloscope screen.

For

example,

the

circled

portion

of

the

overall

response

in

Figure

19

(from

A

to

B),

in

the

expanded

form,

,yould

appear

if

the

sweep

width

were

too

low

The

solution

would

be

to

rotate

the

control

clock\Yise to

increase

the

sweep

width.

If

the

center

frequency

of

the

sweep

generator

was

not

at

the

center

frequency

of

the

I.F.

response

curve

would

appear

on

the

response

curve

as

in

Figure

21

or

23.

The

entire

right

hand

section of

the

respon~e

curve

from

A

to

B

would

be

missing,

and

a

section to

the

left

of

the

left

trap

would

appear

on

the

trace.

By

rotating

the

E410C

main

dial

slightly

the

entire

I.F.

trace

can

be

brought

to

the

center

of

th€!

oscilloscope.

screen. ·

NOTE:

(The

samA

procedure

should

be

used

in

F.M.

receiver

alignment

for

ohtaining

an

F.M.,

I.F.

trace

that

is

free

from

distortion

due

to

overloading,

not

centered

due

to

m.isadjustment

of

the

E410C dial,

or

showing

only

a

portion

of

the

trace

due

to

insufficient s,Yeep).

On

the

other

hand,

there

are

times

when

it

may

be

necessary

to

have

only

a

section

of

the

response

curve

on

the

oscilloscope.

The

user

may

desire

to

examine

more

closely

a

small

portion

of

the

overall response.

In

this

case,

reduction

of

the

s,veep

width

,yill

expand

the

portion

of

the

response

curve

to

be

examined,

and

a

slight

rotation

of

the

main

tuning

dial

will

bring

the

expanded

section

of

the

response

curve

to

the

center

of

the

oscilloscope screen.

NOTE:

Never

center tlie response trace

by

using

the

horizontal centering control

of

the

oscilloscope.

Always

center

the

trace

by

slight

rotation

of

the

main

tuning

dial

of

the

E410C.

24

•

.I

•

'

•

'

)

C.

MULTIPLE

MARKING.

.The

introduction

of

"pips"

oi:

marlcers is

now·

necessary

to

determine

whether

the

center

frequency

of

the

I.F.

is

correct,

and

to

measure

the

bandwidth

and

indicate

the

position

of

the

picture

and

sound

frequencies

on

the

response

curve.

Again,

as

is

the

case

in

the

F.M.

receiver,

an

external

marker

generator

(such

as

Precision

Apparatus

Model

E200C)

may

be used.

The

internal

crystal

oscillator

can

be

used

to

modulate

the

marker

generator

thus

producing

multiple

markers

of

crystal

accuracy.

For

example,

with

the

E200C

set

to

23 megacycles, a

two

megacycle

crystal

connected

to

the

crystal

socket of

the

E410C

\vill

produce

marlcers

at

23

MC,

21

MC,

25

MC,

27

MC,

etc.

T11e

amplitude

of

the

marker

upips"

can

be

controlled

by

rotation

of

the

ma::lcer

size

control

and

the

,yidth

of

the

"pips"

by

operation

of

the

marker

width

control.

There

may

be

"pips"

which

are

harmonics

of

the

2

MC

crystal

itself

at

221 24, 26, 28

MC,

etc.

These

Can

be

identified

by

the

fact

that

they

will

remain

stationary

if

the

frequency

dial

of

the

E20QC

is

roclced

(rotated

slightly

to

the

right

nnd

left

of 23

megacycles).

The

"pips"

that

move

with

the

23

megacycle

"pip"

are

spanned

exactly

2

MC

apart.

The

original

23 megacycle

"pip"

can

be

identified

by

removing

the

crystal

from

its

socket

at

which

time

the

multiple

2

MC

markers

will

disappear.

With

the

4.5

MC

crystal

(supplied

with

the

E410C) t\yo

marker

"pips'!

can

be

superimposed

on

the

video

I.F.

response

curve, one

at

25.25

MC,

marking

the

picture

carrier,

and.

one

at

21.25 M.C., marlcing

the

sound

carrier

position.

This

feature

is

useful

in

the

alignment

of

T.V.

receivers.

In

this

application

the

E200C

dial

would

be

set

to (16.75

MC

(16.75

MC+

4.5

MC=

21.25

MC),

(16.75 + 2X4.5

MC=

25.75

MC)

.

It

should

be

noted

that

a

"pip"

at

22

MC

will also appea!',

,yhich

is

the

fourth

harmonic

of

the

4.5

MC

crystal

itself.

Rotation

of

the

output

controls

of

the

marker

generator

fully

counter-clockwise will

cause

the

disappearance

of

the

21.25

and

25.75

"pips"

and

the

22

MC

"pip"

,vill

remain.

The

operator

should

note

the

position

of

this

"pip"

and

then

bring

back

the

21.75

MC

"pips"

by

increasing

the

output

of

the

marker

generator

(E200C).

The

first

marker

which

is

superimposed

on

the

response

curve

is

the

so-called

mid-

point

marker,

which

in

this

discussion ,vould

be

at

25.75

MC.

This

point

is

shown

in

Figure

24

at

"point A.

It

is obvious froni inspection.

of

tlie figure tluit

the

25.75

1v.IC

marker

is

not

at

tlie ph,ysical center of tlie tesponse cztrue.

•

'

Fig. 24

••

• • •'

•

This

is

the

reference_

frequency

from

which

all

other

frequencies

in

the

response

curve·

are

measured.

The

technician

,yill also observe

that

this

marker-

falls

on

an

almost

vertical

section

of

the

response

curve.

Again

the

marker

adder

feature

of

the

E410C

is

of

great

advantage

in

differentiating

the

position of

the

marker

"pip"

on

the

vertical

section

of

the

curve.

Other

markers

as

recomm.P.nded

by

the

manufacturer

may

be

introduced

as

a check

of

tl1e

over-all

response

curve

shape.

•

NOTE:

The

manufacturer

may

recommend

removal of

the

oscillator

tube

and/or

shunting

(or

bypassing)

of circuits

in

the

R.F.

end

of

the

receiver

to

eliminate

inter-

25

•

'

•

'

,·

I

'

I

•

ference

with

the

video

I.F.

response

curve.

By

rotating

the

channel

selector switch

on

the

front

panel

of_

the

receiver,

any

interference

caused

by

the

R.F.

section of

the

receiver ,yill become

apparent

on

the

I.F.

response

curV'e.

Radical

changes·

in

the

shape

·

of

the

response

curve

indicate

interference.

I.F.

alignment

should

be·

per'formed only

if

the

station

selector switch of

the

receiver is

set

to

a

non-interfering

position.

T.V. receiver

manufacturers

publish response curves

which

almost

always

are

suit-

able

for

local

reception

(strong

signal

conditions).

In

fringe

areas

the

user

should

modify

the

procedure

of

alignment

as

follows:

•

1.

Align

the

receiver ,yith

the

contrast

control

(I.F.

bias)

set

to

¾tl1s of

maximum,

depending

upon

the

expected

input

signal

level.

This

precaution

is

necessary, since

most

receivers will show a

different

response curve

at

high

gain,

due

to

the

so-called

"Miller

Effect".

2.

Insert

the

picture

carrier

marker

(see

manufacturer's

manual

for

proper

frequency),

as usual. ·

3.

Narrow

the

bandwidtl1 of

the

receiver

to

approximately

half

tl1e

bandwidth

recom-

,

..

mended·

for·

strong

signal

reception,

and

place

the

picture

·canier

"pip''··near

·the

top

of

the

curve.

10

NOH·INTERCARRIER

TYPEI

l,F.

SYSTEM

Fig.

25

Io

lHTERCARRIER

TYPE

l.f.

SY8TfJ1II

38

!Ii

40

This

procedure

allo,YS

tl1e

sound

and

picture

to 11

track"

nnder

conditions of low

signal level

and

produces

satisfactory

picture

and

sou:nd 11nder "conditions

wbere

,the

usU.al

type

of

alignment

would

result

in

a

"snowy"

picture

and/or

loss of

sonnd.

It

must

be

strongly

emphasized

that

0

fringe

alignment''

results

in

a

poor

picture

nnder

high

signal

level conditions.

NOTE:

Many

servicemen

have

asked

wliy

the

ideal

response curve

cannot

be achieved

in

practice,

no

matter

how

carefully

instructions

were

followed.

This

is

mainly

due.

to

component

tolerances

in

the

receiver.

The

plate

resistance, amplification factor, etc.,

of tubes varies widely;

the

Q of

tuned

circuits

vary;

resistors

and

capacitors

vary

± 10

to

20

%;

lead

dress varies

from

chassis to chassis. As a

result,

it

is

usually

impos-

sible to

obtain

the

ideal

response

curve.

The

servicemen

should

remember

that

the

CJ'e responds

logarithmically

to

light

intensity

somewhat

like

the

ear

to

sonnd

intensity.

As

in

audio

(sonnd

work) a video

signal

is

judged

to

be

t\vice

as

bright

as

another

if

increased

6

D.B.

Conversely,

the

signal will

be

one-half

as

bright

as

another

if

decreased

6

D.B.

One

D.B.

is

the

smallest

change

in

video signal, detectable

by

the

eye

under

the

most

favorable conditions.

A

variation

in

video

output

voltage of 25%

is

only

2

D.B.

which

will

be

nnnoticed

unless

the

observer is looking

very

carefully

under

ideal

conditions.

26

•

..

'

•

I

"'

I

>

I

i

I

'

I

'

I

•

• •

•

Two

important

points:

a.

It

is

practically

impossible

t?

obtain

an

absolutely

flat

response.

b. ·

The

difference

in

volts of

the

actual

response

curve for

the

idealized

published

response curve

may

be

transformed

into

D.B.

The

resulting

D.B.

changes

will

indicate

the.

effect

on

the

eye of

the

difference bet\veen

the

actual

response curve

and

the

idealized curve

published

by

the

manufacturer.

D. SOUND DISCRIMINATORS

It

is

essential

that

the

sonnd

discrimination

of

a T.V. receiver is

adjusted

accurately,

since

tl1e

proper

alignment

if

the

R.F.

oscillator

depends

on

the

alignmen~

accuracy

of

the

sonnd

discTiminator. A

typical

T.V.

sonnd

discriminator

alignment

follows,

and

is

quite

similar

to

the

alignment

of

an

F.M.

discrimini:ttor· circuit.

1.

The

E410C receiver response cable

alligator

clips

are

connected across

the

load

resistors

of

the

discriminator

output

following tl1e

manufacturer's

instrllctions.

2.

The

E410.C

output

cable is

connected

into

either

tl1e

grid

of

the

limiter

tube

or

the

grid

of

the

I.F.

tube

immP.diately

preceding

the

discriminator

.

3.

The

set

up

of

Figure

5

is

used

for

the

other

connections

in

the

alignment

procedure.

4. ~~The-E410C

is

set

up

to

produce

a

center

frequency

at

the

I.F.

frequency

specified

by

the

manufacturer,

(examples 41.25

MC

or

21.25

MC).

5.

Advance

the

sweep

width

control

until

the

typical

usu

curve

appears

on

the

oscillo-

scope screen.

(Refer

to

page

22

for

procedure

to

follow

if

the

discriminator

is

overloaded,

or

the

sweep··

width

is

insufficient,

or

if

only

a

portion

of

the

response

curve

appears

on

the

oscilloscope

screen).

6. A

typical

signal

of 41.25

MC

or

21.25

MC

marker

is

superimposed

on

the

patt~rn

by

use

of

either

a

crystal

of

the

proper

frequency,

or

a

marker

generator

such

as

the

Precision

Apparatus

.E200C,

and

the

sound

discriminator

transformer

is

adjusted

.if--necessary.

(Refer·

to

the

procedure

for

F.M.

receiver

alignment,

bearing

in

mind·

that

the

marker

frequency

is

21.25

MC

or

41.25

MC).

7.

For

check of

symmetry

and

bandwdith,

refer

to

the

manufacturer's

specifications.

The

bandwidth

of a T.V.

discriminator

is generally

about

50

KC

± 25 KC.

about

the

center

frequency)

..

In

our

example,

the

end

points

(along

the

straight

portion

of

the

"S"

curve) will be 21.275

MC

and

21.225

MC

or

41.275

MC

and

41.225MC.

The

sam""

procedure

as

for

F.M.

receiver

alignment

should

be followed.

E.

SOUND

I.F.

TRANSFORMERS

The

alignment

of

sonnd

I.F.

transformers

is

practically

identical

to

that

of

the

ordinary

F.M.

receiver with.

the

exception

tl1at

the

sound

I.F.

bandwi'dth of

the

T.V.

receiver

is

less

than

that

of

the

F.M.

receiver.

Refer

to

the

manufacturer's

instructions

for

the

response

curve

and

bandwidth.

Follow

the

procedure

for

alignment

of

the

F.M.

receiver

I.F.'s

with

the

necessary changes

due

to

difference

in

frequency

and

bandwidth.

F.

R.F.,

CONVERTER

AND

OSCILLATOR

ADJUSTMENT

There

are

t,,yo

methods

of

R.F.

and

converter

alignment

generally

used

in

T.V.

• •

servicing.

1.

The

R.F.

channel

response

only

is

obtained

on

the

oscilloscope screen.

The

E410C

output

is

injected

into

the

receiver

antenna

and

the

receiver

response

is

taken

at

the

output

of

the

R.F.

tuner

itself.

27

•

I

lj

I

-

2.

An

irldirect

method

is

used

where

the

overall response of

the

R.F.

and

I.F.

stages

is observed

on

the

oscilloscope screen.

The

E410C

output

is

injected

into

the

antenna

terminals

and

the receiver response

output

is

taken

from

the

grid' resistor of

the

•

limiter tube

or

from

the

load

resistor

of

the

discriminator.

This

is

an

indirect

method

since

the

actual

pattern

will

be

primarily

that

of

the

overall

I.F.

response

curve.

The

general

method

or

procedure

in

the

indirect

method

is

to

first checlt

the

overall

I.F.

response

by

injecting

the

E410C

output

at

the

input

of

the

I.F.

stages

(the

converter

tube

coupling

method

as

described

on.page

21).

The

respo!lse

pattern

is

then

observed

and

the

amplitude

and

overall

shape

of

the

curve

is

noted.

The

outPut of

the

E410C

is

then

switched

to

the

input

terminals

of

the

receiver

and

is

attenuated

to give

the

same

size

response

on

the

scope.

Any

misalignment

of

the

R.F.

section ,yill sho,v

up

as

a

change

in

the

wave

shape

of

the

I.F.

response.

If

necessary,

the

adjustments

as

called for

in

the

m~nufacturer's

instruction

bool::::

should

be

followed. Tlie setup using tlie indirect 1netliod is also to

be

used

to

clieck

tlie ouerall R.F.,

l.F.

response

of

the T.V. receiver and slto[fld always be used

as

a final clieck

after

aligning a 1'ecciver.

The

actual

station

carrier

can

be

used

as

picture

and

sound

markers

as

follows:

Tune

in

a T.V. st.ation

on

the

receiver.

If

a source of

high

frequency

marker

signals

is

not

available

the

following

method

can

provide

a sufficiently

satisfactory

wave

shape

check:

a.

With

the

vertical

gain

control

of

the

oscilloscope

set

to

zero,

locate

the

oscilloscope

trace

in

the

exact

center

of

the

screen.

h.

the

front

end

response

curve

in

full view

on

the

oscilloscope screen.

The

setting

of

the

E410C

sweep

,yidth

control

should

be

slowly

reduced

and

the

E410C

tuning

dial

adjusted

until

only

the

portion

of

the

response

curve

as

indicated

in

Figure

26

appears

centrally

located

on

the

scope.

0 FRONT ENO RESPONSE

CURVE

PICTURE

CARRIER

.

'-

SOUND

CARRIER

•

~

SOUND

CARRIER HUMP EXPANOEO

BY

\::,;;

REDUCTION

OF

SWEEP

WIDTH

CONTROL

ANO

ROTATION

OF

E4l0

DIAL

TO

MOVE

EXPANDED CTION

TO

CENTER

OF

SCOPE.

I

0

Fig. 26

CENTER

OF

:__

__

EXPANDED TRACE

THE

E-410 DIAL SETTING

INDICATES APPROXIMATE

FREQUENCY

OF

CENTER

SECTION

OF

SCOPE

TRACE

(POINT

"X")

c.

The

E410C

tuning

dial

reading

at

this

setting

indicates

the

frequency

of

the

middle

part

of

this

section of

the

response curve.

The

same

procedure

can

be

used

to

check

the

R.F.

sound

carrier

and

picture

c~rrier

"humps"

of

the

response

curves.

28

•

,.

•

Some

manufacturers

may

recommend

the

use of a

·heterodyne

frequency

meter.-

HoWever·the above

methods

are

quite

adequate

and

are

as

satisfactory

as

the

frequency

meter

metl1od or

other

similar

procedures

.

•

VII. INTERCARRIER APPLICATIONS

As

pointed

out

previously

more

modern

receivers

employ

a single

channel

for

the

amplification of

both

audio

and

video

I.F.

sign::ils

in

the

I.F.

stages

(intercarrier

type).

The

alignment

of

the

receiver is

usually

simpler

than

separate

sound

and

picture

I.F.

channel

type,

since

there

is

only

one

channel

to

be aligned.

In

addition,

the

use

of

traps

is

not

necessary,

and

trap

alignment

is eliminated.

The

basic

steps

in

the

alignment

of

intercarrier

type

receivers is

as

follows:

1. Over-ride of

AGC

bias.

2.

Alignment

of

I.F.

transformers.

3.

Alignment

of

sound

circuits.

4.

R.F.

and

converter

alignment.

.

5.

R.F.

oscillator

alignment

.

NOTE:

It

must

be

emphasized

that

great

variations

are

encountered

in

circuit

<let.ails.

Some

receivers use

ratio

detectors,

some

gated

beam

detectors

and

othei:s locked-oscillator

detectors,

as

,yell

as

the

older

limiter-discriminator

type

of

detector

for

sound

detection.

These

instructions

must

therefore

be

very

general

and

we

again

must

stress

the

importance

of

using

the

manufacturer's

instructions

for

specific

details

as

to

points

of

injection

of sweep

signal

and

tal.;e-off

of

receiver response

output,

as

,vell

as

point

of

adjustment

of

trimmers

and

the

shape

of waveforms

to

expect.

1.

OVER-RIDE

OF A.G.C.

BIAS

As sho,yn

in

Figure

5,

an

adjustable

over-ride

bias

can

be

most

conveniently

obtained

from

the

E200C.

See

the

instruction

book

for

the

E200C

on

the

use of

the

A.G.C. voltage

function

of

tl1e

E200C.

The

bias

scale divisions of

the

E200C

serve

as

a guide,

but

for

optim11m

results

use

a

Precision

Apparatus

V.T.V.M.

and

adjust

to

the

exact

value

recommended

by

the

receiver

manufacturer.

2.

ALIGNMENT

OF

I.F.

TRANSFORMERS

Since

traps

are

not

used

in

conventional

intercarrier

receivers,

alignment

is

rela-

tively

simple.

There

are

hYo

basic

marl::::er

points

on

the

curve.

a.

The

sound-carrier

marker

is

placed

10%

up

the

curve.

b.

The

picture-carrier

marlter

is

placed

50%

up

the

curve.

NOTE:

Since

!::OD)e

intercarrier

receivers

are

designed for local oscillator

operation

on

the liigli side ,vith

respect

to

channels

2-6,

but

on

the

loiv side

,yith

respect

to

channels

7-13,

in

this

type

of receiver,

the

response curve

must

be completely

sym-

metrical

since

the

sound

and

picture

I.F:

carriers

,vill reverse positions

during

use of

the

receiver.

After

the

sonnd

and

picture

marlters

have

been

placed

at

the

proper

position

on

•

the

·curve,

by

use

of

the

multiple

marker

method,

using

the

4.5

MC

crystal,

as

dis-

cussed

on

page

25,

the

band-pass

of

the

I.F.

should

be

checl::::ed.

In

T.V.

worl::::,

the

band-pass

is

defined

as

the

nnmher

of megacycles

behveen

the

half

voltage ·points gn

29

•

I

,,

'

I

"

I

fI

,,

'

f

•

'

I

•

'

the

reSponse curve,

unlike

that

of

the

F.M.

or

A.M.

receiver,

where

the

band-pass

is

defined

as

the

width

of

the

flat

portion

at

the

maximum

voltage of

the

response curve.

The

E200C is

ideal

for

marking

intercarrier

response curves,

as

well

as

peaking

indi-

vidual

stages

as

recommended

by

some

manufacturers.

Other

manufacturers

\Yill

recom-

mend

the

peaking

of

individual

stages

using

the

marker

generator

only,

and

then

to

make

&al

adjushnents

using

the

sweep

generator

for over-all response

and

the

marker

generator

for

sound

and

picture

markers.

Pealcing

can

be

done

most

effectively as

follows:

(1)

Set

the

E200C

at

the

peaking

frequellcy specified

by

the

manufacturer

for -the

particular

stage. · ·

(2)

Set

the

E410C

to

indicate

the

complete response curve of

the

I.F.

system.

(3)

Adjust

the

slug

or

trimmer

of

the

coil to

be

peaked,

observing

the

position

of

the

niarker

on

the

screen

of

the

oscilloscope.

Note

tlzat tlie sh.ape

of

tlie curve clianges

during tlzis procedure

but

is to be co11ipletel31 disregarded.

Tlie

stage is pealzed

wlien tlze 11iarker ~'pip'' is

at

tlie liiglzest

point

on

tlze oscilloscope screen,

regardless

of

the

shape

of

the

response

curve.

Subsequent

st.ages

are

to

be pea/zed

in

the

same

11:ianner.

3.

ALIGNMENT

OF

SOUND

CIRCUITS

.

Because

sound

circuits

vary

greatly,

only

the

basic

principles

can

be

discussed

in

these

instructions.

The

sound

signal

in

an

intercarrier

receiver is

obtained

by

picking

out

the

4.5

MC

beat

between

the

sound

and

picture

carriers

of

the

T.V.

station.

This

beat

frequently

is

accepted

by

a 4.5

MC

"trap"

or

by

a

tuned

frequency

transformer.

Because

this

4.5

MC

frequency

is

determined

by

the

spacing

of

the

station

carriers,

it

is

not

affected

by

tl1e

setting

of

the

fine

tuning

control,

and

it

is

therefore

essential

to

tune

the

sound

circuits

to

e.i:actlly 4.5

MC

using

the

4.5

MC

crystal

supplied

,vith

the

E410C.

Careful

adjushnent

of

the

F.M.

detector

is

necessary

to

eliminate

or

minimize

"buzz"

from

the

sound

signal.

Sound

Slzelf.

The

better

designed

intercarrier

receivers

provide

adjustment

for

obtaining

a

sound

shelf•

on

the

response

curve

as

shown

in

""Figure 27.

The

sound• ·carrier

marker

should

be

placed

half

\Yay

along

the

shelf

as shown.

This

shape

of

response

curve

minimizes

amplitude

modulation

of

F.M.

sound

carrier

as

it

swings·

through

its

center

frequency,

and

provides

better

sound

quality.

PIClURE _

CARRIER

10"/~

Fig.

27

SOUNO

CARRIER

Note

the

symmetry

of

the

curve

(the

receiver

in

question

is

the

type

in

which

the

oscillator

is

on

the

low

side

on

channels

7-13).

The

b8.ndwidth is defined

at

the

50%

point

on

the

response

curve.

In

order

to

obtain

a

general

idea

of

how

the

shape

of

the

response

curve

affects

the

amount

of

A.M.

in

the

4.5

MC

sound

signal,

the

following

facts

should

be

noted:

a.

The

4.5

MC

sound

signal

is

always

amplitude

modulated

to

some

extent

("buzz"

modulation)

by

the

picture

carrier,

and

this

buzz

must

be

e]iminnted

by

proper

dis-

criminator,

or

ratio

detector

alignment,

Plus

proper

design of ·the,limiter-

when

used.

80

-

'

..

•

b.

If

the

sound

carrier

marker

is

placed

too

high

upon

the

response

ci.J.rve,

the

sound

signal·can

be

amplitude

modulated

up

to

100%!!

This

condition

imposes impossible

.

demands

on

the

F:Pi1.

detector

system.

c.

If

the

sound

carrier

level

is

10%

of

maximum,

the

sound

signal

is

amplitude

modu-

lated·

approximately

5%.

The

sound

carrier

should

therefore

be

kept

at

the

10%.

point

on

the

response

curve

to

avoid

"buzz".

This

permits

the

F.M.

detector

to

operate

properly.

•

Alignnzent vs.

"Buzz".

The

picture

signal

itself

sounds

lilce a

rough

60 cycle

"buzz"

This

can

be

easily checlced

by

connecting

a

pair

of

earphones

into

the

video runplifier

of

the

T.V.

receiver.

The

conventional

discriminator

accepts

F.M.

signals

and

rejects

A.M.

signals

at

the

center

point

of

the

"S"

curve

when

properly

aligned.

To

further

reject

A.M.

signals

("buzz")

at

other

points

on

the

"S"

curve, a 4.5 limiter~amplifier

is

generally

used

to

clip

the

4.5

MC

signal

to a

predetermined

limit.

•

Obviously, unless

the

"S"

curve is

shaped

as

recommended

by

the

set

manufacturer,

until

the

4.5

MC

point

is

exactly

at

the

center,

(using

the

4.5

MC

crystal)

and

unless

the

bias of

the

limiter

is

correctly

set

for

the

signal level applied_

to

the

grid,

amplitude

or

''buzz"

modulation

will

be

present

in

the

sound

output

circuits.

•

These

A.M.

rejection

circuits

have

simpler

counterparts

in

the

ratio

detector

gated

bAam

and

loclc-in oscillator

detectors

used

in

more

modern

intercarrier

receivers~

How-

ever,

it

is obvious

that

these

"simpler"

circuits

require

the

r;:amP.

care

in

alignment,

if

"buzz"

is

to

be

avoided

in

the

sound.

4.

R.F.

AND

CONVERTER

ALIGNMENT

R.F:

or

front

end

adjustments

can

be

made

in

the

same

manner

·as

for

the

separate

channel

type

of receiver.

•

5.

R.F.

OSCILLATOR

ALIGNMENT

The

R.F.

oscillator

has

little

effect

on

the

sound

signal

in

an

intercarrier

receiver.

For

this

reason,

one of

the

following

methods

will

be

found

most

suit.able- for

adjustment

.

of

the

local

oscillator frequency.

a.

Connect

t11e

output

cable of

the

E410C

to

the

antenna

input

connector

of

the

re-

ceiver

and

connect

the

receiver

response

cable across

the

video

detector

load

resistor.

Inject

a

marker

from

the

E200C

at

the

video

I.F.

frequency

by

loosely

coupling

near

the

input

to

the

first

I.F.

amplifier. Tlze alligator clips

at

the

free

end

of

tlze

marker

cable shQuld be clipped to tlze ch.assis

at

a

point

as close to

the

first

I.F.

grid as possible.

Set

the

frequency

of

the

E410C

to

the

PICTURE

frequency

of

the

channel

to

be

adjusted

and

reduce

the

sweep

width

of

the

E410C

output

to

nearly

zero.

Adjust

the

local

oscillator of

the

receiver

to

center

the

marker

on

the

screen

of

the

oscilloscope.

(The

fine

tuning

control

of

the

receiver

should

be

set

to

the

middle

of

its

range

in

making

this

adjustme11t).

Repeat

this

procedure

on

each

channel

in

the

order

recommended

by

the

set

manufacturer

and

make

the

necessary

adjustments

to

bring

the

marker

to

the

center

of

the

oscilloscope screen.

'

b.

Obtain

the

overall

response

curYe (E410C

output

connected

to

the

antenna

input

terminals

through

the

130

ohm

resistors,

and

the

dial

set

to

the

frequency

specified

i_n

the

instructions)

1

the

receiver

response

cable clips

connected

to

the

video

detector

load

resistor,

the

E200C

reconnected

to

the

marker

input

cOnnector

of

the

E410C.

Set

the

E200C

to

the

sou.nd carrier frequency of

the

.R.F.

channel

being

s,vept

by

31

•

I

the E410C.

Adjust

the

local oscillator so

that

the

marker

appears

at

the

10% shelf

on

the

response curve.

Repeat

this procedure for the receiver• channels as re~om-

mended

by

the

receiver service

manual.

Methods

of alignment of R.F. oscillators

vary

from one

manufacturer

to

another.

The

simplest,

most

frequently used

method

is

as

follo,vs:

'

(1)

The

receiver response cable of

the

E410C is connected across

the

discriminator

.

load

resistors.

(2)

The

output

cable of

tl1e

E410C is connected

to

the

antenna

terminals

?f

the

T.V.

receiver (using

the

impedance

matching

netw,ork of

the

130

ohm

resistors).

(3)-

The

nutnufacturer ,vill call for a

certain

sequence of ·check and:

adjustment

of the oscillator beginning with a certain chnnnel, with

the

remainder

of

the

cl1annels to be· s\vitched

as

specified.

The

instructions ,vill probably call for

the

0

:fine

tunini'

knob to be

set

to

mid

position,

as

each chanriel

is

aligned.

(

4)

The

dial

of

the

E410C is

set

to

the

soz1.nd

channel frequency of the first channel

to

be

aligned

..

(5)

(6)

..

H facilities for injection of l1igh frequency mark:ers is

not

available,

the

dial of

the

E410C

may

be

used

to

checlt

and

align

the

R.F,. oscillator.

With

the

tuning

dial

of

the

E410C

set

to

the

-proper

sound

channel

frequency a

properly

aligned

R.F.

oscillator

v-nll

produce a discri11iinator response ('tS'' curue) located 1iorizontall.y

at

t1ie

center

of

tJie

scope screen.

The

station signal,

if

available,

can

be

used

as

a

marker

as

explained on following

page.

When

checking

the

first channelt

if

the

discriminator

pattern

is

not

located

at

the

center

of

the

oscilloscope screen,

adjustment

of

the

approximate

oscillator

trimmer

is

made

to move

the

u9,, curve to the

center

of

the

oscilloscope screen

in

accordance with

the

manufacturer's

instructions.

(7)

The

remaining channels

are

aligned

in

a similar

manner.

'

NOTE:

.In

some cases

it

may

be necessary to

adjust

the

fine

tuning

control slightly

to

properly align

all

channels~

(1)

(2)

(3)

(4)

A

variation

of

the

above procedure is

as

follows:

.Connect a vacuum tube voltmeter such as Precision

Apparatus

acro~s

the

discrim

..

inator

load

resistor.

Connect

the

output

of

the

high

frequency signal

generator

to

the

antenna

terminals

of

the

receiver

under

test.·

The

dial

0£

the

-signal

generator

set

to

the

sound

frequency of

the

channel to

be

checked.

If

the

oscillator

is

properly

aligned, a

trial

adjustment

of

the

oscillator

trimmer

or

slug

will cause

the

VTVM

to

vary

from a negative voltage

reading

through

a zero

voltage

reading

and

then

to a positive voltage reading.

The

proper

adjustment

is

that

which will

result

in

a zero

reading

(

center

point

of discrim_inator response) .

NOTE:

If

the

oscillator

trimmers

or

slugs

are

rotated

too

much

two false zero readings

can

be obtained. A false zero

reading

falls outside

of

the

discimiuator response region.

A check

£or

the

proper

zero voltage adjustµtent•is

made

by

sliglit rotation of

the

trimmer

or

slug

to

the

left

and

right

of

the

zero voltage point.

If

the

oscillator

is

properly

adjusted

the

VTVM

will

indicate

a slight negative

or

positive voltage

as

the

slug

is

rotated

past

the

zero

point

changing polarity

as

it

passes through

the

zero point.

The

proper

zero

point

falls

in

behYeen

the

positive

and

negative

VTVM

readings.

82

•

'rhese

two

methods

are

identical

in

principle,

but

differ only

that

in

the

former a

swept

signal

and

visual indication is

made,

while in

the

latter

method

an

unmodulated

R.F.

signal

and

VTVM

are

used.

. . . .

It

must

also be indicated

that

for

this

adjustment

to be

made

c9rrectly,

the

sound

discriminator ~lignment

must

be

made

accurately

..

··The

actual

station

carriers

can

be

used

to

nutrk

the

sound

and

picture

frequencies,

as follows:

a.

Tune

in

a T.V.

station

on

the

receiver.

b. Disconnect

the

antenna

and

connect

the

E410C cable alligator clips

to

the

antenna

input

terminals.

c.

Reconnect

the

antenna

to

the

antenna

input

terminals

0£

the

T.V.

set

through

a

high resistance.

d.

Both

the

picture

and

sound

carrier

marlcers should

appear

on

the

trace.

The

sound

carrier

marker

becomes visible

as

the

fine

tuning

control

0£

the

receiver

is

adjusted

.

e

..

Run

the

sound

marker

into

the

sound

trap

by

adjustment

of

the

fine

tuning

control.

The

marli::er will

disappear

in

the

bottom

of

the

dip caused by

the

sound

trap,

and

will

reappear

on

either

side as

the

fine

tuning

control is varied.

When

the

sound

marlter

.disappears

in

the

sound

trap,

the

picture

marlter

should

appear

half

,yay

up

the

curve.

If

it

does

not

appear

.half way

up

on

the

curve,

the

R.F. coils should

be

adjusted

as required.

If

these

adjustments

cause a dip,

h11mp

or

slope

to

appear

along

the

top of

the

overall response curve,

adjustments

must

be

made

to

obtain

the

best

possible response curve

under

the

conditions of tube

and

component taler~

ances

0£

the

particular

receiver.

(This

procedure for insertion of

markers

by

using

the

actual

transmitted

signal is

an

excellent way of checking

the

receiver-oscillator

alignment itself.)

The

above

method

0£

front-end

alignment

adjustment

is satisfactory for

routine

front

end

alignment. Ho,vever,

if

alignment

of

the

front

end

itself is

desired-the

follo,Ying procedure should be adopted:

TO

VERT.

INPUT

OF

SCOPE

TO

HORIZ.

INPUT

Of

SCOPE

.

,

E-410C.

• -

-

R.f.

OUTPUT

CABlE -

•

.

Fig. 28

RF SECTION

OF RECEIVER

RECEIVER

RESPONSE

CABLE

TAKE-

OFF

POINT

NT

ENO

OF

FRO

(1) Connect

the

E410C

output

cable

to

the

receiver

antenna

terminals

through

the

matching

network consisting

of

the

two 130

ohm

resistors.

(2) Connect

the

receiver response cable

to

the take~off

point

in

the

converter circuit

as

described

in

.

the

manufacturer's

alignment

•instructions. •

(3)

Set

the

R.F.

and/or

I.F.

Bias

using a Precision

Apparatus

VTVM

to

obtain

the

bias voltage recommended

by

the

manufacturer.

(4)

Set

the

E410C

and

the

T.V

..

set

channel

selector to

the

frequency

0£

the

first chan-

nel

to

be

checked (as directed

by

the

set

manufacturer).

33

•

' -

(5) In

most

cases a broad

band

response curve (similar

to

that

of

Figure

29) ,vill·

·•,•·.

appear

on

the

oscilloscope trace.

(6) As

in

previous response checks,

an

accurate

marker

should

be

used

Qto

indicate

the

picture

carrier

point

and

the

sound

carrier

point

on

the

response curve.

(The

Precision

Apparatus

E200C ,vhich produces

fundamental

frequencies

up

to··110

MC

and

up

to

220

MC

on

its

second

harmonic

band

is

an

excellent

marker

generator

for

these

high

frequencies.

In

the

ideal case

the

markers

would

appear

as

shown

•

PICTURE

C.iAIUER

MARK£R

•

Fig.

29

•

in

the

figure.

In

practice

applications, ho,vever1

there

may

be considerable differ-

ence

in

the

shape

and

band,vidth of

the

R.F

..

video

channel

response curve. Again

reference

must

be

made

to

the

manufacturer's

alignment

notes

for

the

wave

shape

and

bandwidth

of

the

particular

front

end

being checked.

Each

channel

is checked in

similar

fashion2 (E410C

dial

and

receiver

channel

selector

set

to

the

desired

channel),

and

the

appropriate

inductance

and

capacitance

adjustments

are

made

if

required

to

correct

the

response curve shape, as described

in

the

manufacturer*s

alignment

procedure.

It

should

be

noted

that

unless a

marker

generator

such

as

the

E200C is used

it

may

be impossible

to

perform

the

second

method

since

most

other

marker

generators

are

not

sufficiently

high

in

frequency

to

mark

the

sound frequency

at

the

higher

channels. An

alternative

method

is

that

of

the

first procedure, except tha·t

the

T.V.

station

signal is used to

mark

the

frequency

curve.

In

this procedure,

the

antenna

is

connected

to

the

antenna

input

connector

through

a high resistance

to

attenuate

the

incoming signal

and

avoid

overloading of

the

response curve.

NOTE

re:

COLOR

T.V.

AT.JGNMENT

No

specific

alignment

instructions

have

been included

in

this

manual

for color

T.V.

receivers.

The

manufacturer's

instructions

should

be followed.

Since

the

bandwith

of

the

color

T.V~

set

must

be

greater

than

that

of

the

conventional black

and

white

set.

the

only

practical

way

of achieving

this

extra

,vide

bandwidth

is

through

·sweep gen-

erator

alignment.

It

niust be remembered tliat

when

the

manufacturer calls for connec-

tion front tlie vertical scope

input

to a particular point on tlte receiver, the•receiuer

response cable

of

the E410C is connected to

that

pnint

on

tlie receiver., since

the

vertical

scope cable of

the

E410C is

to

be permanentl)' cnnnected to

the

vertical

input

of

the

oscilloscope.

34

-

··

VHI.

SPEC~L

FUNCTIONS

AND

PROCEDURES

•

1.-

INTERNAL

MARKER

OSCILLATOR

It

should

be

noted

that

a 4.5

MC

crystal

is

provided

with

each

model E410C sweep

generator

and'

marker

adder.

While

the

primary

purpose

of

this

crystal

is

in

the

align-

ment

of

intercarrier

sound stages

it

can

also be

used

for

the

marking

of

the

sound

and

picture

positions on

I.F.

response curves.

(The

marker

and

sound

positions

are

4.5

MC

apart.

By

beating

the

crystal

against

the

output

of

the

marker

generator

in

the

.E4·10C

marker

adder

circuit, "pips,,, ,vill

appear

at

the

desired frequency.

The

marker

generator

should

be

set

4.5

MC

below

the

lowest freqt1ency desired.)

A visual

method

by

,vhich

the

calibration of

an

external

marker

generator

is

accom-

plished is as follows:

Depending

on

the

frequencies

at

which

the

generator is

to

be

calibrated

the

follow-

ing

crystals

should

be obtained: 10 MC) 5 MC, 1 MC.

The

crystal

should be

mounted

in

a

type

''Fr-284''

holder)

..

A..

CRYSTAL

CALIBRATION

OF

MODEL

E200C

(or

equivalent

stable

A.M. generator)

..

(1) Connect

the

E410C, E200Ci

crystal

diode

and

oscilloscope (Precision

Appara~s

S-55

or

ES-550B) as indicated

in

Figure

30.

(2) Connect

the

oscilloscope vertical cable

to

the

marker

input

connector

on

the

E410C

..

HlGH

E-2000

""

OUTPUT

___

...,

•

SCOPE

:~1

...

,

...

-@

0

--

.-

....

0

• • • ,

__

0

CONNECTOR

y 0

...

111,.

""""

...

0

(3)

(4)

(5)

(6)

(7)

/

E410C RECEIVER

OUTPUT CABLE

1N48

GERW.A.NIUM

DIODE

GHQ

Fig,

30

0

PLUG

Ht

CRYSTAL

'

~1ARKER

INPUT

CABLE

E410C SCOPE

VERTICAL CABLE

Connect

the

receiver

output

cable tp

the

high

output

connector of

the

E200C.

Connect

the

red

banana

plug

and

the

red

alligator clip

to

one

side

of

the

crystal

diode. Connect

the

black

banana

plug

and

the

black alligat.or clip

to

the

vertical

ground

connector

of

the

scope.

Connect

the

free

end

of

the

diode

to

the

vertical

input

connector of

the

oscilloscope.

Adjust

the

E410C to

band

A

and

rotate

the

s,Y"eep

width

control

fully

counter-

clockwise. -

Insert

a

crystal

of

the

proper

frequency (10

MC),

for example,

into

the

crystal

socket of

the

E410C

..

Crystal

frequencies

of

10, 20, 30, 40i 50, etc.

MC

,vill

appear

at

the

output

of

the

crystal

oscillator

and

will be

fed

to

the

input

of

the

crystal

diode.

35

•

I

Dynascan Corporation E410C User manual

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