JVC KD-A66 Manuale utente

MODEL

KD-A66

A/B/C/E/J/U

STEREO

CASSETTE

DECK

No.

4193

June

1980

No.

4193

KD-A66A/B/C/E/J/U

|

Contents

Page

Specifications...

0...

ee

es

2

FOQtUFOS

ape

cnt

id

ean

erate

bos

ah

A

a

ei

ee

ea

ee

3

Controls

and

Connections...

......-----00

ee ee

eee

3

Main

Parts

Location...

......

2.002:

eee

ee

eee

4

Description

on

New

Technology.

..........--+-+----

5

Maintenance.

.......

00

eee

ee

eee

10

Removal

of

the

Main

Parts

......-...0202000000

10

Main

Adjustments

........

200002

eee

ee

13

Block

Diagram

2.0...

et

20

Instruction

of

ICs

2...

ee

22

Standard

Schematic

Diagram

(Main

Amp

Circuit)...

....0..0

0000.

eee

23

(Mechanical

Control

Circuit)...

.........2005.

24

(Computer

Circuit)...

2...

2.0.00

ce

eee

oe

tess

25

Specifications

Type

:

Component

stereo

cassette

deck

Track

system

:

4-track,

2-channel

Tape

speed

:

1-7/8

inch/sec

(4.8

cm/sec)

Frequency

response

:

(-20

VU

recording)

Metal

tape

*1

515

—

18,000Hz

25

—

16,000Hz

(+3dB)

SA/Chrome

tape

“2

15—

18,000Hz

25

—

16,000Hz

(+3dB)

SF/Normal

tape

*~3

15

—

17,000Hz

25

—

15,000Hz

(+3dB)

(O

VU

recording)

Metal

tape

SA/Chrome

tape

SF/Normal

tape

25

—

12,500Hz

(+3dB)

25

—.8,000Hz

(+3dB)

25

—8,000Hz

(+3dB)

Frequency

response

when

using

the

computer

B.E.S.T.

tuning

system

(~20

VU

recording)

Metal

tape

SA/Chrome

tape

SF/Normal

tape

40

—

12,500Hz

(+1dB)

40

—

12,500Hz

(+1dB)

40

—

12,500Hz

(+1dB)

Those

values

are

almost

the

same

for

all

types

of

tapes

when

the

computer

B.E.S.T.

tuning

system

is

used.

Note:

*1.....

SCOTCH

METAFINE

or

Equivalent

AD,

TDK

SA

or

Equivalent

Ec

ie

MAXELL

UD

or

Equivalent

S/N

ratio

:

60dB

(from

peak

level,

weighted,

Metal

tape)

The

S/N

is

improved

by

5dB

at

1

kHz

and

by

10dB

above

5kHz

with

ANRS

on.

(DIN

45

500

weighted)

Effect

of

Super

ANRS

:

(Normal

tape)

Improvement

of

S/N:

the

same

as

with

ANRS

Improvement

of

frequency

response:

0

VU

recording;

6dB

at

10kHz

+5

VU

recording;

12dB

at

10kHz

Improvement

of

distortion:

0

VU

recording;

3%

or

less

at

10KHz

+5

VU

recording;

3%

or

less

at

10kHz

Wow

and

flutter

:

0.04%

(WRMS),

0.14%

(DIN

45

500)

Page

Wiring.

(1):

(3)

sins

ON

BS

ee

ea

ee ae

VS

26

~28

Enclosure

Assembly

and

Electrical

Parts

List

......

30

Enclosure

Assembly

and

Electrical

Parts

...........

33

Mechanical

Component

Parts.............0.005-

34

Mechanical

Component

Parts

List.............-

35

Main

Amp

P.W.

Board

Parts...

.....

2.000002

ee

37

Computer

P.W.B.,

Mechanical

Control

P.W.B........

38

Main

Amp

P.W.

Board

Parts

List...............

39

Computer

P.W.

Board

Parts

List..............4.

42

Mecha

Control

P.W.

Board

Parts...

..........0055

45

Mecha

Control

P.W.

Board

Parts

List............-

46

Other

P.W.

Board

Parts...

0...

0.

cee

ee

es

47

Other

P.W.

Board

Parts

List.......-....000005

48

Packing,

Packing

Material

List,

Accessories..........

49

:

65dB

(1kHz)

K3;0.4%,

THD;

1.0%

(metal

tape,

1kHz

OVU)

Crosstalk

Harmonic

distortion

:

Bias

:

AC

bias

Erasure

:

AC

erasure

Heads

:

2SA

(Sen-Alloy)

heads

X-cut

head

for

recording

and

playback

2-Gap

head

for

erasing

:

Electronic

governed

DC

motor

(for

Capstan)

DC

motor

(for

Reel)

:

85

sec.

with

C-60

cassette

:

85

sec.

with

C-60

cassette

:

18

ICs,

77

transistors,

1

FET

52

diodes,

12

LEDs

Motors

Fast

forward

time

Rewind

time

Semiconductors

Input

terminals

Mic

jack

x

2

;

Max.

sensitivity;

0.2mV

(-72dBs)

Matching

impedance;

6002.

~

10k92

Input

jack

x

2;

Min.

input

level;

80mV

(-20cBs)

Input

impedance;

100kQ

Output

terminals

Output

jack

x

2.

;

Output

level;

0

~

500mV

Output

impedance;

5kQ2

Phones

jack

x

1;

Output

level;

0

~

0.5mV

Matching

impedance;

BQ

~

1kQ

:

AC

240V,

50Hz

(KD-A66A)

AC

120V,

60Hz

(KD-A66C/J)

AC

240/220/120V,

50/60Hz

(KD-A66B/E)

AC

240/220/120/100V,

50/60Hz

(KD-A66U)

Power

consumption

:

30W

Power

requirement

Dimensions

:

17-3/4''(450mm)W

4-5/8"

(118mm)H

13”

(331mm)D

(with

feet,

buttons,

switches)

Weight

:

17.4

Ibs

(7.9

kg)

Design

and

specifications

subject

to

change

without

notice.

Features

1.

Controls

and

Connections

»

@

0

12)

®

.

X-cut

SA

(SEN-ALLOY)

Built-in

computer

B.E.S.T.

Tuning

System

for

auto-

matic

adjustment

of

Bias,

Equalization

and

Sensitivity

of

Tape.

.

Metal

tape

compatibility

having

4

tape

select

positions.

.

Full-logic

control

operation

with

2

motor

ID

(Inde-

pendent

Drive)

mechanism.

record/play

head

for

an

improved

frequency

response

over

Permalloy

yet

as

durable

as

ferrite.

_

SA

(SEN-ALLOY)

erase

head

for

perfect

compatibility

with

Metal

Tape.

.

LED

indication

for

cassette

operation

buttons

(REC,

PLAY,

PAUSE)

light

for

the

respective

operation

mode

so as

to

make

checking

easier.

oe

989

10.

11.

12.

KD-A66A/B/C/E/J/U

ANRS,

and

Super

ANRS

for.decreasing

hiss-noise

and

improving

linearity

at

high

frequency.

.

5

LED

multi-peak

level

indicators

for

easy

check

of

the

recording

level.

Continuous

TIMER

STAND-BY

mechanism

for

record-

ing

when

you

are

not

at

home

using

the

REC-OFF-

PLAY

select

switch.

REC

MUTE

button

for

making

a

non-recorded

section

on

the

tape

program.

Memory

switch

for

listening

to

the

same

program

repeatedly.

;

Remote

control

terminal

(R-50E

optional)

(Cramer

Stance

||

PHONES)

cca)

ce

hd

POWER

switch

VU

meter

(left

channel)

VU

meter

(right

channel)

@

Indicators

(see

to

page

4)

@8E268

6600000

Computer

START

button

Computer

PRESET

button

Cassette

holder

Tape

COUNTER/counter

reset

button

MEMORY/AUTO

REW

switch

TIMER

STANDBY

switch

Headphone

jack

[PHONES]

Microphone

jack

(Left

channel)

[MIC-L]

Microphone

jack

(right

channel)

[MIC-R]

ANRS

switch

TAPE

SELECT

switch

INPUT

LEVEL

controls

forward

knob

—

left

channel

rearward

knob

—

right

channel

7]

®

8066

e

®

OUTPUT

LEVEL

control

Cassette

operation

button

<<

>

REW

(Rewind)

button

>>

FF

(fast-forward)

button

>

PLAY

button

a

STOP

button

Oo

REC

(recording)

button

«©

=~

PAUSE

button

REC

MUTE

button

EJECT

button

Voltage

selector

(KD-A66B/C/E/J/U)

Remote

control

socket

LINE

IN

terminals

LINE

OUT

terminals.

Power

cord

No.

4193

KD-A66A/B/C/E/J/U

Indicators

No.

4193

Super

ANRS

indicator

(The

LED

lights

when

super

ANRS

or

ANRS

is

ON)

ANRS

indicator

RUN

(wink)/READY

(glow)

indicator

ERROR

(wink)/PRESET

(glow)

indicator

Multi-peak

level

indicator

@OS0

©

@

Front

panel

assembly

@

DC

solenoid

®

Reel

motor

@

Output

level

control

©

Input

level

contro!

@

VU

meter

(right

channel)

@

VU

meter

(left

channel)

@

Meter

cover

@

Remote

bar

(for

power

switch)

@

Computer

P.W.

Board

assembly

@®

Power

switch

@®

Power

transformer

®

Power

supply

integrant

circuit

P.W.B

assembly

@®

Remote

control

socket

@®

jack

assembly

(Mechanical

parts)

®

Switch

holder

(left

switch)

@

Supply

reel

assembly

@®

Idler

assembly

@®

Ree!

motor

pully

@

Take-up

reel

assembly

@

Connector

wire

(for

slide

base)

@

Counter

belt

@®

Slide

base

assembly

@

Erase

head

@®

REC/PB

head

@

Pinch

roller

assembly

@

Capstan

KD-A66A/B/C/E/J/U

Description

on

New

Technology

Computer

B.E.S.T.

System

Introduction

The

B.E.S.T.

(Bias

Equalizer

Sensitivity

Tuning)

system

which

is

employed

in

the

KD-A66

is

basically

the

same

as

the

preceding

KD-A8

version

and

has

also

been

provided

with

various

improvements

for

an

enhanced

performance.

The

B.E.S.T.

system

employs

a

microcomputer

for

the

purpose

of

setting

the

proper

optimum

bias

current

and

sensitivity

for

tape.

1.

Bias

As

seen

in

Fig.

1

(the

relationship

between

distortion

rate

and

bias

current

at

the

1

kHz

to

7

kHz

signals),

the

output

level

decreases

when

a

larger

bias

current

is

ap-

plied.

In

this

case

especially,

the

7

kHz

signal

is

sharply

attenuated.

Further,

when

the

bias

current

is

decreased,

the

three-

dimensional

distortion

increases.

Accordingly,

the

bias

current

is

an

important

factor

for

determining

the

frequency

response

and

the

distortion

rate.

It

is

therefore

desirable

that

an

optimum

bias

current

is

set

for

each

tape.

—

Bias

current

(uA)

200

300

400

500

600

700 800

o

=z

D

1KHz

hi

2

Qa

i]

t=

3

i

O

10F

'

T

Set

bias

current

value

;

T7KHz

a3

|

&

2

64

\

£

\

'

c

°F

vot

Third

harmonic

distor-

S44

ar

tion

at

333

Hz

es.

Xe

(250mW/level)

-

|

NU

2

f----4---¥,

Third

harmonic

distor-

QO

24

o’

are

Se

tion

at

1

kHz

Toa

S160

mWitevel)

Fig.

1

2.

Equalizer

As

seen

in

Fig.

2

(with

each

tape

having

its

optimum

bias

current

set),

this

bias

current

is

determined

by

tak-

ing

into

account

the

high-band

molecular

character-

istic

and

distortion

rate

of

the

particular

tape.

Equali-

zation

level

must

then

be

set

to

obtain

a

flat

molecular

START

16sec

Far:

l2sec

REC-*

Blank

Marker

Approx.

|.2sec

Point

to

which

the

tape

is

rewound

Marker

Point

to

which

the

tape

is

rewound

Bias

sweep

spot

signal

\

characteristic

corresponding

to

that

bias

current.

Until

now,

the

equalization

level

has

been

determined

by

ear

and

an

accurate

tuning

can

only

be

performed

by

experience.

With

this

tuning

system,

the

equalization

level

is

auto-

matically

set

by

a

microcomputer.

Frequency

Distribution

o

mo}

Ovseeeee

denotes

the

type

of

the

tape.

3

5

6

|

NORM

CrOs

Fe-Cr

ax

STD.

UD

STD.

SA

STD

Duad

3

6

4

|

(MAXCE)

(10.4)

(SONY)

eS

a8

2

3

o

:

20

o

=

0

8

-

Boece

to

£

fo}

2

sseecee

eeco00o

oo

ng

Ss

eo

t

Zo

o800000

:

=

$

-4

oe

°

Fis

x

§

xo

°

es

1

:

Fig.

2

Sensitivity

In

tapes,

the

recording

and

reproduction

levels

do

not

necessarily

coincide

with

each

other.

The

difference

between

the

recording

and

reproduction

levels

appears

as

a

beat

in

the

frequency

response

of

a

noise

reduction

circuit

such

as

the

ANRS

circuit,

the

Super

ANRS

circuit,

etc.

In

this

tuning

system,

the

difference

between

these

levels

is

limited

within

1

dB.

Features:

1.

Automatic

setting

of

the

optimum

bias

current

for

the

tape.

2.

Automatic

setting

of

the

level

difference

to

within

+1

dB,

in

the

case

of

10

kHz

high-band

frequency

which

tends

to

differ

between

the

recording

and

reproduction

levels.

3.

Automatic

setting

of

the

tape

sensitivity

to

within

a

+1

dB

error

by

the

ANRS

circuit.

4.

For

tapes

which

cannot

be

automatically

adjusted,

its

sensitivity

is

indicated,

thus

permitting

normal

recording

in

the

state

in

which

respective

values

have

been

preset.

Frequency

characteristic

sensitivity

sweep

spot

signal

L6sec

\1.2sec

Marker

Approx.

|.5sec

Play

REC

—

Blank

~+—

REW

STOP

(the

tape

is

rewound

to

the

vicinity

ii

WIA

of

its

starting

position.)

PLAY

—

-

.

END

+

REW

Fig.

3

No.

4193

KD-A66A/B/C/E/J/U

Operation

The

operation

is

described

in

accordance

with

Fig.

3

(opera-

tional

timing

chart).

1.

No.

4193

Press

the

START

button.

At

this

time,

the

READY

LED

in

the

display

section

flickers,

indicating

that

the

computer

is

in

operation.

The

tape

is

rapidly

fed

at

1.6

sec

to

avoid

the

use

of

the

leader

tape

section.

The

recorder

enters

the

recording

mode.

In

this

mode,

a

blank

recording

(no-signal

recording)

is

performed

for

2.8

sec

to

stabilize

the

mechanical

and

electrical

systems.

Subsequently,

two

marker

signals

and

eight

pairs

of

1

and

7

kHz

test

signals

are

recorded.

At

this

time,

the

bias

current

is

varied

8

steps

every

60

msec

by

+10%

to

-30%

more

than

the

preset

value.

(The

bias

current,

equalization

level

and

tape

sensitivi-

ty

values

are

preset,

each

determined

by

using

a

stand-

ard

tape.)

(Fig.

4)

Preset

value

Bias

current

8

step

bias

current

variations

ome

Markers

ms

1kHz

7

kHz

1

kHz

AN

NK

Ae

Pe

Z

Tone

&

ABBHHEE

Anew

e

eG

ZEZeZceZes

J

Markers

ze

——

1kHz

7

kHz

1121314415

|6|7

60

msec

NY

ON

NNN

REC

Set

point

Fig.

4

The

tape

is

rewound

to

return

to

the

position

at

the

1.6

sec

lapse

point

from

the

beginning

of

the

recording.

Data

on

the

tape

is

reproduced,

and

the

reproduction

levels

of

the

1

and

7

kHz

test

signals

are

compared

in

order

to

properly

determine

their

coinciding

step.

The

microcomputer

detects

these

coincident

steps.

At

this

time,

the

recorder

initiates

recording

and

per-

forms

a

blank

recording

for

2.8

sec.

Subsequently,

the

recorder

records

the

markers,

and

enters

the

12.5

kHz

signal

recording

state

after

recording

the

1

kHz

refer-

ence

level,

and

increasingly

varies

the

equalization

level

of

the

right

channel

by

8

steps

very

60

msec.

Further,

after

recording

the

1

kHz

reference

signal

of

the

left

channel,

the

recorder

increasingly

varies

the

equalization

level.

Next,

to

adjust

the

tape

sensitivity,

the

recorder

increasingly

varies

the

1

kHz

recording

level

by

8

steps

every

60

msec.

The

difference

between

the

smallest

and

largest

levels

is

+4

dB.

(Fig.

5)

As

shown

in

Fig.

2,

the

tape

is

rewound

to

the

position

at

the

1.5

sec

lapse

from

the

beginning

of

recording;

see

item

6.

Right

equalizer

Left

equalizer

Tape

sensitivity

Markers

tight

equalizer

Left

equalizer

Markers

aire!

Set

point

The

recorder

enters

the

reproduction

mode,

and

the

microcomputer

first

compares

the

reproduction

levels

of

the

1

kHz

reference

signal

and

the

12.5

kHz

signal

of

the

right

channel.

In

recording,

since

the

12.5

kHz

signal

is

increasingly

varied

by

the

right

equalizer,

its

reproduction

level

will

coincide

with

that

of

the

1

kHz

reference

signal.

Sub-

sequent

to

storing

this

coincident

point,

the

same

operation

is

also

performed

on

the

left

channel.

Next,

the

tape

sensitivity

is

adjusted.

Prior

to

this,

the

recorder

stores

the

reproduction

level

of

the

1

kHz

reference

signal

of

the

right

channel

during

recording

(item

6),

and

during

reproducing,

seeks

its

coincident

point

with

the

8-step

level

varied

tape

sensitivity

adjust-

ing

signal.

Is

the

SERVICE

switch

at

thé

OFF

position?

Setting

of

preset

vaiues

and

auto

set

values

's

the

START

switch

at

the

ON

position?

Setting

of

frequency

response

sensitivity

in

this

ror

the

first?

Rewinding

the

tape

to

its

starting

position

Setting

of

auto

set

values

|

Fig.

6

9.

Upon

completion

of

tuning

the

equalizer

and

the

tape

sensitivity

(item

8),

the

tape

is

rewound

to

return

to

the

position

as

described

in

item

1.

Then,

the

flickering

READY

LED

lights

continuously.

The

above-mentioned

operation

is

shown

in

Fig.

6.

The

basic

operation

is

as

previously

described.

In

addition,

the

microcomputer

is

provided

for

the

functioning

of

the

tape

deck.

Upon

application

of

power,

the

microcomputer

is

auto-

matically

reset,

thus

resulting

in

a

temporary

stoppage

of

all

output.

SERVICE

switch

This

switch

is

used

to

adjust

the

tape

deck.

The

microcomputer

with

7

adjustment

program

checks

the

generation

of

the

test

signals,

the

variation

of

the

bias

cur-

rent,

the

variation

of

the

equalization

level,

the

variation

of

the

tape

sensitivity,

the

operation

of

the

electronic

mecha-

nism,

and

the

like.

When

the

SERVICE

switch

is

at

the

OFF

position,

the

microcomputer

confirms

that

the

B.E.S.T.

system

is

func-

tioning.

At

this

time,

the

microcomputer

emits

those

auto

set

values

when

the

B.E.S.T.

system

completes

operation

and

emits

the

preset

values

even

if

an

error

occurs

during

the

operation.

Thus,

even

when

the

auto

setting

of

the

res-

pective

values

is

impossible,

normal

recording

is

possible

since

the

preset

values

are

emitted.

Subsequently,

the

microcomputer

waits

for

the

START

switch

to

be

pressed.

When

this

switch

is

pressed,

the

micro-

computer

sets

bias

current,

equalization

level

and

tape

sen-

sitivity

values.

In

this

process,

when

auto

setting

is

impossible,

the

micro-

computer

returns

to

the

bias

setting

mode

to

re-tune.

At

this

time,

when

an

error

recurs,

the

red

PRESET

LED

flick-

ers

and

the

preset

values

are

emitted.

In

addition,

irrespective

of

presence

or

absence

of

error,

the

tape

is

rewound

to

its

starting

position.

As

a

result

of

this,

the

tape

is

effectively

used.

In

normal

auto

setting

of

the

respective

values,

the

rewinding

time

is

about

25

sec.

Operating

Principle

of

Respective

Sections

KD-A66A/B/C/E/J/U

1.

Setting

of

bias

current

Fig.

7

represents

the

bias

current

varying

circuit

em-

ployed

in

the

KD-A66.

The

bias

oscillation

circuit

consisting

of

transistors

X701

and

X702

supplies

current

to

the

erase

head

and

also

activates

the

bias

amplifier

consisting

of

transistors

X703

and

X704.

As

the

supply

voltage

for

this

bias

amplifier

is

changed

in

8

steps

by

a

control

signal

from

the

microcomputer,

the

bias

current

is

changed

in

8

stpes.

When

the

binary

control

signal

from

pins

2,

3

and

4

of

microcomputer

(ICKO1)

is

applied

to

IC701

which

includes

8

electronic

ON/OFF

switches

of

8

circuits,

any

one

circuit

alone

is

turned

on.

At

this

point,

the

base

current

passes

across

a

specific

one

of

transistors

X709

—

X716

turning

it

on.

Concerning

transistor

X708

which

controls

the

supply

voltage

for

the

bias

amplifier,

its

base

voltage

is

deter-

mined

by

a

divided

voltage

by

R728

and

the

associated

collector

resistance

of

X709

to

X716.

The

bias

oscillation

circuit,

which

is

turned

on/off

by

the

BMUTE

signal

from

304

on

the

computer

circuit

board,

is

also

turned

on/off

by

the

NSTOP

signal

(the

control

signal

of

the

brake

and

solenoid)

from

512

on

the

same

board

when

stopping

the

bias

oscillator

circuit

operation

during

the

PAUSE

mode.

+VCCRI

TO

HEAD

Equalization

level

change-over

signal

Tape

sensitivity

change-over

signal

Fig.

8

2.

Setting

of

equalization

level

and

tape

sensitivity

Fig.

8

represents

the

recording

amplifier

section

employed

in

the

KD-A66.

The

input

signal

is

attenuated

by

resistor

RO

and

any

of

resistors

R1

—

R16

and

entered

into

the

specific

transistor.

At

this

time,

a

tape

sensitivity

select

signal

emitted

from

the

microcomputer

causes

the

respective

resistor

in

the

group

of

R1

—

R16

to

be

grounded,

thus

determining

the

attenuation

level.

The

select

signal

is

transmitted

in

the

form

of

4

binary

bits

and

converted

into

decimal

bits.

In

addition,

a

CMOS

IC

incorporat-

ing

analog

switches

is

used

in

the

select

switch

unit

to

protect

the

audio

signal

against

distortion.

This

select

switch

unit

permits

the

change

in

recording

level

of

+4

dB.

No.

4193

KD-A66A/B/C/E/J/U

No.

4193

The

LC

resonance

peaking

circuit

mounted

in

parallel

with

the

emitter

resistor

of

the

recording

amplifier

transistor

boosts

the

high

frequency

of

the

recording

amplifier

transistor.

With

a

normal

tape,

the

output

level

of

a

10

kHz

signal

is

higher

by

about

9

dB

than

that

of

a

1

kHz

signal.

To

avoid

this

problem,

the

selection

of

the

capacitor

in

the

peaking

circuit

is

performed

to

vary

the

compensa-

tion

of

high

frequencies.

In

this

case,

the

microcom-

puter

emits

a

3

binary

bit

signal,

decodes

it

in

8

steps

and

switches

the

appropriate

analog

switch

in

the

CMOS

IC.

Thus,

the

recording

level

is

selected

in

the

range

of

+4

dB.

Fig.

9

Peak

hold

A/D

converting

circuit

In

the

KD-A66,

a

12.5

KHz

frequency

is

selected

as

the

equalizer

tuning

frequency

to

improve

high

band

frequency

response.

In

a

cassette

tape

deck

with

high

frequencies,

the

changes

in

levels

such

as

are

caused

by

dropout,

etc.

are

enlarged

due

to

the

base

material

of

the

cassette

tape

and/or

the

wound

state

of

the

cassette

tape.

If

the

optimim

state

is

decided

by

the

reproduc-

tion

level

such

as

in

the

B.E.S.T.

system,

this

level

change

causes

incorrect

setting

of

the

respective

values.

To

avoid

this

problem

in

the

KD-A66,

a

peak

hold

A/D

converter

has

been

developed

by

the

combination

of

a

peak

hold

circuit

and

a

charge/discharge:

circuit.

The

peak

hold

A/D

converting

circuit

permits

stable

level

detection

even

against

high

frequency

dropout.

Block

diagram

is

shown

in

Fig.

9

and

timing

chart

in

Fig.

10.

The

input

signal

is

classified

into

a

left

or

right

channel

signal

in

IC801

by

the

Lch

signal

from

the

microcom-

puter,

amplified

by

1C802A

and

entered

into

the

peak

hold

circuit

consisting

of

1C802B,

C802,

D802

and

X805,

which

in

turn

detects

the

negative

component

of

the

input

signal

accumulating

at

capacitor

C802.

In

the

KD-A66,

upon

completion

of

the

40

msec

oper-

ation

of

the

peak

hold

circuit,

$3

and

S4

in

1C801

are

turned

on

by

the

ADC

signal

from

the

microcomputer.

Since

$3

functions

to

apply

+5V

to

the

positive

input

side

of

1C802B,

the

output

of

1C802B

is

clipped

to

+5V

and

the

loop

in

the

peak

hold

circuit

is

opened

by

diode

D802.

At

the

same

time

S4

is

turned

on

and

capacitor

C802

is

charged

from

the

constant

current

source

I1.

Since

a

constant

current

is

supplied

to

this

capacitor,

the

volt-

age

in

it

linearly

increases

in

the

form

of

V=I1

x

Time/c

+

Vo

(initia!

voltage).

Since

capacitor

C802

has

been

supplied

with

the

negative

component

of

the

input

signal,

when

the

volt-

age

in

it

rises

with

the

constant

current

charge,

IC803A

detects

the

moment

that

this

voltage

exceeds

OV,

and

transmits

that

detection

signal

as

an

ADT

signal

to

the

microcomputer.

The

microcomputer

measures

the

time

from

when

the

40

msec

peak

hold

operation

is

completed

to

when

the

above

voltage

exceeds

OV,

to

measure

the

signal

level.

Fig.

10

is

the

timing

chart.

Here

the

input

signal

is

sub-

ject

to

peak

holding

during

the

40

msec

period

and

the

constant

current

discharge

is

performed

and

the

state

of

OV

excess

is

shown.

AD1

is

a

normal

signal,

but

this

indicates

that

stable

measuring

is

possible

should

level

change

(decrease)

occur

halfway

as

in

AD2

and

AD3.

WN

A

ADC

Teal

fea

AD3

]

x805

——

:

+

<--|

ae

/

ft

|

Marker

signal

detection

When

recording

while

tuning

the

bias

current,

equaliza-

tion

level

and

tape

sensitivity,

marker

signals

first

enter

as

shown

in

Figs

4

and

5.

A

40

msec

signal

of

1

kHz

+50

dB

is

recorded

two

time

as

the

marker

signals

with

a

40

msec

blank

between.

In

the

B.E.S.T.

system,

when

the

tape

is

rewound

after

recording

the

test

signals,

it

returns

to

its

starting

posi-

tion

while

counting

the

pulses

from

the

tape

counter.

This

counting

is

not

as

accurate

as

when

locating

a

60

msec

signal.

For

more

accurate

counting,

the

deck

waits

for

the

said

marker

signals

to

appear

in

the

repro-

duction

state

after

rewinding

the

tape.

After

the

input

signal

is

amplified

by

1C802A

in

Fig.

9,

it

is

compared

with

-0.5V

of

IC803B

in

Fig.

5.

When

this

signal

is

entered,

the

output

from

IC803B

is

inverted

from

+5V

to

-5V,

thus

transmitting

the

arrival

of

the

marker

signals

to

the

microcomputer.

After

detecting

the

marker

signals,

the

microcomputer

chekcs

their

pattern

to

discriminate

the

test

signals,

thereby

preventing

faulty

operation

due

to

external

noise

and

ensuring

accurate

signal

location.

To

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Fig.

11

Microcomputer

In

the

KD-A66,

the

tuning

function

is

controlled

by

the

42-pin

LSI

microcomputer

which

stores

instructions

of

about

2000

steps

and

processes

normal

instructions

at

10

msec.

The

connection

diagram

is

shown

in

Fig.

11.

In

addition,

its

incorporated

timer

controls

the

timing

of

the

entire

deck.

The

process

is

performed

in

the

P-channel

MOSFET

and

the

output

is

used

in

the

form

of

an

open

drain

type

pull-down.

The

clock

circuit

stably

operates

because

it

consists

of

an

LC

resonance

circuit.

Since

the

microcomputer

is

provided

with

an

interruption

function,

the

pulse

from

the

tape

counter

is

counted

with

interruption.

Auto-stop

The

rotation

pulse

signal

from

the

Hall

IC

is

waveform

rectified

and

differentiated

at

its

leading

and

trailing

edges.

Then,

the

monostabie

multiple

circuit

generates

a

pulse

of

about

20

msec

which

is

in

turn

applied

to

the

interrupt

terminal

INT

of

the

microcomputer.

The

microcomputer

detects

the

tape

position

by

the

rotation

pulse

signal

and

also

generates

an

auto-stop

signal

if

no

signal

is

applied

for 1.5

sec

or

more.

Auto-rewind

circuit

In

the

KD-A66,

when

an

auto-stop

signal

is

emitted

from

the

microcomputer

(ICKOI)

at

the

tape

end

during

playback

or

record,

the

tape

is

automatically

re-

wound

to

the

beginning

and

the

deck

enters

the

PLAY

or

STOP

mode

by

switching

the

MEMORY

switch

(SW55)}.

KD-A66A/B/C/E/J/U

If

the

tape

counter

displays

“999”

halfway,

since

the

deck

also

enters

the

PLAY

or

STOP

mode,

the

data

in

the

tape

can

be

repeatedly

reproduced

between

“‘0°’

and

‘‘999’’.

To

describe

this

operation,

the

MEMORY

switch

(SW55)

is

set

in

the

PLAY

mode.

AT

first,

when

an

auto-stop

signal

is

emitted

from

the

microcomputer

at

the

tape

end

during

playback,

transistor

XKO6

goes

on,

thus

lowering

the

voltage

at

the

auto

termina!

(pin

5)

of

mechanism

contro!

1C51.

At

this

time,

the

auto-

rewind

instruction

is

emitted

from

1C51.

When

the

tape

is

rewound

to

the

beginning

by

this

instruction,

the

auto-stop

instruction

is

emitted

from

12

of

the

microcomputer.

Likewise,

when

the

volt-

age

at

the

AUTO

terminal

(pin

5)

of

I1C51

is

lowered,

the

PLAY

instruction

is

automatically

emitted

from

the

microcomputer.

Next,

to

describe

this

operation,

the

MEMORY

switch

is

set

in

the

STOP

mode,

At

first,

when

an

auto-stop

signal

is

emitted

from

the

microcomputer

at

the

tape

end

during

playback,

transistor

XKO6

goes

on,

thus

lowering

the

voltage

at

the

said

AUTO

terminal.

At

this

time,

the

auto-rewind

instruction

is

emitted

from

1051.

When

the

tape

is

rewound

to

the

beginning

by

this

instruction,

the

auto-stop

instruction

is

emitted

from

12

of

the

microcomputer.

However,

since

the

base

voltage

of

tansistor

X63

is

kept

to

about

1V

during

the

REW

instruciton,

the

emitter

voltage

of

transistor

X63

is

lowered

to

0.2V

when

transistor

XKO6

goes

on.

At

the

same

time,

transistor

X63

goes

on

and

functions

to

pull

the

STOP

terminal

(pin

1)

of

1C51,

thus

entering

the

deck

into

the

STOP

mode.

In

addition,

with

the

MEMORY

switch

in

the

OFF

state,

the

auto-stop

signal

from

the

microcomputer,

when

transistor

XKO6

goes

on,

passes

across

diode

D63

and

also

functions

to

pull

the

STOP

terminal

(pin

1)

of

1C51,

thus

entering

the

deck

into

the

STOP

mode.

Since

the

MEMORY

STOP/PLAY

function

can

be

per-

formed

even

during

the

auto-rewind

operation

by

the

auto-rewind

circuit,

the

data

in

the

tape

can

be

re-

peatedly

reproduced

between

‘999”

in

the

tape

counter

and

the

tape

end.

XKO6

4

[_

VMwis37-001v

|

STOP]

R38

No.

4193

KD-A66A/B/C/E/J/U

Maintenance

To

get

long,

trouble-free

service,

maintenance

is

important.

Do

not

forget

cleaning

and

demagnetizing.

Cleaning

After

Jong

use,

the

heads

and

tape

part

—

capstan,

pinch

roller,

etc.

—

will

become

dirty

with

dust

or

magnetic

parti-

cles.

Dirty

heads

cause

imperfect

erasing

or

high

frequency

drop-off.

A

dirty

capstan

and

pinch

roller

will

cause

un-

stable

tape

speed,

leading

to

increased

wow

and

flutter.

Always

keep

them

clean

by

following

the

procedure

below.

1.

Heads

1)

Push

Eject

button

to

open

the

cassette

holder.

2)

Use

the

head

cleaning

stick-provided

to

wipe

the

sur-

face

where

the

tape

comes

into

contact

with

the

head.

(It

is

effective

to

moisten

the

cotton

with

alcohol.)

2.

Pinch

roller

and

capstan

Do

the

same

method

as

heads.

3.

Cabinet

When

the

cabinet

becomes

dirty,

wipe

it

with

a

soft

cloth

soaked

with

a

neutral

cleaning

solution

of

a

polishing

cloth.

*

Do

not

use

thinner

or

benzine.

Demagnetizing

The

heads

are

made

from

a

material

resistant

to

magnetiza-

tion

but

after

long

use

they

may

become

magnetized.

A

magnet

brought

into

their

vicinity

can

magnetize

the

heads,

causing

excess

noise.

If

noise

seems

to

have

increased,

demagnetize

the

heads

with

a

head

demagnetizer

through

the

following

procedure.

1.

Turn

the

POWER

switch

OFF.

2.

Wrap

the

tip

of

the

demagnetizer

with

vinyl

tape

or

soft

cloth

so

as

not

to

damage

the

head

surface.

Switch

on

the

demagnetizer

and

bring

it

close

to

the

head.

3.

Move

the

tip

of

the

demagnetizer

slowly

first

to

the

left

and

right,

then

up

and

down

in

front

of

the

head.

Gradually

move

it

away

from

the

head

and

switch

it

off

at

a

distance

of

more

than

30

cm

(12”).

4.

The

erase

head

need

not

be

demagnetized.

The

capstan

shaft

and

tape

guide

should

be

demagnetized

in

the

same

way

as

the

record/playback

head.

Do

not

bring

a

magnetized

metallic

object

(a

screw-

driver,

for

example)

near

the

head

as

this

will

increase

noise.

No.

4193

Removal

of

the

Main

Parts

Observe

care

in

handling

the

parts

since

the

parts

are

small

in

size

and

the

distance

between

them

are

short

due

to

a

deck

design

aimed

mainly

at

compactness

and

high

per-

formance.

ENCLOSURE

ASSEMBLY

PARTS

@.

Cassette

door...

.Depress

the

EJECT

button

to

open

the

cassette

door

Slide

off

the

cassette

door

upwards

(about

5

mm)

to

unlock

its

pawls

of

both

sides.

Remove

the

cassette

door

forward.

Eject

button

Fig.

13

@

Topcover......

Remove

4

screws

fastening

the

top

cover.

Control

knobs

(INPUT

LEVEL,

OUTPUT

LEVEL)

and

Lever

Knobs

(ANRS,

TAPE

SELECT)

otalGeiah

©

wl

edn

Bees

Pull

off

them

forward.

Screws

Fig.

14

Lever

knobs

Control

knobs

@

Bottomcover....Remove

5.

screws

fastening

the

bottom

cover.

@

Mecha.

control

switches

assembly

.....

(When

adjusting

or

replacing

REC/PB

heads

or

Erase

head)

Remove

3

screws

positioned

below

the

mecha.

control

switches

(on

the

bottom

of

the

deck)

and

pull

the

control

section

forwards

—

no

need

of

removing

the

front

panel

assembly.

@

Front

plate

assembly

.....

1)

Remove

a

screw

fastening

the

bracket

to

mechanical

assembly.

JVC KD-A66 Manuale utente

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