Jvc Nivico cd-1667 User manual

NivicoO

SERVICE

MANUAL

Fig.

1

MODEL

CD-1667

1667U

STEREO

CASSETTE

TAPE

DECK

Dimensions:

12.0

(H)

x

38

(W)

x

26.5

(D)

cm

(4-3/8"

x

14-15/16”

x

10-7/16")

Weight:

4.6

kg

(10

Ibs)

*

In

this

Service

Manual,

frequency

is

indicated

in

Hz.

*

In

this

tapedeck,

ISO

screws

are

used.

No.

4073

July,

1972

PUTTAR

TARTU

RLUCGLURORAAMAUUMERERRLUCRCGUORLUOMUCCUORALLUULLLOOR

MU

LULU

sd

po

=O

Mam

Ov

AWM

KODA

CSAIL

LUILILERALLLULTLOREEELLUULILLARLLULLLLURRLLUULLCLARLLLLULLECOOEL

LCL

Power

source:

AC

120V,

60Hz

(CD-1667)

AC

100V,

110

~

120V,

200V,

220

~

230V

(50,

60H,

)

(1667U)

Fuse

capacity:

1.8A,

0.8A

Power

consumption:

30W

(CD-1667)

15W

(1667U)

Track

system:

2-channel,

4-track

Cassette:

C-60,

C-90,

C-120

Tape

speed:

4.8cm/sec.

(1-7/8ips)

Recording

system:

AC

bias

95kHz

Erasure

system:

AC

erasure

Recording

time:

60

min.

for

double

pass

(C-60)

Fast

forward

time:

100

sec.

or

less

(C-60)

Rewinding

time:

100

sec.

or

less

(C-60)

Transistors:

20

:

IC:

4

30

~19,000Hz

(Chrome-tape)

0.7mV,

10ka

20mV

(Signal

source

80ka)

80mV,

330ka

0.5V,

5ka

1V,

3.3ka

Diodes:

17

Frequency

response:

Crosstalk:

60dB

or

more

S/N

ratio:

50dB

Total

harmonic

4%

ot

less

distortion

:

rievhuracteriste!

1590uS,

120uS

Input:

Microphone

DIN

input

AUX.

IN

Output:

DIN

LINE

OUT

Headphones

0.5mW/0.12mW,

82

FOOUVT

TTPO

ATTRA

ETT

TEA

TTT

VICTOR

COMPANY

OF

JAPAN,

CTD.

|IIMIIIIIIINNEILIIINONNILIU

NOE

ILI

HUTT

TERNI00

(TU

CCQNDIILUTIROETTHITT

=

CD-1667,

1667U

2.

Features

w

x

Sb

Pe

&

3.

Names

of

Main

Parts

To

remove

the

tape

noise

automatically,

the

ANRS

circuit

is

incorporated.

The

circuit

is

designed

to

operated

on

the

theory

of

the

low-noise

recording

system

employed

in

a

professional

recording

studio.

At

the

end

of

recording,

playback,

fast

forward

or

rewinding,

the

tape

is

automatically

stopped,

and

the

cassette

is

also

ejected

automatically.

A

long-life

chronios

head

is

used.

The

tape

selector

switch

enables

to

use

a

ultra-high-performance

chrome-tape

featuring

an

excellent

high-frequency

linearity

and

superb

frequency

response.

High

performance

amplifier

incorporating

IC

circuit

and

silicon

transistors.

Smooth

turning

electronic

governor

motor

and

top

grade

tape

feed

mechanism

ensuring

high

accuracy.

Large-sized

high-sensitivity

level

meter

Pause

button

Tape

counter

Headphone

volume

selector

switch

Fig.

2

1.

Pause

button

(PAUSE)

12.

Headphone

terminal

(PHONES)

2.

Operating

buttons

13.

Headphone

volume

selector

switch

3.

Record

button

(REC)

14.

Tape

selector

switch

4.

Volume

control

knob

15.

Microphone

terminal

(MIC)

5.

Eject

button

(EJECT)

16.

Record/Playback

connector

(REC/PB)

6.

Cassette

holder

17.

Auxiliary

input

terminal

(AUX

IN)

7.

ANRS

switch

(ANRS)

18.

Line

output

terminal

(LINE

OUT)

8.

Tape

counter

19.

Input

level

adjuster

(INPUT

ADJ.)

9.

Reset

button

20.

ANRS

indicator

10.

Level

meter

21.

Head

cover

11.

Power

switch

(POWER)

22.

Voltage

Select

switch

(1667U)

CD-1667,

1667U

236

4.

Removal

and

Replacement

of

Main

Parts

Before

Removal:

®

To

remove

the

top

panel,

the

cassette

holder

cover

must

be

removed

first.

Without

removing

it,

the

top

panel

can

not

be

removed.

®

To

remove

the

cassette

holder

cover,

pull

it

in

the

direction

of

the

arrow

shown

in

Fig.

4.

@

The

cassette

deck

is

built

with

many

smail

parts

which

are

densely

installed.

It

should

be

handled

with

special

care.

1.

Construction

and

Disassembly

This

unit

consists

of

the

top

panel

@

,

body

(2)

including

the

mechanism

and

amplifier,

and

cabinet

@.

To

disassembly,

the

unit

should

be

placed

upside

down

to

avoid

scratching

it.

The

cabinet

can

be

removed

by

loosening

the

six

screws.

To

separate

the

body

from

the

top

panel,

remove

the

six

screws

(blue)

indicated

by

arrows

in

Fig.

5.

2.

Electrical

Circuits

2—1.

Removing

the

amplifier

circuit

board

To

remove

the

amplifier

circuit

board,

remove

the

three

screws

((1),

(2)

and

(3))

indicated

by

arrows

in

Fig.

6.

In

this

stage,

the

record

change

mechanism

rod

and

lever

are

connected,

but

the

amplifier

circuit

board

can

be

turned

up

90

degrees.

Next,

remove

the

nut,

and

disconnect

the

rod

from

the

lever.

The

amplifier

circuit

board

can

be

removed

freely.

2—2.

Removing

the

ANRS

circuit

board

Remove

the

four

screws

((4),6),

©

and

()

indicated

by

arrows

in

Fig.6,

and

remove

the

ANRS

circuit

board.

2—3.

Removing

the

oscillation

circuit

board

Remove

the

ANRS

circuit

board

first

accoring

to

2—2

above,

and

remove

the

two

screws

holding

the

oscillation

circuit

board

case.

The

case

now

can

be

removed.

Next,

remove

the

screw

securing

the

circuit

board

to

the

case,

and

the

circuit

board

can

be

removed.

2—4.

Removing

the

RPM

detector

circuit

board

Remove

the

screws

((8)

and

Q))

shown

in

Fig.

6.

The

bracket

is

fitted

with

transistors

for

better

radiation

efficiency.

It

is

not

advisable

to

remove

the

print

circuit

board

and

bracket.

=

Fig.

3

Fig.

4

CD-1667,

1667U

2—5.

Removing

the

power

source

circuit

board

Remove

the

screws

(

and

(i)

)

indicated

in

Fig.

6,

and

the

power

source

circuit

can

be

removed.

2—6.

Replacing

the

fuses

Fuses

are

installed

in

the

positions

(

(2

and

(3

)

in

Fig.

6.

According

to

2—1

and

2—5

above,

remove

the

print

circuit

board.

The

fuse

capacity

is

0.8

A

for

(2

and

1.8

A

for

3

.

Before

replacing

a

fuse,

be

sure

to

check

the

cause

of

fuse

burning.

3.

Mechanism

Parts

@)

08

8

B®

O®

4)

8)

WE)

9d)

@

Fig.

7

3-1.

Removing

the

Motor

(Figs.

8

and

9)

1)

Desolder

the

motor

wires

(red

and

black)

2)

Remove

the

two

screws

(@))

and

62

)

holding

the

motor

@

to

the

motor

bracket.

The

motor

can

be

removed.

3—2.

Removing

the

Flywheel

(Figs.

7

and

8)

1)

Remove

the

screws

(

@3)

and

@4

)

securing

the

lever

@)

locking

the

casette

holder

@).

Then

remove

the

screws

(@5

and

),

and

the

flywheel

holder

()

can

be

removed.

2)

Remove

the

“E”’

ring,

and

pull

out

the

take-up

idler

arm

(6).

3)

Remove

the

capstan

belt

@,

and

pull

out

the

flywheel

@).

The

flywheel

now

can

be

removed.

3—3.

Removing

the

Plunger

(Figs.

7

and

8)

1)

Remove

the

screw

@7

and

nut

securing

the

plunger

(9)

and

slide

bar

together.

2)

Remove

the

two

screws

(

69)

and

)

securing

the

plunger

to

the

bracket

()),

and

the

plunger

can

be

removed.

CD-1667,

1667U

aA

3—4.

Replacing

the

Capstan

Belt

(Figs.

7

and

8)

The

capstan

belt

can

be

replaced

without

removing

the

flywheel

holder

G).

1)

Loosen

the

two

screws

(65)

and

@6

)

securing

the

flywheel

holder

according

to

2—1)

above.

2)

Remove

the

capstan

belt

7)

from

the

motor

@

and

take-up

idler

arm

©),

and

pull

out

the

belt

through

the

space

between

the

flywheel

and

the

flywheel

holder

(6).

3—5.

Removing

the

Cassette

Holder

(Fig.

7)

1)

Loosen

the

four

screws

(4)

,@,@®

and

@)

holding

the

bracket

4)

to

the

chassis

q)

.

2)

Remove

the

spring

pushing

the

cassette

holder

(3)

upward.

3)

Turn

the

bracket

@)

to

the

right,

and

the

cassette

holder

(3)

can

be

removed.

3—6.

Removing

the

Pinch

Roller

(Fig.

9)

1)

Remove

the

“E”

ring

@)

holding

the

pinch

roller

arm

ass’y

(5),

and

the

pinch

roller

ass’y

can

be

removed.

(The

pinch

roller

can

be

removed

from

the

pinch

roller

ass’y

(5)

.)

3—7.

Removing

the

Counter

Belt

(Fig.

10)

1)

Remove

the

amplifier

circuit

board

according

to

2.—2—1

above.

2)

Remove

the

two

screws

(4)

and

46

)

holding

the

bracket

,

and

remove

the

bracket

with

the

relay

circuit

board.

3)

Remove

the

counter

belt

from

the

pulley

(1?

on

the

counter

drive

side.

Note:

After

installing

the

bracket

,

make

sure

that

the

plate

turns

without

contacting

the

lamp

bracket.

For

details,

refer

to

““Auto-Eject”’.

3—8.

Removing

the

Counter

(Figs.

9

and

10)

1)

After

removing

the

counter

belt

,

remove

the

screws

(47)

and

@)

holding

the

counter

bracket

,

and

remove

the

counter

together

with

the

bracket.

2)

Remove

the

two

screws

securing

the

counter

to

the

counter

bracket,

and

remove

the

counter.

Fig.

10

CD-1667,

1667U

5.

Replacement

and

Adjustment

of

the

Heads

If

either

of

the

record/playback

head

and

the

erase

head

shows

low

performance

because

of

wear,

broken

wire

or

excessive

magnetization,

it

should

be

replaced.

1.

Replacing

the

Head

Remove

the

top

cover,

and

the

heads

will

be

exposed

to

view

as

shown

in

Fig.

11.

The

record/playback

head

can

be

removed

by

loosening

the

screws

(3)

and

(4),

while

the

erase

head

by

loosening

the

screws

@

and

@).

After

replacement,

adjust

the

head

for

azimuth.

If

necessary,

adjust

the

level

meter

for

needle

deflection

according

to

6—1

below.

2.

Azimuth

Adjustment

Insert

the

cord

plug

into

the

LINE

OUT

jack

(or

REC/PB),

and

connect

the

other

end

of

the

cord

to

a

vacuum

valve

voltmenter.

Then

play

the

azimuth

adjustment

standard

tape

(e.g.,

JVC’s

VIT-615

10

kHz),

and

turn

the

adjustment

screw

@)

so

that

the

output

will

become

maximum.

If

the

azimuth

adjustment

standard

tape

is

not

available,

play

a

music

cassette.

When

treble

response

becomes

optimum,

set

the

adjustment

screw.

After

this

adjustment,

the

screw

(2)

should

be

locked

with

a

bond.

6.

Main

Adjustments

6—1.

Adjusting

the

Needle

Deflection

of

the

Level

Meters

Both

right

and

left

level

meters

are

so

adjusted

that

the

needles

swing

properly.

But

if

any

of

the

meter

parts

is

repalced,

the

meter

may

require

adjustment

because

of

a

slight

difference

between

the

old

and

new

parts.

If

adjustment

is

needed,

take

the

following

steps.

Recording:

1.

Slide

the

volume

control

knobs

for

both

right

and

left

channels

so

that

the

volume

will

be

at

maximum.

2.

Apply

a

signal

to

the

microphone

jack,

and

check

Fig.

12

to

see

if

the

meter

needles

deflect.

3.

If

both

meter

needles

will

not

swing

evenly,

adjust

the

semi-fixed

resistors

((3)

and

@)

alternately

so

that

both

needles

deflect

evenly

(See

Fig.

12).

Turning

the

resistor

in

the

direction

of

the

arrow

makes

the

needle

swing

far.

For

precise

adjust-

ment,

it

is

advisable

to

connnect

a

100

22

resistor

across

the

head,

and

adjust

the

semi-fixed

resistors

CD-1667,

1667U

=

@)

and

(4)

so

that

the

meter

needle

will

stay

at

O

VU

when

the

voltage

across

the

100

Q

resistor

is

4.5

mV

at

1

kHz.

(For

this

adjustment,

the

bias

current

must

be

cut

off.)

Playback:

1.

After

making

sure

that

the

meter

needles

swing

during

the

recording

operation,

adjust

the

volume

control

knobs

so

that

the

needles

stay

at

0

VU.

Then

start

recording.

2.

Next,

play

back

the

recorded

portion,

and

make

sure

that

the

meter

needles

swing

in

the

0

VU

zone.

3.

If

both

meter

needles

will

not

deflect

evenly,

turn

the

semi-fixed

resistors

(@

and

@))

in

Fig.

12

alternately

to

set

the

needles

to

0

VU.

Turning

the

resistor

in

the

direction

of

the

arrow

makes

the

needle

swing

far.

6—2.

Input

Level

Adjustment

The

DIN

(REC/PB)

input

level

is

adjusted

to

20

mV

(signal

source

impedance

82

kQ),

but

when

the

output

of

the

amplifier

is

excessively

large,

distortion

may

take

place

before

the

volume

control.

In

this

case,

the

following

steps

should

be

taken

for

adjustment.

1.

Place

the

stereo

set

or

the

amplifier

in

the

recording

posisition.

2.

If

the

level

meter

needle

swings

beyond

0

VU

with

the

volume

control

set

at

“3”

or

less,

adjust

the

adjustment

volume

as

shown

in

Fig.

13

so

that

the

meter

needle

will

not

swing

beyond

0

VU

with

the

volume

control

set

at

“5

~

8”.

The

AUX

IN

jack

input

can

be

adjusted

in

the

same

manner.

6—3.

Recording

Bias

Current

Adjustment

The

recording

bias

current

is

adjusted

properly,

and

therefore,

no

adjustment

is

required

normally.

If

the

head

or

other

parts

are

replaced,

adjustment

should

be

made

in

the

following

manner.

1.

Checking

the

bias

current

Place

this

unit

in

the

recording

position,

and

measure

the

AC

voltage

by

V.T.V.M

across

each

head

without

applying

recording

input

through

the

microphone

or

others.

If

the

voltage

measured

is

roughly

as

specified

below,

the

bias

current

is

considered

to

be

normal.

Record

head.......

12

V

(normal

tape),

18

V

(chrome

tape)

Erase

head

........

27V

For

this

test,

be

sure

to

use

a

vacuum

tube

voltmeter

which

is

superior

in

high

frequency

characteristics.

2.

Adjusting

the

bias

current

As

shown

in

Fig.

14,

the

oscillation

circuit

adjuster

is

built

in

the

shield

case,

and

adjustment

can

be

made

by

turning

the

semi-fixed

volume

control.

According

to

the

tape

selector

switch

position,

it

is

necessary

to

make

adjustment

separately

for

the

normal

and

chrome

tapes.

On

the

normal

tape

posisition

(right),

turning

the

semi-fixed

volume

in

the

direction

of

the

arrow

increases

the

current.

On

the

chrome

tape

position

(left),

turning

it

in

the

direction

of

the

arrow

also

increases

the

current.

Magnetic

head

Note:

Bias

current

is

properly

measured

as

follows:

V.T.V.M

Bias

current

Normal

:

490uA

Chrome

:

660uA

Fig.

13

—7-

CD-1667,

1667U

6—4.

Mechanism

Adjustment

1.

Pinch

roller

pressure

(Fig.

15)

Standard

pressure:

350

~

450

g

If

the

pressure

is

not

as

specified,

adjustment

should

be

made

by

replacing

the

spring

or

by

changing

the

spring

position.

2.

Take-up

torque

(Figs.

15

and

16)

Standard

torque:

40

~

70

gr.cm

If

not

as

specified,

1)

Replace

the

take-up

idler

arm

(6).

2)

Replace

the

take-up

idler

arm

pressure

spring.

3)

Clean

or

replace

the

take-up

belt

@.

4)

Clean

the

right-side

reel

rubber

outer

surface,

or

replace

the

reel

rubber.

3.

Fast

forward

torque

(Fig.

15)

Standard

torque:

75

gr.cm

or

more

If

not

as

specified,

1)

Clean

theright-side

reel

rubber

outer

surface,

or

replace

the

reel

disc

ass’y

@1)

.

2)

Clean

the

fast

forward

tire

and

idler,

or

replace

the

fast

forward

idler

ass’y

@2.

3)

Clean

the

flywheel

outer

surface

and

belt.

4.

Rewinding

torque

(Fig.

15)

Standard

torque:

75

gr.cm

or

more

If

not

as

specified,

1)

Clean

the

left-side

reel

rubber

outer

surface,

or

replace

the

reel

disc

ass’y

@3).

2)

Clean

the

rewind

tire

@4.

3)

Clean

the

flywheel

outer

surface

and

belt.

7.

Auto-Ejector

7—1.

Theory

of

Detecting

the

Stop

of

Tape

As

illustrated

in

Fig.

17,

the

turning

force

of

the

disc

on

the

take-up

side

is

carried

to

the

counter,

by

which

the

toothed

plate

integrated

with

the

counter

pulley

is

turned.

The

plate

is

provided

with

the

CdS

detector

element

on

the

upper

side

and

the

lamp

on

the

lower

side.

As

the

plate

turns,

the

CdS

detector

element

radiation

is

shut

by

the

teeth

of

the

rotating

plate.

Thus

the

radiation

goes

on

and

off

quickly

and

transmits

an

AC

signal

to

the

subsequent

circuit

as

a

detecting

signal.

CD-1667,

1667U

8a

Counter

belt

Gear

plate

CdS

element

7—2.

Theory

of

Control

Circuit

Operation

This

circuit

consists

of

three

transistors

and

two

diodes

as

illustrated

in

Fig.

18.

The

AC

signal

from

the

CdS

detector

element

is

amplified

by

X2,

and

rectified

through

Ds

and

De,

then

being

charged

to

Ciz.

As

C12

is

charged,

it

causes

the

base

voltage

of

Xs

to

increase,

and

asa

result,

X3

becomes

conductive,

but

Ri1

(resistor)

causes

the

voltage

to

drop.

Because

of

this

voltage

drop,

the

base

voltage

also

goes

down,

and

Xa

cuts

off

the

flow

of

current.

Accordingly,

no

current

flows

through

the

plunger

(solenoid)

connected

in

series

to

the

collector.

Next,

when

no

signal

is

transmitted,

Ci2

is

not

charged,

and

the

base

voltage

of

X3

drops,

making

X3

non-conductive.

As

a

result,

there

will

be

no

voltage

drop

resulting

from

R11,

and

the

base

voltage

of

X4

rises.

This

makes

X4

conductive

and

allowing

the

current

to

flow

to

the

solenoid.

8

¢

e

=

&

7—3.

Operation

of

Mechanism

I

|

| i

|

i}

|

| |

|

| |

|

L.

As

the

plunger

moves

up

and

down,

it

causes

the

slide

X2

2SC536(F,E)

X3

2SC536(F)

X4

2SC932(E)

bar

to

move.

This

slide

bar

movement

releases

the

operating

buttons

from

the

locked

position

and

also

unlocks

the

cassette

holder.

As

the

cassette

holder

is

a

|

t—|

H4

unlocked,

the

operating

buttons

are

held

stopped

by

eee

eed

poli

sane

SBOE

their

respective

springs,

and

the

cassette

holder

is

turned

up.

Fig.

18

7—4.

Symptoms

causes

by

operation

theory

of

this

mechanism

@

The

cassette

is

ejected

quicker

at

the

end

of

fast

forward

operation

(or

rewinding)

than

at

the

end

of

playback

(or

recording).

This

is

caused

by

the

difference

in

the

level

of

the

AC

signal

from

the

CdS

detector element.

@

With

the

pause

button

depressed,

it

is

possible

to

fast

forward

and

rewind

the

tape,

but

the

control

circuit

is

not

in

action.

Therefore,

the

cassette

is

not

ejected

at

the

end

of

rewinding.

Be

sure

to

release

the

pause

button

before

the

fast

forsard

or

rewinding

operation.

(If

the

cassette

is

not

ejected

at

the

end

of

the

tape,

the

machine

will

be

damaged.)

@

Avoid

depressing

the

playback,

rewind

or

fast

forward

button

before

turning

on

the

power

switch.

Otherwise,

when

the

power

switch

is

turned

on,

the

cassette

may

be

suddenly

ejected,

thus

damaging

the

machine.

7—5.

Check-ups

and

Adjustments

1.

Incase

of

disassembly

or

repair

If

the

disc,

which

is

integrated

with

the

counter

pulley,

keeps

stopping,

the

cassette

is

ejected.

It

is

required

to

check

whether

the

toothed

plate

contacts

the

lamp,

CdS

detector

element

or

the

bracket,

becuase

the

lamp

is

positioned

very

close

to

the

CdS

detector

element.

Also

check

the

counter

for

smooth

rotation

after

disassembly

or

repairs.

Since

the

CdS

detector

element

tends

to

collect

dust,

clean

it

whenever

repairs

or

adjustments

are

made.

2.

Checking

circuits

for

operation

When

the

rewinding

operation

approaches

the

end,

the

ejection

of

the

cassette

tends

to

occur.

For

this

reason,

it

is

necessary

to

check

the

control

circuits

for

operation.

3.

Mechanism

section

If

the

load

on

the

mechanism

section

is

larger

than

the

attraction

of

the

plunger,

the

auto-ejection

will

not

take

place.

In

this

case,

check

the

following

points:

9

CD-1667,

1667U

1)

Check

to

see

if

the

slide

bar

returns

to

its

home

position

smoothly.

Also

check

it

for

bends.

2)

Check

the

operating

button

cam

locks

and

moving

parts

for

molibudenium

grease.

3)

Check

the

plunger

position.

If

it

is

found

shifted

to

the

rear,

adjust

it

correctly.

4)

Check

whether

the

lock

lever

@1)

of

the

cassette

holder

(3)

is

too

tight

or

not.

If

too

tight,

replace

the

cassette

holder

@3)

and

lock

lever

@i)

.

Loe

10

Fig.

19

8.

Noise

Reduction

System

What

is

the

ANRS

circuit

?

ANRS

stands

for

‘“‘“Automatic

Noise

Reduction

System’”’.

Noise

takes

many

forms,

that

is,

noise

produced

in

playback

system,

bias

noise

added

in

recording

process,

and

bulk

noise

peculiar

to

the

tape.

The

ANRS

circuit

is

designed

to

reduce

these

noises

without

impairing

the

frequency

characteristics

unlike

a

conventional

high-pass

filter.

Theory

of

the

ANRS

circuit

In

the

ANRS

circuit,

when

the

recording

signal

level

is

high

(that

is,

the

recording

level

is

at

0

VU),

the

recording

ANRS

circuit

frequency

characteristics

show

rather

flat

curves

(See

Fig.

20).

But

if

the

signal

level

is

lower,

the

recording

is

made

by

stressing

the

intermediate

and

high

range

of

frequency

characteristics.

That

is,

when

the

recording

level

is

lower,

the

intermediate

and

high

ranges

are

compressed.

In

this

case,

the

bias

noise

is

also

recorded,

irrespective

of

the

recording

characteristics.

Accordingly,

the

signal/noise

ratio

is

improved

in

proportion

to

the

degree

of

compression.

To

be

more

precise,

when

the

recording

level

is

40

dB

lower

than

the

standard

level,

improvement

of

the

signal/noise

ratio

is

10

dB

at

5

~

10

kHz.

But

if

the

tape

so

recorded

is

played

back,

the

low

level

signal

is

stressed

at

the

intermediate

and

high

range.

Therefore,

in

the

ANRS

playback

system,

the

characteristics

opposite

to

those

in

the

recording

system

is

given

to

reduce

the

frequency

characteristics

of

the

low

level

signal

at

the

intermediate

and

high

range

(See

Fig.

21).

That

is,

the

intermediate

and

high

range

is

expanded.

In

this

way,

the

bulk

noise

on

the

tape

and

transistor

noise

on

the

playback

amplifier

are

both

reduced,

and

at

the

same

time,

the

playback

signal

level

is

reduced

to

the

original

signal

level.

That

is,

without

impairing

the

original

signal,

the

noise

is

reduced

as

shown

in

Fig.

22.

CD-1667,

1667U

103

40

100

200

400

600

1K

2K

4K

6K

8K

10K

20K

40

100

~200

400600

1K

2K

4K 6K

8K

10K

20K

Fig.

20

Characteristic

graph

of

noise

level

Fig.

2)

a

g

___=

Noise

level

nN

°o

50

100

500

1k

2k

5k

10k

20k

——=_

Frequency

(Hz)

Fig.

22

Function

of

Each

Block

Refer

to

the

block

diagram.

Buffer

Amplifier

This

is

the

emitter

follower

(2SC1335).

It

is

designed

to

reduce

the

influence

to

the

first

half

stage

of

the

system,

and

at

the

same

time,

make

the

filter

circuit

(consisting

of

the

ANRS

control

circuit

and

non-linear

control

elements)

operate

correctly.

Non-Linear

Control

Elements

and

ANRS

Control

Circuit

As

non-linear

control

elements,

transistors

X302

and

X402,

as

well

as

2SC1335,

are

used.

Asa

DC

VBE

is

applied

to

the

circuit

between

the

transistors

B

and

E,

the

impedance

ZcE

between

C

and

E

is

varied

by

the

impressed

voltage

VBE

from

©

up

10

Q.

This

theory

is

also

applied

to

the

AGC

circuit.

The

high-pass

filter

is

made

up

of

the

ANRS

control

circuit

and

the

said

variable

impedance

elements

(Fig.

23).

This

high-pass

filter

has

such

frequency

characteristics

that

they

vary

according

to

the

value

of

the

impressed

voltage

VBE,

as

indicated

in

Fig.

24.

Note

that

the

high-pass

filter

has

a

loss

of

about

25

dB.

During

the

recording

operation,

a

signal

passes

through

this

circuit,

by

which

the

intermediate

and

high

frequencies

are

amplified.

During

the

playback

operation,

the

high-pass

filter

is

inserted

in

the

feedback

loop

of

NF,

and

as

a

result,

it

serves

as

a

low-pass

filter

having

the

reversed

frequency

characteristics.

Control

Amplifier

The

control

amplifier

is

a

circuit

to

generate

the

VBE

which

is

impressed

to

the

transistors,

that

is,

non-linear

control

elements.

In

this

circuit,

the

signal

voltage

is

amplified

by

IC

(IC302

and

402),

and

a

DC

control

voltage

is

produced

by

the

voltage

doubler

rectification

of

diodes,

D301,

302, 401,

and

402.

This

DC

control

voltage

is

varied

by

semi-fixed

volume

controls,

R315

and

415.

The

rectifier

circuit

has

constant

circuits,

C316,

416,

R317

and

417

so

that

the

control

voltage

has

a

proper

transient

characteristic.

In

addition,

bias

traps,

L301,

401,

C317

and

417,

are

provided

to

keep

the

ANRS

circuit

free

from

adverse

effects

caused

by

bias

leaks.

As

part

of

the

control

amplifier,

it

has

a

circuit,

from

which

a

DC

bias

is

applied

to

transistors

of

variable

impedance

elements.

This

bias

current

can

be

varied

by

semi-fixed

resistors,

R320

and

420.

If

Zce

is

too

great,

the

output

of

the

high-pass

filter

exceeds

10

dB,

and

therefore,

by

adjusting

the

bias

current,

the

output

is

kept

at

10

dB.

—11—-

CD-1667,

1667U

Adjusting

the

ANRS

Circuit

Measuring

instruments

required

for

adjustment:

Audio

oscillator

(OSC),

attenuator

(ATT),

high-sensitivity

vacuum

tube

voltmeter,

and

oscilloscope.

Connection:

Remove

the

wires

of

input

side

of

the

ANRS,

and

connect

wires

as

illustrated

in

Fig. 25.

Adjustment:

hs

4.

Repeat

the

adjustment

in

2.

above.

NN

Disconnect

the

red

lead

wire

from

the

power

source

of

the

bias

oscillation

circuit.

Turn

on

the

ANRS

switch,

and

push

the

record

button.

.

Apply

a

frequency

of

5

kHz

—70

dB

to

the

input

of

the

ANRS

circuit

and

adjust

the

semi-fixed

resistor,

R320

(R420)

so

that

the

output

of

the

ANRS

circuit

is

—60

dB.

—45

dB.

ANRS

control

circuit

are

Non-linear

control

element

IZce

.

Apply

5

kHz

—70

dB

to

the

same

input

so

that

the

output

of

the

semi-fixed

resistor

R315

(R415)

is

.

Make

sure

that

there

is

no

deformation

in

the

wave

form.

.

Connect

the

lead

(which

is

removed

in

1.

above)

as

it

was.

Vbe

=

large

Response

Vbe

=

small

Variation

of

Vbe

(db)

100

IK

10K

Frequency

(Hz)

Fig.

24

CD-1667,

1667U

Fig.

25

a

° °

o o

9.

Connection

Diagram

,

8

e

«

eI

5

e468

&

°

.

sou

4

5

vs

1.

Amplifier

Circuit

Board

sag

eis

3

&

Tape

Select

Circuit

Board

Oud

CACY

®

m

n

The

numerals

in

circles

O

in

the

diagram

are

color

codes

of

lead

wires.

@ud

|

7

ae

Recording

lamp

@)

6

UU

WOW

EU

UU

F

a)

l

een

Lug

plate

AM

B®

Ca

D®

ig

©

®

E

5

g

:

=

>

3

oO

ic

a

3

ES

[o}

Ry

Fig.

26

=13

=

a

4

we

ame,

<9

=

©

Volume

®

&

CD-1667,

1667U

2.

ANRS

Circuit

Board

r

+

8

.

A

J

tan

——

foe

|

,~eeomeeel”

|

Ag

\

A

>

a.

(Prous

nl

mo

@

Ox

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j

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2

Le

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uy

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fina

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ny

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wv

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cm

ia

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oy

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——

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jeune

oe

NS

®

ioe

cna

/

nes

qyeaene

os

Soe

&

CD-1667,

1667U

=14—

3.

Input/Output

Circuit

Board

©

Ground

Fig.

28

4.

Power

Source

Circuit

Board

so

2

3s

ue}

2

a6

g

>

¢

3S

4.0

G

F

H

E

im

®@

©

_15—

CD-1667,

1667U

5.

Eject

Circuit

Board

®D

Power

trans,

2

«

Se

,

Motor

=

®D

”

Condenser

Plunger

Instant

switch

CdS

rotation

detecting

element

Motor

switch

Fig.

30

6.

Oscillation

Circuit

Board

o

oO

o

8

§ 8

a

6

‘6.

3s UD

3

$

38

3

=

x

0

ty

8

Power

trans.

2

Condenser

2

Fig.

31

CD-1667,

1667U

—16—

10.

Block

Diagram

Playback

head

Playback

System

Block

Diagram

Playback

NF

equalizer

L-CH

Level

adjust-

a

_{kto3

x104

As

2sc536[_~

|2SC536

Se

Line

amplifier

Headphone

level

change-over

switch

Headphone

trans,

X105

2SC875)

X31}

Buffer

amplifier

Gain

compensator

2SC

|

RI28Z

LD3I41|

ANRS

|

DIO!

control!

unit

|

!

DIN

out

Headphone

LD3150

335

Non-linear

OO)

output

control

(>)

C402

element

O®

2}

@—e"

|

@)

a.

|

D201

x40!

!

L

25C|

|

R228

2

as

cea

eats

ate

ee

6

Line

out

:

©

4p

|X203

X204

X205

=

O

2SC536

7

2SC536)

2SC875)

=

Fig.

32

Recording

System

Block

Diagram

L-CH

Playback

NF

equalizer

NF

Ch

ANRS

Sw.

aed

ee

a

Input

Mic,

Recordin

Headphone

eadphone

leve

adjustment

input

volume

“OFF

1

|

Normal

trans,

change-over

switch

me

2SC536

2SC875

S

Auxiliary

Recording

head

input

:

;

R-CH

Q)

ANRS

ANRS_

:

a

Chrome

circuit

control

circuit

Gain

compensator

w-

4

=

ani

R128

oH

Chrome

/

.

Normal

1335

“s

;

Bane

LOS141

piggy

fs8e1

amplifier

D301~304

|

X302

|

ae

1

Erase

head

Headphone

Non-linear

Control

|

output

control

element

amplifier

I

X

402

IC402

|

@)

2SC133

LD3150

!

= |

D401~404

;

D201

|

R1283

X203

X204

X205

Oo

|2SC536

2SC536

2SC875)

$202

-

Fig.

33

—17-

CD-1667,

1667U

11..

Trouble

Shooting

Electrical

Circuit

1.

Playback

tone

quality

is

poor.

1)

Check

the

record/playback

head

for

dust.

2)

Check

the

record/playback

head

for

wear.

If

worn

excessively,

the

loss

of

treble

response

will

result.

3)

Check

wiring

for

a

short-circuit.

Check

each

transistor

for

condition.

(Check

voltage

according

to

the

circuit

board

parts

diagram.)

4)

Check

the

noise

reducing

circuit

for

condition.

(This

check-up

should

be

made

by

turning

on

and

off

the

switch

of

the

ANRS.)

2.

Recording

tone

quality

is

poor.

The

playback

tone

quality

of

a

recorded

tape

such

as

the

audition

tape

is

good,

but

the

recording

by

this

unit

produces

poor

tone

quality.

In

this

case,

the

unit

should

be

checked

in

the

following

manner.

1)

By

monitoring

a

music

while

recording,

check

the

tone

quality.

2)

If

found

poor,

check

the

wiring

of

the

recording

system

for

a

broken

wire

and

short-circuit.

Check

transistors

for

function

by

measuring

voltage.

3)

If

no

irregularity

is

found,

check

the

recording

bias

current

according

to

6—3

above.

Also

check

the

oscillation

circuit.

4)

Check

the

noise

reducing

circuit

for

operation.

3.

For

other

failures,

check

the

unit

in

the

same

manner

as

other

amplifiers.

Mechanism

Section

As

for

the

torque

and

pressure

of

rollers,

details

are

given

in

“Mechanism

Adjustment”

on

page

00,

and

therefore,

this

section

refers

to

the

adjustement

of

wow

and

flutter.

Adjustments:

If

wow

and

flutter

increase,

check

the

following

points.

If

there

is

a

defect

in

revolving

parts,

the

wow

and

flutter

generated

will

increase

in

propotion

to

the

number

of

revolutions.

Play

a

3000

Hz

standard

tape,

and

the

defective

part

can

be

detected

from

the

sound.

Capstans

Pinch

rollers

Capstan

shaft

has

excessive

run-out.

Flywheel

turns

heavily

(Shaft

seisure,

thrust

play,

etc)

Rough

rotation

(Deformation,

scratches,

or

dust)

Angle

is

incorrect.

Pressure

is

incorrect.

Replace

flywheel.

Adjust

flywheel

holder.

Replace

pinch

roller.

Clean.

Adjust

so

that

it is

parallel

to

capstan.

Adjust

spring.

Take-up

belt

Belt

has

undue

run-out.

Belt

is

dirty

or

slipery.

Replace

take-up

belt.

Clean

or

replace.

Back

tension

Motor

_|

Back

tension

is

irregular,

or

back

tension

is

too

strong.

Replace

supply

disc.

Replace

back

tension

spring

(under

supply

disc),

or

apply

silicon

grease.

Motor

shaft

has

undue

run-out.

Motor

pulley

is

oily

and

dusty.

Take-up

idler

arm

CD-1667,

1667U

Replace

motor.

Clean

motor

pulley.

Pulley

has

deflection.

Pulley

is

stuck.

_—18—

Replace

take-up

idler

arm.

12.

Cleaning

and

Oiling

1.

Cleaning

Clean

the

contact

surfaces

of

the

record/playback

head,

capstan

and

pinch

roller

with

the

tape.

If

the

head

is

dirty,

tone

quality

will

be

greatly

impaired,

or

erasure

will

be

imperfect.

Clean

them

with

a

cloth

moistened

with

alcohol,

benzine,

or

trichloroethylene.

Keep

the

cabinet

free

from

these

chemicals,

or

the

surface

will

be

dissolved.

2.

Oiling

Feed

one

or

two

drops

of

D.T-E.

oil

or

machine

oil

to

the

rewind

roller

shaft

and

pinch

roller

shaft

once

or

twice

a

year

under

normal

conditions

of

use.

Avoid

oiling

them

excessively,

or

rotation

may

become

irregular

because

of

oil

splashes.

—19-

CD-1667,

1667U

13.

Appearnace

Parts

209

AANRS|,

Fig.

35

CD-1667,

1667U

20

—

JVC NIVICO CD-1667 User manual

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