Technics RS-646DS-D User manual

“ORDER

NO.

ARD-7706063C

Service

Manual

Cassette

Deck

RS-646DS-D

Portable

High-Fidelity

Stereo

Cassette

Deck

with

Separate

Bias/Equalizer

and

Mic

Attenuator

RS-640U

MECHANISM

SERIES

Specifications

(Catalog

specifications

for

sales)

Power

requirement:

AC;

110/220V,

50/60

Input:

MIC;

sensitivity

0.25

mV/applicable

microphone

Power

consumption;

impedance

400Q~

10K

DC;

12V,

eight

R-20

size

dry

cell

batteries

INE;

sensitivity

mV/input

impedance

Motor:

1-DC

electronical

speed

control

motor

DIN;

sensitivity

mV/input

impedance

2.7

Track

system:

4-track

2-channel

stereo

recording

and

playback

Output:

LINE;

output

level

420

mV/load

impedance

Tape

speed:

4.8cm/s

over

Battery

life:

Approx.

hours

with

alkaline

batteries

DIN;

output

level

420

mV/output

impedance

Wow

and

flutter:

0.1%

(WRMS),

£0.2%

(DIN)

HEADPHONE

;

output

level

mV/load

Frequency

response:

CrOz

tape;

50~14,000Hz

+3dB

impedance

14,000

(DIN)

Monitor

speaker;

output

power

0.8

(monaural)

Normal

tape;

50~14,000Hz

+3dB

Head:

2-head

system

~14,000Hz

(DIN)

1-super

permalloy

head

for

record/playback

Signal-to-noise

ratio:

Dalby

in;

66dB

(above

5kHz)

1-doub!

gap

ferrite

head

for

erasure

Dolby

out;

56 dB

Dimentions:

36.3cm(W)

10.6

cm(H)

28.0

cm(D)

(signal

level

max.

recording

level)

Weight:

5.0kg

(without

batteries)

Fast

forward

and

rewind

time:

Approx.

130

seconds

with

C-60

cassette

tape

Specifications

are

subject

chang

without

notice.

gees

Matsushita

Electric

Trading

Co.,

Ltd.

Technics

P.O.

Box

288,

Central

Osaka

Japan

LOCATION

CONTROLS

AND

COMPONENTS

DOAO@®D@OOOO@QOY

Eject

button

Record

button

Rewind

button

Fast

forward

button

Playback

button

Stop

button

@®

Cassette

compartment

cover

Pause

button

Silent-stop

button

Tape

counter

and

reset

button

Level

meter

Level/battery

check

meter

Built-in

speaker

Handle

Level

controls

lock

button

Meter

light

button

Battery-check

button

nput

level

controls

Tape-end

indicator

Tone

contro!

Speaker

volume

control

Equalization

selector

Bias

selector

Dolby

noise-reduction

switch

Limiter

switch

Input

selector

Microphone

jacks

Headphones

jack

Voltage

selector

switch

Car

battery

input

jack

connection

socket

Line

output

jacks

Record/playback

DIN

socket

Line

input

jacks

SSSSSSSSSSSOSHSSSSsdQaGesoso@

32) 33)

Fig.

DISASSEMBLY

INSTRUCTIONS

—

(B)

Fig.

—

Procedure

remove

—

Pes.

Shown

fig.

——.

Top

panel

(A),

(B),

(C),

(D),

4,2,2,2,3,4

2,3,4

Brent

natal

(G),

(H)

3,9

2,3

Mechaniern

(1)

neinlifier

MEASUREMENT

ADJUSTMENT

BEFORE

ADJUSTMENTS

REPAIRS

---.--

For

electrically

adjustments

only,

each

the

variable

resistors

and

connection

points

for

adjustment

can

seen

when

the

bottom

cover

removed

shown

fig.

below.

Make

adjustments

referring

each

adjustment

description.

—Connection

: :

;

woes

point

for

pele

ope

Connection

point

<B)

for

L-ch

playback

level

meter

adjustment.

frequency

response

adjustment.

When

electrical

parts

printed

circuit

board

are

repaired,

rernove

the

mechanism,

amplifier

and

power

supply

printed

circuit

board

from

the

case

shown

fig.

below.

When

each

section

reconnected

connectors,

the

operation

each

section

can

confirmed.

Note:

Secure

the

mechanism

assembly

the

jack

angle.

Secure

the

power

supply

printed

circuit

board,

the

same

way,

the

headphone

jack

angle.

ADJUSTMENTS

Before

measuring

and

adjusting

“Overall

frequency

response”,

“Overall

distortion”

and

“Overall

S/N

ratio”.

confirm

that

the

characteris-

tics

items

below

are

within

standard

which

have

much

relation

influence

electrical

performances

above.

Head

azimuth

adjustment.

Bias

current.

Playback

gain.

Overall

gain.

Playback

frequency

response.

TEST

INSTRUMENTS

Prepare

test

instruments

which

are

equivalent

accuracy

those

shown

below.

The

test

instruments

should

inspected

and

corrected

specialists

once

every

months,

because

long

period

use

without

maintenance

may

increase

errors

indication.

Warm-up

the

test

instruments

for

minutes

and

the

set

measured

for

minutes

before

taking

the

measurements.

not,

there

may

arise

error

difference

between

the

initial

value

and

the

stabilized

value

measured

after

“aging”

Specifications

test

instruments.

(1)

Audio

frequency

oscillator

Oscillation

frequency:

5Hz~

500

kHz

ranges)

Frequency

tolerance:

+(3%

+1Hz)

Sine

wave

Output

voltage

(at

25°C):

5Vrms

£10%

(without

load)

2.5Vrms

+10%

(with

6002

load)

Output

frequency

response:

Within

£0.2

dB,

20Hz~20kHz

Within

£0.5dB,

5Hz~

500

kHz

Distortion

factor:

Not

than

0.05%,

200

20kHz

Not

than

0.5%,

5Hz~

500

kHz

Output

impedance:

6002

unbalanced,

within

15%

Output

attenuator:

OdB,

20dB,

error;

within

+0.2dB

Temperature

use

set:

Temperature

= 0 ~

40°C,

humidity

90%

less

(2)

Automatic-stop

distortion

meter

(with

vacuum

tube

voltmeter)

Distortion

factor

measurement

Frequency

(fundamental

wave):

400Hz,

1kHz

+10%

Measurement:

0.1~

100%

ranges)

Input:

50mV~50V

Fundamental

wave

attenuation:

Level

measurement

Measurement:

(—60

dB)

(30

dB)

ranges)

Frequency

response

(1kHz

basis):

20Hz~100kHz

£0.3¢dB

Input

impedance:

1MQ2

+10%,

less

than

Error

indicated

value:

Within

£3%

1kHz

Output

terminal

Frequency

response:

OQHz~100kHz

+1dB

100kH2~1MHz

+3dB

Output

voltage:

1Vrms

10%

(1kHz

sine

wave)

(3)

Attenuator

Input

impedance:

6002

unbalanced

Maximum

attenuation:

121dB

Minimum

attenuation:

0.1dB

(4)

Oscilloscope

Cathode

ray

tube:

Effective

ranges

88cm

Vertical

axis

Input

sensitivity

30mV~30V/cm

Frequency

band:

~2MHz

Transient

time:

180ns.

Input

impedance:

1MQ,

Horizontal

axis

Tuning

range:

MHz

Sweep

time:

lus~

100ms/cm

External

Sweep:

1Vp-p/cm

(5)

Digital

electronic

counter

Number

figure:

(decimal

system)

Input

sensitivity;

100mVrms

Input

impedance:

1MQ,

Frequency

measurement

range:

10Hz~

100

kHz

Counting

time:

0.1s,

Is,

10s

(6)

Wow

meter

Measured

center

frequency

range:

3kHz

+4%

Input

level

range:

30mV~3V

Input

impedance:

About

unbalanced

Measurement:

0.01~3%

ranges)

Indicator

error:

Maximum

error

indicated

value

+5%

each

range.

Frequency

response:

Contorming

weighting

curve

characteristics

(WRMS),

JIS

C5551.

Flat

characteristics

(RMS)

0.5~200Hz,

within

(4Hz

basis)

Meter

indication

system:

Effective

value

indication,

conforming

JIS

C5551.

Meter

response

characteristic:

About

sec.

Oscillation

frequency:

frequencies

(3kHz,

3kHz

+3%)

Temperature

range:

0~40°C

MEASUREMENT

CONDITIONS

Standard

measurement

conditions

Ambient

temperature:

10~30°C

(50~86°F)

Ambient

humidity:

~90%

Power

voltage

accuracy:

Position

tape

recorder

When

measuring,

place

the

unit

under

test

horizontal

position.

Oscillator

output

voltage

adjustment

Connect

the

equipments

shown

the

following

and

adjust

the

oscillator

output

control

knob

for

(f=1kHz)

through

the

attenuator

while

keeping

the

attenuator

dB.

When

supplying

signal

the

tape

recorder

amplifier,

adjust

the

input

level

using

the

attenuator.

Output

control

knob

Audio

frequency

oscillator

}

Attenuator

Vacuum

tbe

voltmeter

Oscilloscope

f=1kHz

Testers

Output

voltage

(OdB)

Il.

TEST

TAPE

Test

tape

life

The

frequently

the

test

tape

used,

the

tape

characteristics

will

deteriorate

(e.g.

lowering

recorded

level,

worsening

frequency

response

particularly

high-frequency

range,

and

increase

wow

due

tape

elongation)

until

measured

values

be-

come

unreliable.

Even

such

case

when

tape

not

used,

but

stored,

for

long

period

time,

tape

shows

deterioration

per-

formance

because

self

damagenetization

due

storage

conditions,

etc.

Please

refer

the

tape

life

specitication

and

use

care

not

use

tape

longer

than

its

rated

life

when

servicing.

Frequence

use:

Not

than

times

for

each

tape

length.

Storage

period:

Not

than

months.

Test

tape

PARTS

NO.

PARTS

NAME

SPECIFICATIONS

REMARKS

Standard

recording

level

times

repetitive

recording

and

frequency

response

Tape

speed:

1-7/8ips.

(4.8cm/s)

tape

Full

track

(10

min.)

OdB:

STANDARD

REC.

LEVEL

(160pWb/mm)

1-7/8ips.

(4.

Wow

and

tape

speed

tepe

Tape

Speed:

1-7/8os,

(t.Bom/s

OdB:

250pWb/mm

Tape

speed:

1-7/8ips.

(4.8cm/s)

Azimuth

tape

6.3kHz

Full

track

(15

min)

OdB:

250pWb/mm

Reference

blank

tape

(Normal)

Unrecorded

tape

(20

min.)

Reference

blank

tape

(CrO2)

Unrecorded

tape

(20

min.)

iV.

MEASUREMENT

ADJUSTMENT

METHOD

NOTE:

Make

sure

capstan

and

pressure

roller

are

clean.

Judgeable

room

temperature:

20-+5°C

(68+9°F)

Make

sure

heads

are

clean.

Bias

selector:

Low

Pressure

pressure

roller

Equipment:

Tension

gauge

(max.

500

gr)

Dolby

switch:

OUT

Output

level

control:

MAX

MEASUREMENT

ADJUSTMENT

Place

UNIT

into

playback

mode.

Hook

the

tension

gauge

pressure

roller

lever

and

pull

the

direc-

tion

the

arrow

shown

fig.

Measure

the

tension

the

moment

when

the

pressure

roller

moves

away

from

the

capstan.

Standard

value:

390+60

Adjustment

method

Bend

the

part

(A)

the

pressure

roller

spring

either

direction

shown

the

arrow

until

the

correct

pressure

attained.

Equalizer

selector:

120.8

REMARKS

Playback

mode

Pressure

roller

spring

Fig.

Takeup

tension

Equipment:

Cassette

torque

meter

(SRK-CT

RP8063)

Mount

cassette

torque

meter

UNIT.

Place

UNIT

into

playback

mode

and

read

takeup

torque.

Measure

several

times

and

determine

the

mean

value.

Standard

value:

55+15gr-cm

the

measured

value

not

within

standard,

firstly

clean

the

rotational

parts

the

mechanism

with

alcohol,

and

still

not

within

standard,

make

the

following

adjustment.

Adjustment

method

Adjust

turning

the

plate

spring

attached

the

takeup

reel

table

(See

fig.

10).

Playback

mode

Plate

spring

Fig.

Head

azimuth

adjustment

Equipment:

VTVM

Oscilloscope

Test

tape

(azimuth)

---

C-AA

Record/playback

head

adjustment

Test

equipment

connection

shown

below.

VTVM

Fig.

Test

tape

Playback

mode

Oscilloscope

Play

azimuth

tape

(C-AA,

6.3

kHz).

Adjust

record/playback

head

angle

adjustment

screw

(8)

fig.

that

output

level

LINE

OUT

becomes

maximum.

Measure

both

channels,

and

adjust

levels

for

equal

output.

After

adjustment

lock

head

adjustment

screw

with

lacquer.

Playback

mode

R/P

Head

Tape

speed

Equipment:

Digital

electronic

counter

frequency

counter

(RP8067)

Test

tape---

C-WAT

MEASUREMENT

ADJUSTMENT

Tape

speed

accuracy

Test

equipment

connection

shown

below.

LINE

OUT

Test

tape

Playback

mode

Digital

electric

counter

Fig.

Play

test

tape

(C-WAT

3,000Hz),

and

supply

playback

signal

fre-

quency

counter.

Measure

this

frequency.

the

basis

3,000Hz,

determine

value

following

formula:

f—3,000

3.000

100

(%)

where,

f=measured

value

Take

measurement

middle

section

tape.

Tape

speed

accuracy

Standard

value:

+1.5%

Adjustment

method

Play

the

test

tape

(middle).

Adjust

the

tape

speed

adjustment

shown

page

that

fre

quency

becomes

3,000

Hz.

Tape

speed

fluctuation

Make

measurements

same

manner

above

(beginning,

middle

and

end

tape),

and

determine

difference

between

maximum

and

minimum

values

and

calculate

follows:

fi—fe

Tape

speed

fluctuation

3.000

100

(%)

fi1=maximum

value

f2=minimum

value

Standard

value:

1.5%

REMARKS

Playback

mode

Wow

and

flutter

Equipment:

Wow

meter

Test

tape

---

C-WAT

Test

equipment

connection

shown

below.

LINE

OUT

Test

tape

Playback

mode

Wow

meter

Fig.

Use

wow

test

tape

(3,000Hz)

and

measure

its

playback

signal

wow

meter.

Wow

and

flutter

expressed

percentage

and

that

measurement

can

weighted

JIS

network

(WRMS).

Measure

middie

section

test

tape.

Standard

value:

0.10%

(WRMS)

Playback

mode

Playback

frequency

response

Equipment:

VTVM

Oscilloscope

Test

tape

---

C-FH

Playback

gain

Equipment:

*VTVM

Oscilloscope

Test

tape---

C-FH

MEASUREMENT

ADJUSTMENT

Test

equipment

connection

same

“Head

azimuth

adjustment”

but

use

the

test

tape

(C-FH)

instead

head

azimuth

tape

(See

fig.

11).

Place

UNIT

into

playback

mode.

Play

frequency

response

test

tape

(C-FH).

Measure

output

level

1OkHz,

8kHz,

4kHz,

1kHz,

125Hz

and

63Hz

and

compare

output

level

with

standard

frequency

333Hz,

LINE

OUT.

Make

measurement

for

both

channels.

Make

sure

that

the

measured

value

within

the

range

specified

the

frequency

response

chart.

Playback

frequency

response

chart

150Hz

250Hz

333H2

sobez

ski

Fig.

measured

value

not

within

standard,

adjust

the

following

points:

Change

the

“Connection

points’

the

amplifier

pattern,

and

then

adjust

the

playback

frequency

response.

@lf

the

high

range

(8~10kHz)

decreases

about

—1~

—1.5aB,

short

circuit

connection

points

(@)

shown

fig.

@lf

the

high

range

(8~10kHz)

decreases

about

—1.5~

—2qB,

also

short

circuit

connection

points

(B)

shown

fig.

Test

equipment

connection

shown

fig.

11.

Play

standard

recording

level

portion

test

tape

(C-FH

333Hz),

and

using

VTVM

measure

the

output

level

LINE

OUT

jack.

Make

measurement

for

both

channels.

Standard

value:

0.42V

(—7dB)

Adjustment

method

measured

value

not

standard,

adjust

VR1

(L-CH),

VR2

(R-CH)

(See

fig.

page

17).

After

adjustment,

check

“Playback

frequency

response”

again.

REMARKS

Playback

mode

;

Playback

mode

Playback

S/N

ratio

Equipment:

VTVM

Oscilloscope

Test

tape---C-FH

Empty

cassette

Test

equipment

connection

shown

fig.

11.

put

level

VTVM.

Refer

"Playback

gain

adjustment”.

Place

empty

cassette

(which

has

been

cut)

and

play

again.

Measure

noise

level

this

time

using

VTVM,

and

determine

ratio

this

level

test

tape

output

signal

voltage

(333

Hz).

Standard

value:

Greater

than

43dB

example

calculation

shown

below.

Es=playback

output

signal

voltage

test

tape

(333

Hz)

En=playback

output

noise

level

Es=0.42V

(—7dB)

En=0.003

(—50dB)

S/N

ratio=

_0.42V

—

140

0.003

log::

140=43dB

S/N

ratio

Es(dB)

—

En(dB)

—7

—(—50)

43dB

Playback

mode

Play

standard

recording

level

test

tape

(C-FH

333Hz)

and

read

out-

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