JVC M-7050 Manuel utilisateur

JVC

Instruction

Book

Service

Manual

STEREO

POWER

AMPLIFIER

M-7050

SSS

Sea

eae

SIG

WARNING:

PREVENT

FIRE

SHOCK

HAZARD,

NOT

EXPOSE

THIS

APPLIANCE

RAIN

MOISTURE.

For

Customer

Use:

Enter

below

the

Model

No.

and

Serial

No.

which

located

either

the

rear

bottom

the

cabinet.

Retain

this

information

for

future

reference.

Model

No.

Serial

No.

Service

manual

No.

2469

July,

1979

E30580-804A

IMPORTANT

(In

the

United

Kingdom)

Mains

Supply

(AC

240

V~,

only)

IMPORTANT

not

make

any

connection

the

Larger

Terminal

coded

Green.

The

wires

the

mains

lead

are

coloured

accordance

with

following

code:

Blue

(Neutral)

Black

Brown

(Live)

Red

these

colours

not

correspond

with

the

terminal

identifi-

cations

your

plug,

connect

follows:

Blue

wire

terminal

coded

(Neutral)

coloured

Black.

Brown

wire

terminal

coded

(Live)

coloured

Red.

doubt

—

consult

competent

electrician.

Note

recommend

that

you

should

disconnect

the

cord

from

the

outlet.

INTRODUCTION

Thank

you

for

purchasing

the

JVC

M-7050

stereo

Power

Amplifier.

You

are

now

the

owner

truly

sophisti-

cated

system

component

incorporating

many

advanced

features.

“Super-A”

high

efficient

150W

power

output

stage

(is

equal

class

operation)

extra

low

distortion

(is

superior

class

operation),

high

slew

rate

(+300V/ysec),

un-

rnesurerable

TIM

distortion,

non

magnetic

alminium

chassis-

base

eliminate

the

magnetostriction,

and

high

capacitive

power

supply

are

just

few

the

host

features

which

combine

produce

the

best

possible

sound.

JVC

also

manufactures

the

EQ—7070

Stereo

Phono

Equalizer,

matching

preamplifier

and

the

SEA—7070

Stereo

Graphic

Equalizer,

matching

frequency

characteristic

controller

for

use

with

the

M—7050

Power

Amplifier.

Before

you

begin

using,

please

read

the

instructions

carefully

sure

getting

the

best

possible

performance

from

the

new

unit.

Wishing

you

memorably

enjoyable

listening.

WARNING

Dangerous

voltage

inside

CAUTION

(

prevent

electric

shock,

not

remove

screws,

covers

cabinet.

user-serviceable

parts

inside.

Refer

servicing

qualified

service

personnel.

CONTENTS

Instruction

Manual

page

Front.panel.):.:

si.

Important

notes

2...

Troubleshooting...

0.0.0.0...

eee

tee

eee

Block

diagram.

6.2...

eee

Performance

graphs...

2...

Technical

description...

0...

Specification

©...

ees

Precautions

servicing

Adjustment

procedure

the

amplifier

Check

after

servicing

Exploded

views

Parts

list

exploded

views

Location

circuit

boards

Schematic

Diagram

(For

only

qualified

service

personnel)

cto,

et,

Instruction

Manual

FRONT

PANEL

PHONES

POWER

Switch

Headphones

jack

(PHONES)

Exclusively

for

monitoring

purposes.

Employ

this

facility

the

following

cases,

for

example:

locate’the

beginning

particular

section

tape

when

speaker

sound

desirable.

monitor

the

sound

transmitted

remote

place

when

the

amplifier

used

public

address

system.

(Note)

Plugging

the

headphones

does

not

switch

off

the

speaker

sound

automatically.

When

you

wish

listen

sound

from

the

headphones

only,

set

the

SPEAKER

switches

OFF.

POWER

switch

Press

turn

the

power

on.

The

red

indicator

lamp

push

knob

will

light

and

the

POWER

meters

will

illuminated.

turn

the

power

off,

press

the

switch

again

release.

Panel

IImination:

For

period

immediately

after

the

POWER

switch

turned

ON,

the

illumination

the

POWER

meters

red.

Wait

for

about

seconds

until

changes

white.

continues

red

for

longer

span,

the

protection

circuit

operating

for

some

reason.

Turn

the

POWER

switch

OFF

and

check

the

cause

malfunctioning.

——

Power

meter

SPEAKER

Switch

POWER

meters

The

output

power

indicated

wattage

the

compressed

logarithmic

scale

reference

the

8-ohm

load

impedance.

SPEAKER

switches

listen

the

speaker

system

connected

the

rear

panel

SYSTEM-1

terminals,

press

the

SYSTEM-1

switch.

listen

the

speaker

system

connected

the

rear

panel

SYSTEM-2

terminals,

press

the

SYSTEM-2

switch..

Both

speaker

systems

can

heard

pressing

both

switches.

When

SPEAKER

switch

pressed,

the

green

indicator

lamp

the

corresponding

switch

lights.

(Note)

the

load

impedance

lower

than

ohms,

the

protection

circuit

activated,

resulting

inter-

mittent

sound.

single

pair

speakers

driven

time,

the

speaker

impedance

may

between

and

ohms.

two

pairs

speakers

are

driven

simultaneously,

the

speaker

impedance

should

between

and

ohms.

CONNECTION

DIAGRAM

Refer

item

No.

page

Speaker

system

1622

Input

LEVEL

volume

Normally,

set

the

“MAX”

position.

the

preamplifier

produces

excessively

large’’

gain,

turn

the

control

counter-

clockwise

until

the

proper

adjustment

obtained.

Refer

item

No.

page

Refer

item

No.

page

Speaker

system

1692

SEA-7070

Graphic

equalizer

Pre-amplifier

Turn

table

Tape

Deck

IMPORTANT

one,

——

eeen

eoeow

Installation

Select

dry,

level

place

which

neither

too

hot

nor

too

cold

(between

—5°

and

°C/23°F

and

104

°F).

Leave

space

between

the

power

amplifier

and

the

wall

provide

good

ventilation.

not

allow

curtain,

table

cloth,

etc.

block

the

ventilation

holes.

Keep

the

power

amplifier

away

from

direct

sunlight.

not

place

heater.

not

place

locations

subject

vibrations.

not

place

locations

subject

dust.

Keep

far

from

tuner

and

preamplifier

possible

prevent

noise.

Power

cord

not

handle

the

power

cord

with

wet

hands.

not

bend

the

power

cord

double.

When

unplugging

from

the

wall

outlet,

always

pull

the

plug,

not

the

power

cord.

Malfunctions

not

insert

any

metallic

object

inside

the

unit.

not

allow

water

get

inside

the

unit.

not

employ

thinner

benzine

clean

the

cabinet.

First

clean

with

neutral

cleaner

and

then

wipe

with

dry

cloth.

Power

switch

not

plug

the

power

cord

into

outlet

until

all

connections

are

complete.

Switch

the

power

off

when

connecting

other

components

it.

REAR

PANEL

Connecting

with

other

components

may

result

trouble,

such

oscillation

hum.

Connect

ground

terminals

this

set

and

other

components

each

other.

SUBSONIC

and

DIRECT

INPUT

terminals

not

connect

different

kinds

signals

simultaneously

input

terminals.

Input

cannon

connector

(for

professional

use)

(Unbalanced)

AC:

these

terminals

are

employed,

the

input

signal

passes

through

filter

having

cut-off

frequency

and

slope

6dB/oct,

which

results

reduction

ultra-low

frequency

noise,

such

that

encountered

with

warped

records,

and

prevents

speaker

intermodulation

distortion.

The

filter

also

eliminates

the

preamplifier

leak

voltage,

thus

protecting

the

speakers.

DIRECT:

These

input

terminals

are

directly

connected

the

power

amplification

circuit.

Since

the

M-7050

employes

amplifier

circuitry,

there

coupling

capacitor

between

the

input

circuit

and

the

power

amplification

stages.

Protective

circuit

When

the

protective

circuit

has

been

activated,

switch

off

the

power

and

determine

the

cause

follows:

The

speaker

load

impedance

Using

speakers

with

impedance

less

than

ohms

(or

short

circuit

across

the

speaker

terminals)

activates

the

protective

circuit

and

results

intermittent

sound

out-

put.

When

the

speaker

switch

the

“1

and

2”

position,

use

pair

speakers

having

impedance

high-

er,

“1”

“’2”

position,

use

speaker

higher.

Input

overload

The

speaker

produces

intermittent

sounds.

Detecting

the

offset

voltage

The

offset

voltage

more,

activates

the

pro-

tective

circuit

and

results

sound

output.

Caution

indicator

When

the

protective

circuit

has

been

activated,

meter

illumination

changes

red.

TROUBLE

SHOOTING

What

seems

trouble

not

always

real

trouble.

{

Make

sure

first.

[

sound

]

Both

channel

Are

indicators

Yes

Does

the

relay

the

speaker

switch

Yes

functioning?

operate?

set

ON?

One

channel

only

Reverse

the

and

Does

the

relay

Check

for

speaker

connections.

operate

connections

Does

the

channel

with

sound

shift?

Yes

Navsound

Yes

the

input

level

volume

Yes

Check

for

trouble

the

preamplifier

IfOK......

set

maximum?

connected

component.

Both

channels

Does

the

replacement

the

preamplifier

connected

component

correct

distorted

sound?

Distorted

sound

only

Does

the

channel

with

distorted

sound

shift?

defect

the

M—7050

One

channel

Reverse

the

and

connections.

There

may

trouble

the

M—7050

self.

Consult

your

dealer.

BLOCK

DIAGRAM

YBLAW

8Y3MOd

ANddNS

YAMOd

39VLS

YSBAING

dWY

Y3M0d

A1ddNS

YAMOd

3OVLS

LNdLNO

TAA37

(00)

LOaYIa

@-WALSAS

Y3axVadS

(Ho

LINDYID

svia

v-y4adns

(Ov)

SINOSSNS

SANOHd

YOLINOW

Z2HOLIMS

LINDAID

SANILOSLOYd

Yy3ayvV3ads

LINDAID

Ssvig

(Sv)

SINOSSNS

(a4)

(10

(9q)

LOaYIa

T3A37

dWY

Y3aM0d

PERFORMANCE

GRAPHS

THD

vs.

Output

power

;

0.03

{

Distortion

measurement

system

0.02

tae

1KHz

0.0008%

20Hz

0,0011%

{

20KHz

0.0014%

pat

0.01

0.007

0.005

0.003

0.002

_——

KHz

0.001

0.0007

100

200

300

500

Power

output

(W/8

}

Spectrum

harmonic

distortion

(dB)

—70

}

20K

100K

200K

}

20K

100K

200K

kHz

Fundamental

kHz

Fundamental

Measurement

System

Super—A

Characteristics

TIM

distortion

(Low

pass

filter

fe=100

kHz)

(dB}

3.18K

6.36K

9.54K

12.72K

15K

3.18K

6.36K

9.54K

12.72K

15K

19.08K

{He}

15.9K

(He)

15.9K

The

spectrum

input

signal

Output

signal

M-7050

(Same

input

signal)

af.

20K

100K

kHz

Fundamental

class

3.18K

6.36K

9.54K

12,72K

15K

(Hz)

15.9K

example

TIM

distortion

(TIM

distortion

sum

components

less

than

kHz

which

showed

with

arrows.)

O8K

TECHNICAL

DESCRIPTION

Super

power

amplifier

big

problem

has

remained

unsolved

the

progress

regarding

amplifier

technology:

how

can

class-A

operation

made

compatible

with

high

power

efficiency?

The

class-A

operation

best

terms

low

distortion;

its

critical

drawback

such

that

its

power

loss

greater

than

the

available

output

power.

Because

this,

class-B

amplifiers

have

generally

been

applied

for

power

amplification

because

they

offer

both

acceptable

distortion

and

power

efficiency.

However,

long

class-B

amplifiers

are

employed,

the

occurrence

crossover

distor-

tion

and

switching

distortion

inevitable.

Although

the

improvements

circuit

elements

have

realized

fairly

good

class-B

amplifiers,

when

their

values

distortion

are

referred

to,

the

‘‘nature”

distortion

still

detrimental

the

re-

produced

sound

quality.

solve

this

problem

improving

circuit

technology,

JVC

has

developed

its

new

‘’Super-A”’

power

amplifier.

The

Super-A

power

amplifier

consists

voltage

amplifier

stage

whose

distortion

minimized

compensating

for

the

non-linearity

semiconductors,

and

aclass-A

power

amplifier

stage

which

includes

bias

circuit

for

raising

the

power

effi-

ciency

such

degree

comparable

that

class-B

amplifier.

JVC’s

Super-A

power

amplifier

offers

the

following

features:

Power

efficiency

extremely

high

despite

the

class-A

operation,

greatly

reducing

power

loss

and

heat

generation

compared

with

conventional

class-A

amplifiers.

Switching

distortion

inherent

class-B

operation

com-

pletely

eliminated;

perfectly

zero.

AVecE

distortion

*1,

ACob

distortion

and

Vpe

dis-

tortion

“3

are

all

extremely

low

because

the

unique

non-distortion

circuit

configuration.

“1

Distortion

caused

non-linear

variations

current

gain

due

variations

collector-emitter

voltage

VCE.

Distortion

caused

non-linear

variations

amplifier

gain

which

are

caused

non-linear

variations

feedback

capacity

Cob

due

variations

collector-emitter

voltage

VCE.

Distortion

caused

non-linear

variations

base-emitter

voltage

VBE

power

transistor.

Distortion

measurement

system

Distortion

‘“Super—A”

Fig.

Output

and

residual

distortion

waveforms

measur-

ing

instrument

Fig.2

Output

and

distortion

waveforms

Super-A

am-

plifier

Fig.

Output

and

distortion

waveforms

class-AB

ampli-

fier

Voltage

amplifier

stage

utilizing

‘‘Super-A”’

performance

the

utmost

Fig.

shows

operating

characteristics

common-emitter

transistor;

varies

VCE

varies,

resulting

Vce

distortion

described

above.

Fig.

shows

variation

the

feedback

capacity

Cop

re-

lation

VCE.

This

non-linear

variation

Cop

due

varia-

tions

VCE

causes

non-linear

variation

the

amplifier

gain,

leading

the

Cob

distortion

mentioned

above.

Fig.

shows

operating

characteristics

common-base

transistor.

What

noteworthy

about

this

type

operation

that,

though

its

current

gain

dB,

its

output

linearity

constant-

current

drive

fairly

good

since

scarcely

varies

with

varia-

tions

VcE

(a=

shown

the

equal

distance

between

adjacent

base

current

curves.

example

the

cascode-connected

amplifier

circuit

shown

Fig.

The

features

this

circuit

are

good

frequ-

ency

response

(because

mirror

effect

due

Cob)

and

high

output

impedance.

This

means

that

this

circuit

eliminates

distortion

effectively

combining

the

advantages

common-emitter

and

base-emitter

configurations.

The

driver

stage

the

Super-A

power

amplifier

employs

applied

circuit

this

kind

and

drastic

reduction

distoriton

the

result.

Fig.4

Output

characteristics

common-emitter

amplifier

Fig.5

Cop

characteristic

Fig.6

Output

characteristics

common-base

amplifier

Fig.

Cascode

amplifier

Distortion

‘‘class

AB”

f=10

kHz,

THD=0.0008%

Fig.

f=10

kHz,

Output

power=100W/8

QO,

THD=0.0009%

Fig.

f=10

kHz,

Output

power=100W/8

THD=0.0022%

Fig.

IB1

Vee

Fig.

Emitter

Configration

Vcs

Fig.

Base

Configration

SPECIFICATIONS

Circuitry..........

Direct-coupled

circuitry

with

F.E.T.

cascode

connected

double

differential

input

and

parallel-push

pull

output

SUPER-A

Output

power.......

150W

892

Total

harmonic

distortion.........

0.0004%

(1KHz

150W

8&2)

(Mesured

Y.H.P.

HP-1B)

0.003%

(20Hz

20KHz,

150W

822)

0.03%

(20Hz

100KHz,

150W-822)

Inter

moduration

distortion.........

0.003%

(60

Hz:

kHz=

1,8)

Power

bandwidth

....5

100KHz

(0.02%,

892,

IHF)

TIM

(Transient

Intermodulation

distortion)

........

unmeasurable

Fig.

Cob

characteristic

Slew

Rate

........

Switching

distortion.

Hum

Noise......

Frequency

charactor

Subsonic

Filter.....

Input

sensitibity/

impedance.......

Output

..........

Power

suply.......

Power

consumption.

Dimensions

.......

Fig.

Cascode

amplifier

+300V/p

sec.

less

than

200

(Short

circuit)

.DC

100KHz,

+0,

—0.2dB

18Hz

6dB/oct

.1V

(input

level

volume

max)

/47KQ

than

120dB

(1.H.F.A)

200(1KHz)

882

speaker-1

4Q.~

16Q

speaker-2

4Q.~

160

speaker

142

801~

162

Monitor

phone

Refer

page

Refer

page

160

m/m

(H),

425

m/m

(W),

415

m/m

(D)

22.4

(49.3

Ibs)

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