Harman Kardon AX20 Owners Manual - Page 12

Hum

Adjustment:

One

HUM

ADJUST

-HIGH

LEVEL

control

and

one

HUM

ADJUST

-LOW

LEVEL

control

are

located

on

the

right

side

of

the

chassis

in

front

of

the

electro-

lytic.

Each

operates

simultaneously

to

adjust

both

left

and

right

channels.

To

ad-

just

for

minimum

hum,

set

the

FUNCTION

switch

to

TUNER,

turn

the

tuner

off

(if

connected)

and

turn

the

LOUDNESS

control

full

on.

Adjust

the

HIGH

LEVEL.

hum

control

for

minimum

hum.

Now

set

the

FUNCTION

switch

to

the

TAPE

-LO

position,

and

set

the

LOW

LEVEL

hum

control

for

minimum

hum.

System

Hum

or

Noise:

In

any

high

fi

delity

installation,

hum

may

be

caused

by

the

interconnection

of

a

record

changer,

tuner

and

amplifier,

as

a

result

of

the

cables

and

different

grounds.

A

good

way

to

eliminate

this

problem

is

to

fi

rst

disconnect

everything

but

the

speakers

from

the

amplifier,

and

listen

for

hum.

If

the

hum

persists,

make

the

hum

and

balance

adjustments

described

above.

Try

reversing

the

ampli-

fi

er

power

plug.

Now

plug

in

the

record

player.

If

hum

appears,

try

reversing

the

record

player

power

plug,

and

try

connecting

a

wire

from

the

record

player

chassis

to

the

amplifier

chassis.

In

this

way,

connect

the

tuner,

tape

deck

and

other

devices

in

turn.

Note

that

hum

may

be

picked

up

by

defective

interconnecting

cables,

and

by

interconnecting

cables

running

too

close

to

power

cables.

MAINTENANCE

AND

REPAIRS

Fuse:

In

the

event

of

a

potentially

damaging

failure

of

tubes

or

components,

the

Model

AX20

is

protected

by

a

M

ampere,

type

3AG

fuse,

located

on

the

rear

of

the

unit.

If

this

fuse

is

blown,

it

should

be

replaced

only

with

one

of

the

same

rating.

Replacing

with

a

fuse

of

higher

rating

will

not

protect

the

amplifier,

arid

may

result

in

severe

damage,

which

will

not

be

covered

by

the

factory

warranty.

Routine

Maintenance

Due

to

the

conservative

design

and

high

quality

components

of

the

Model

AX20,

no

routine

maintenance

other

than

yearly

tube

checking

is

advised.

Oc-

casional

resetting

of

the

hum

and

output

balance

adjustments,

following

the

procedure

described

above,

will

keep

the

unit

operating

at

peak

efficiency.

These

adjustments

should

certainly

be

made

after

any

tube

replacement.

Repair:

Only

the

most

qualified

service

technician should

be

employed,

as

special

equipment

and

training

is

required

to

properly

service

a

high

fi

delity

amplifier.

This

manual

contains

information

of

great

value

to

the

repairman,

and

should

be

kept

available.

Factory

Warranty

Stations

are

maintained

in

most

major

cities.

For

the

ad-

dress

of

the

nearest

one,

or

for

any

other

information

relating

to

your

Harman-

Kardon

products,

write

to

the

attention

of

the

Customer

Service

Department,

Harman-Kardon,

Inc.,

520

Main

St.,

Westbury,

N.

Y.

Be

sure

to

include the

model

and

serial

number

of

the

set

in

question.

A

short

description

of

your

complete

in-

stallation

is

often

of

help

in

answering

your

questions.

Harman Kardon AX20 Owners Manual - Page 12

Adjustment, System, Noise, MAINTENANCE, REPAIRS, Routine, Maintenance, Repair

Page 12 highlights