Phase Linear 400 Service Information

Phase Linear 400

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the

meter

will

indicate

slightly

less

than

it

did

on

tests

of

the

good

transistors.

That

is

the

clue

which

determines

the

defective

device

within

its

group

of

six.

Typically,

the

meter

will

indicate

.4

ohms

on

the

good

devices

and

.1

ohm

on

the

defective

one.

Occasionally

it

will

indicate

1

or

2

ohms

on

the

good

ones

and

.6

ohms

or

1.6

ohms

(.4

ohms

less)

on

the

defective

one.

This

requires

reading

the

meter

with

care

to

spot

this

small

differential.

ІЁ

a

high

reading

of

5

ohms

or

more

is

obtained,

suspect

that

the

driver

transistor

is

shorted.

Step

#2.

Using

an

ordinary

pair

of

pliers,

grasp

the

defective

device

by

its

top

hat and

pull

it

out

of

its

socket.

Reverse

the

procedure

to

install

the

replacement.

Step

#3.

After

the

defective

transistors

have

been

replaced,

check

the

driver

transistors

(the

very

bottom

ones

on

each

heat

sink).

If

the

drivers

are

good,

the

chances

are

98%

that

the

amplifier

will

perform

normally

if

the

above

steps

have

been

followed.

If

the

drivers

are

defective,

some

parts

on

the

board

may

have

to

be

replaced.

(See

step

#4).

Step

#4.

To

service

the

board,

proceed

as

follows:

Remove

the

phillips

screws

that

secure

the

top

and

bottom

plates.

Place

the

amplifier

flat

on

its

back,

with

the

front

panel

facing

up.

Remove

the

four

bolts

that

secure

the

front

panel.

Do

not

use

a

wrench

on

the

front

panel

or

scratches

will

occur.

Hold

the

bolts

on

the

front

panel

with

thumb

and

index

finger,

and

remove

the

nut

from

the

back

of

the

panel

with

a

nut

driver

or

wrench.

The

front

panel

will

lift

off

and

fold

over

towards

the

back

of

the

amplifier.

It

will

then

rest

on

the

bench

along

one

edge,

held

by

cable

bundles.

Remove

the

four

nuts

holding

the

circuit

board

and

"fold"

the

board

out,

away

from

the

chassis,

using

its

cable

harnesses

as

hinges.

This

allows

access

to

the

front

and

back

of

the

board.

When

the

board

is in

the

folded

out

position,

it

should

be

rested

on

a

small

support

of

some

kind

to

relieve

tension

on

the

cable

harnesses.

Step

#5.

If

even

one

of

the

devices

is

found

to

be

defective,

you

may

prefer

to

replace

Q4,

05,

06,

07,

Ов,

Рз,

Dg,

D6,

Оу,

Dg,

and

Dg

on

the

circuit

board.

Not

all

of

these

parts

will

be

defective,

but

they

are

inexpensive,

and

it

may

be

easier

to

replace

them

all

than

to

spend

time

checking

and

pondering

which

should

not

be

replaced.

If

04

is

found

to

be

defective,

diodes

D3

and

Dg

will

also

be

defective.

Be

certain

that

the

protection

circuit,

consisting

of

05,

06,

Dg,

and

ру

is

good.

If

the

unit

is

re-

turned

to

the

customer

without

checking

these

devices,

the

amp-

lifier

will

certainly

fail

the

first

time

someone

shorts

the

speaker

leads

together.

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Owner's Manual13 pages

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Phase Linear 400 Specifications

General

Brand	Phase Linear
Model	400
Category	Amplifier
Language	English

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