Brother International MD-817 Service Manual - Page 22

Control

box

Control

box

(Model

DB2-B737)

The

high

speed

dial,

backtack

stitch

dial,

power

lamp,

needle

position

switch,

one

-stitch

modification

switch,

starting

slowly

switch

and

connector

for

synchronizer

are

arranged

on

the

front

of

the

control

box.

All

these

parts

are

already

provided

on

the

control

circuit

board.

The

control

circuit

board

is

installed

on

the

inside

of

the

control

box.

The

power

circuit

board

is

at

the

back

and

the

speed

control

unit

is

on

the

left

side

wall.

The

right

side

wall

is

furnished

with

one

15A

fuse

for

the

110

—

240V

single-phase

type,

two

5A

fuses

for the

200

—

240V

three-

phase

type

and

two

3A

fuses

for

380

—

440V

three-phase

type.

The

control

circuit

board

is

provided

with

the

8A

fuse

for

solenoid

load.

*Do

not

fail

to

secure

the

fuse

holder

cap

after

replacing

or

inspecting

the

fuses.

*Never

short-circuit

the

lamp

terminal

(AC

6V

or

12V

terminal)

for

lighting,

or

the

transformer

may

be

damaged.

Control

circuit

board

Explanation

of

each

dial

*Do

not

turn

the

dial

when

not

necessary.

Models

B737

•

B748

•

B791

•

B793

•

B795

•

B798

Each

respective

speed

becomes

higher

when

any

of

VR

C)

to

O

is

turned

clockwise.

1.

TRIM

(LOW)

VR

C)

is

for

thread

trimming

speed.

2.

INCH

VR

T

is

for

inching

speed.

3.

SLOW

VR

C)

is

for

starting

slowly.

4.

EBT

VR

Cl

is

for

backtacking

speed.

5.

AUTO

VR

CO

is

for

automatic

sewing

speed.

6.

SBL

VR

C)

is

for

setting

the

maximum

start

backtacking

speed.

7.

SBT

VR

®

is

for

start

backtacking

speed.

8.

HIGH

VR

C)

is

for

setting

the

maximum

normal

sewing

speed.

9.

VVR

VR

C)

is

for

limiting

overvoltage

and

has

been

factory

-ad-

justed.

Never

adjust

it.

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NOTE:

When

the

machine

is

not

a

twin

-needle

sewing

machine

and

its

thread

trimming

speed

is

the

same

as

its

inching

speed,

the

speed

should

be

adjusted

using

TRIM

(LOW)

VR

C)

with

the

INCH

VR

C)

turned

fully

counterclockwise.

CAUTION:

Other

dials

are

factory

set,

so

that

they

never

require

adjustment.

Note

1:

It

is

dangerous

to

touch

the

dial

because

high

voltage

is

applied.

Do

not

fail

to

turn

off

the

power

switch

before

adjust-

ment.

To

check

the

setting,

turn

it

on

again.

Note

2:

Take

care

that

the

driver

does

not

touch

other

parts

but

the

dial

for

adjustment.

Adjust

the

dial

with

great

care.

They

may

be

broken

if

turned

past

the

stop

point.

Note

3:

When

any

dial

is

turned

by

mistake,

turn

it

back

so

that

the

red

index

marks

match

each

other.

-18-

Brother International MD-817 Service Manual - Page 22

Control, circuit, board

Page 22 highlights