Brother International MD-817 Service Manual - Page 50

Brother International MD-817 Manual

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ITEM PROBLEM #8 Needle (lower) doesn't stop. #9 Needle (lower) stops at different places. CHECK PROBABLE CAUSE REMEDY • Is the synchronizer OK? (NO) (YES) Synchronizer installation position is not suitable. Synchronizer malfunction. Control printed-circuit board malfunction. Position adjustment: 0.5mm Replace the synchronizer. Replace the control box. • Is the V-belt loose? (YES) • Is there oil, grease, dirt scratches, etc. on the syn- chronizer's reflecting sur- face? (YES) (NO) • Is the motor's braking noise loud? (YES) (NO) Insufficient V-belt tension. Dirt of the synchronizer's reflecting surface. Malfunction of the synchronizer. Malfunction of the control printed-circuit board. Reduced motor braking force. Malfunction of the synchronizer. Malfunction of the control printed-circuit board. Adjust the V-belt tension. Clean the reflecting surface. Replace the synchronizer. Replace the control box. Replace the motor brake clearance. Replace the synchronizer. Replace the control box. #10 Poor position of • Is adjustment at syn- needle stop. chronizer possible? (YES) Poor position of needle Adjust needle (lower) stop (lower) stop. between 18 - 22mm. (NO) Reduced motor braking Replace the motor. force. #11 After treadle return, • Is thread trimming speed machine won't oper- suitable? (NO) Low speed is too fast. Adjust VR TRIM (LOW). ate at low speed. (YES) Malfunction of control Replace the control box. printed-circuit board. #12 Thread trimmer • Is the 1-pin plug (of the 12 doesn't function. pins) in the control box connected? (NO) Improper connection of the Connect the 1-pin plug cor- 1-pin plug. rectly. • Switch OFF the power and measure the resistance of the thread trimmer sole- noid. Is there about 7ohms be- tween 0 and 0 of the 12 pins? (NO) Malfunction of the thread Replace the thread trimmer trimmer solenoid. solenoid. • Does the 8A fuse (at the top of the control printed- circuit board) appear nor- mal? (NO) 8A fuse failure. Replace the 8A fuse. #13 Needle (upper) • Is the speed at low speed doesn't stop. OK? (NO) Low speed is too fast. Adjust VR TRIM (LOW). • Is the synchronizer OK? (NO) Improper installation of the Replace the synchronizer. synchronizer. (YES) Malfunction of the control Replace the control box. printed-circuit board. - 46 -

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ITEM
PROBLEM
CHECK
PROBABLE
CAUSE
REMEDY
#8
Needle
(lower)
doesn't
stop.
•
Is
the
synchronizer
OK?
(NO)
(YES)
Synchronizer
installation
po-
sition
is
not
suitable.
Synchronizer
malfunction.
Control
printed
-circuit
board
malfunction.
Position
adjustment:
0.5mm
Replace
the
synchronizer.
Replace
the
control
box.
#9
Needle
(lower)
stops
at
different
places.
•
Is
the
V
-belt
loose?
(YES)
•
Is
there
oil,
grease,
dirt
scratches,
etc.
on
the
syn-
chronizer's
reflecting
sur-
face?
(YES)
(NO)
•
Is
the
motor's
braking
noise
loud?
(YES)
(NO)
Insufficient
V
-belt
tension.
Dirt
of
the
synchronizer's
re-
flecting
surface.
Malfunction
of
the
syn-
chronizer.
Malfunction
of
the
control
printed
-circuit
board.
Reduced
motor
braking
force.
Malfunction
of
the
syn-
chronizer.
Malfunction
of
the
control
printed
-circuit
board.
Adjust
the
V
-belt
tension.
Clean
the
reflecting
surface.
Replace
the
synchronizer.
Replace
the
control
box.
Replace
the
motor
brake
clearance.
Replace
the
synchronizer.
Replace
the
control
box.
#10
Poor
position
of
needle
stop.
•
Is
adjustment
at
syn-
chronizer
possible?
(YES)
(NO)
Poor
position
of
needle
(lower)
stop.
Reduced
motor
braking
force.
Adjust
needle
(lower)
stop
between
18
—
22mm.
Replace
the
motor.
#11
After
treadle
return,
machine
won't
oper-
ate
at
low
speed.
•
Is
thread
trimming
speed
suitable?
(NO)
(YES)
Low
speed
is
too
fast.
Malfunction
of
control
printed
-circuit
board.
Adjust
VR
TRIM
(LOW).
Replace
the
control
box.
#12
Thread
trimmer
doesn't
function.
•
Is
the
1
-pin
plug
(of
the
12
pins)
in
the
control
box
connected?
(NO)
•
Switch
OFF
the
power
and
measure
the
resistance
of
the
thread
trimmer
sole-
noid.
Is
there
about
7ohms
be-
tween
0
and
0
of
the
12
pins?
(NO)
•
Does
the
8A
fuse
(at
the
top
of
the
control
printed
-
circuit
board)
appear
nor-
mal?
(NO)
Improper
connection
of
the
1-pin
plug.
Malfunction
of
the
thread
trimmer
solenoid.
8A
fuse
failure.
Connect
the
1
-pin
plug
cor-
rectly.
Replace
the
thread
trimmer
solenoid.
Replace
the
8A
fuse.
#13
Needle
(upper)
doesn't
stop.
•
Is
the
speed
at
low
speed
OK?
(NO)
•
Is
the
synchronizer
OK?
(NO)
(YES)
Low
speed
is
too
fast.
Improper
installation
of
the
synchronizer.
Malfunction
of
the
control
printed
-circuit
board.
Adjust
VR
TRIM
(LOW).
Replace
the
synchronizer.
Replace
the
control
box.
-
46
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