Brother BAS-370, BAS -375 Service Manual

•• •••• CONTENTS •••••o

DISASSEMBLY AND ASSEMBLY
FOR TRANSPORTING .......... .					1-1
MECHANICAL DESCRIPTIONS ..					1-2
[]Needle bar and thread take-up, lower
shaft, and rotary hook mechanisms •					1-2
[Z]Presser plate mechanism		.....••••••			1-3
[ID Drive, feed mechanism		..•.•••••..•			1-4
!!]Intermittent presser foot mechanism					1-5
[§]Thread trimmer mechanism			••..•..•.		1-6
[§]Auto eject mechanism •••••.•.•..••					1-7
11] Bottom mechanism •.••••.••••.•..					1-8
DISASSEMBLY ................. .					2-1
[]]Covers •••••.•••..••••.•••..•.•					2-1
lZJPresser plate mechanism		••••••••.•.			2-2
~Needle plate mechanism		••••..•.••.			2-2
[!]Rotary hook mechanism		......••••.			2-3
liD Bottom mechanism •.•••••..••.•..					2-3
liDThread trimmer mechanism					. 2-4
11] Intermittent presser foot mechanism					2-5
liD Needle bar and thread take-up
mechanism	................ ...				2-6
				•
ASSEMBLY ..................... .					3-1
[]]Needle bar and thread take-up
mechanism ••.•••••••••••.••.•					3-1
[Z]Intermittent presser foot mechanism					3-2
[IDThread trimmer mechanism			...•.••.		3-3
[!]Bottom mechanism •.••.••..••.••.					3-4
[ID Rotary hook mechanism		•••..••.•..			3-5
liD Needle plate mechanism		••...•..•..			3-6
llJCovers ....•....•..•...•....••.					3-7
STANDARD ADJUSTMENTS . . . .					4-1
[]]Adjusting the needle bar stroke				• • • • .	4-1
~Adjusting the needle bar height				• . • • .	4-1
[IDAdjusting the clearance between the
needle and the rotary hook			. . • • • • •		4-2
[!]Adjusting the presser foot height				• • . •	4-2
i:IDAdjusting the presser foot • • • . • • • • . .					4-2
[§]Adjusting the intermittent presser
foot lift stroke • • • . • • • • • . • . • . . . .					4-3
[l]Adjusting the presser plate height					4-4

!IDAdjusting the presser plate moving speed						4-4
~Adjusting the presser plate pressure ...						4-5
lrn!Adjusting the bottom plunger					••••••	4-5
lll!Adjusting the auto eject mechanism ••						4-6
~Adjusting the thread trimmer				•••••••		4-7
~Adjusting the backlash		••.••••.••••				4-8
IM!Adjusting the belt tension			••••••.•••			4-9
ll§lAdjusting the timing between the
needle and feed mechanism						4-10
li§JAdjusting the home position				•.••.••		4-10
lll]Adjusting the over travel		••.•••••••				4-12
ELECTRICAL EQUIPMENT ...... .						5-1
[]]Fuse ••.••••••.••••.•••.••••.••						5-1
lZJPower supply equipment			••••••••••			5-2
@!Circuit board ••••••.•••••••••••••						5-3
[!]Replacing the circuit board			•••••••••			5-5
liD LEDs of servo motor driver			..•..•.••			5-6
liD Function and position of sensors					.••••	5-7
ll]Connectors explanations		••.•••••••				5-10
[IDSetti ng the DIP switch		•.•.•••.•..				5-12
~Setting the memory switch			•••.••••			5-13
lrnl Using the optional output			•••••••••			5-14
lll1 Diagnosis flowchart	•••.••••••••.					5-15
OPTION ................ ·~· ...... .						6-1
[i]Sub clamp •••.•.•.••.•••••••••••						6-1
[Z]Beam sensor thread breakage detector						6.:.2
[IDNeedle thread presser assembly					•••••	6-4
[!]Two-stage thread tension			••••.•.••.			6-5
liD Intermittent presser foot control						6-6
mechanism ••...•.••••••.•••••
IIDJig pattern sensor	••••••••••••••••					6-8
TROUBLESHOOTING GUIDE . . . .						7-1
ERROR CODE LIST						7-4
CONTROL CIRCUIT
BOARD DIAGRAM						7-5

From the library of: Superior Sewing Machine & Supply LLC

DISASSEMBLY AND ASSEMBLY FOR TRANSPORTING

The sewing machines are 1820 mm wide for BAS-370, 2620 mm wide for BAS-375, and they both are 1415

mm long, and 1363 mm high. The sewing machines are disassembled to make them easy to transport.

Assemble the sewing machines referring to item .. [§] Needle plate mechanism" in ASSEMBLY.

<BAS-370 sewing area: 800x400 mm>

The above figure shows the sewing machine without the needle plate, the rack cover,. the oil pan, and the presser hinge, when the needle plate support bracket is folded.

<BAS-375 sewing area: 1200x400 mm>

The above figure shows the sewing mathine without the needle plate, the rack cover, the oil pan, and the presser hinge, when the needle plate support bracket is folded.

1-1

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MECHANICAL DESCRIPTIONS

II1 Needle bar and thread take-up, lower shaft, and rotary hook mechanisms

1. Needle bar and thread take-up mechanism

1)When the motor 0 rotates in the direction of the arrow, the motion is transmitted to the thread take-up crank@) through the upper shaft@.

2)The needle bar crank e secured to the thread take-up crank @) moves the needle bar clamp @ up and down via the needle bar crank rod 0.

3)The needle bar fl attached to the needle bar clamp @ is guided by needle bar bushes (U) @ and (D) @, and the needle bar guide slide block@, and smoothly moves up and down.

2.Lower shaft and rotary hook mechanism

1)When the motor 0 rotates in the direction of the arrow, the motion is transmitted to timing pulley (U) ID through the upper shaft@.

2)Timing pulley (D) @ secured to the lower shaft @ transmits the motion to the lower shaft @ via the timing belt m.

3)	The spiral gear @ is secured to the tip of the lower shaft @ , and engaged with the pinion aJ attached
	to the rotary hook shaft @. When the lower shaft @ rotates onetime, the rotary hook shaft @ rotates
	two times.
4)	The rotary hook@ secured to the tip of the rotary hook shaft@	rotates similarly.
, <To turn the pulley manually >
	When the pulley® is pressed in the direction of the arrow, the stopper lever @1 is locked, and the pulley
	shaft gear m is engaged with the gear fEJ, the upper shaft	@ can be turned manually. When the

stopp.er lever W is pulled in the direction of the arrow, it is unlocked.

1-2

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~Presser plate mechanism

1)	When the air pressure is supplied to the cylinder	@ from the air tube 0, the presser arm front @)
	secured to the cylinder@ is pushed forward, and the motion is transmitted to link {A) 0.
2)	Link {A) 0 is connected to link (B) 0 via the stud	@),and also connected to the presser arm 6 via the
	clevis pin@. The presser arm 6 is lowered by pivoting the clevis pin@).

3)When the presser arm 6 is lowered, and the clevis pin @,the stud @,and the cylinder support shaft «!) are arranged in a line, the material pressing pressure is at its maximum, and the material is securely held.

4) When the air pressure is supplied to the cylinder@ from the air tube ID, the presser arm 6 rises.

1-3

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@]Drive, feed mechanism

<X direction>

1)	When the AC servo motor 0 rotates, the motion is transmitted to the X-Y timing pulley 9 through the
	gear@ and the X-gear@, and the X-timing belt 0 operates.
2)	The X-timing belt 0 operates the ball spline f) via the X-driving timing pulley@}.
3)	The ball spline 6	operates the rack gear@) via the X-driving gear@.
4)	The rack gear @>	is secured to the X-movable plates ([!),and the X-movable plates ([!) are guided by the

LM guide ill. The rotating motion of the AC servo motor 0 is converted to X-directioli movement.

<Y direction>

r---.-h:

L..

1)When the AC servo motor@ rotates, the X-Y timing pulley@ rotates via the gear@ and theY-gear ID, and theY-timing belt@ operates.

2)TheY-timing belt@ rotates theY-shaft (ID via theY-driving timing pulley 0).

3)When theY-shaft@ rotates, the timing belt@) operates via the Y-R timing pulley@.

4)The timing belt tiD is secured to the belt retention plate fD, which is secured to the X-hold frame 0.

5)The X-hold frame fh is guided by the LM-guide@, and moves in theY direction.

1-4

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II) Intermittent presser foot mechanism

<When the pulley rotates>

1)	When the upper shaft . 0 rotates, the presser lifter cam @ attached to the upper shaft		0 moves
	eccentrically, the intermittent presser connecting rod@ oscillates intermittent feed arm (R) 0.
2)	The oscillation of intermittent feed arm (R) 9 is transmitted to link (L)@) through U-UD feed arm (L) 0.
3)	Link (L)	€) oscillates the intermittent lever @ guided by the intermittent support	& ·and the
	intermittent guide@) .
4)	The oscillation of the intermittent lever@ is transmitted to the presser bar clamp ((i), and the presser bar
	clamp ((i)	moves up and down.

<When the presser foot is raised>

1)	When the valve operates, and the presser bar lifter cylinder (D operates presser bar lifter arm (B) @ in
	the direction of the arrow, the presser bar lifter connecting rod@ is pulled in the direction of the arrow.
2)	The presser bar lifter connecting rod @ operates the presser bar lifter lever ID in the direction of the
	arrow, and raises the ·presserbar clamp ®.
	1-5

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~Thread trimm.er mechanism

1)	When the thread trimming signal is sent, and the valve operates, the thread trimmer cylinder 0
	operates in the direction of the arrow.
2)	The thread trimmer cylinder 0 operates the movable knife holder @) in the direction of the arrow via
	the thread trimmer connecting rod@ .
3)	The movable knife e secured to the movable knife holder @) is engaged with the fixed knife 0 , then

the thread is trimmed.

1-6

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[§]Auto eject mechanism

1)When the cassette plate assembly 0 is attached to the feed mechanism, and either the ejector sensor @ detects the two positionings {A) @),or the presser lifter pedal is depressed, the valve stops operating and

	the ejector cylinder 9 operates in the direction of the arrow.
2)	The motion is transmitted to the cylinder connecting plate 0 and the guide plate @ which are attached
	to the ejector cylinder e.
3)	Because the guide plate ®	is guided by the pin of the pin plate assembly fi, the horizontal movement
	of the ejector cylinder 9	is converted to vertical movement, and the motion is transmitted to the guide
	plate@.
4)	When the guide plate ®	pulls into positioning {A) @),the cassette plate assembly 0 is secured to the
	feed mechanism.
5)	When sewing is completed or the presser lifter pedal is depressed, the valve operates, and the ejector
	cylinder 9 moves in the opposite direction to the arrow. The guide plate ® pushes positionin·g{B) @,
	and the cassette plate assembly 0 comes off the feed mechanism.

1-7

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11] Bottom mechanism

1)	When the valve operates at the start of sewing, the bottom cylinder 0 operates in the direction of the
	arrow.
2)	The bottom lever @ attached to the bottom cylinder 0 transmits the motion to the bottom plunger 0
	via the belt shift bar@.
3)	When the valve stops operating at the end of sewing, the bottom cylinder 0 moves in the opposite
	direction to the arrow, and the bottom plunger 0 returns to its original position.

1-8

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DISASSEMBLY

II] Covers

1) Remove the screws, the front cover 0, the frame side covers@, and the rear cover@). 2) Remove the screws, and tables {A) 0 and (D) 0.

3)Remove the screws, and the table cover®.

4)Remove the nut 6, and the operation box assembly@).

NOTE: The operation box assembly@ is connected to the cord. Be careful when removing it.

5)Remove the screws, and tables {B)@ and {C) «i>.

6)Remove the screws, the belt presser plates Q), and the dust belt@.

7)Remove the screws, the arm motor cover@, the arm rear cover ID, and the arm front cap {G).

8)Remove the screws, the eye guard@, and the face plate 4D.

2-1

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0, and the presser plate

~Presser plate mechanism

1) Remove the four bolts assembly@.

2) Release the air, and remove the cassette plate assembly@ from the auto eject mechanism e.

@1 Needle plate mechanism

1)	Remove the screws, the needle plate left		0 ,
	the needle plate inner @ , and the needle plate
	right@.
2)	Remove the bolt 9,	the four needle plate
	supports €) 1 and two needle plate supports (B)
	@_
	NOTE: For the BAS-375,	remove the bolt	f) 1
	and the needle plate support side@.
3)	Remove the four bolts@.
4)	Loosen the four bolts®.
5)	Fold the needle plate support bracket ID inside
	(in the direction of the arrow).

2-2

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[!]Rotary hook mechanism

1)	Remove the two screws 0, and the needle
	plate@.
2)	Remove the screw @), and the rotary hook
	bobbin case holderS.
3)	Loosen the three screws 0, and the rotary hook

@.

~ Bottorrt mechanism

Be sure to release the air.

1) Remove the stop rings 0, and the link pin@.

2)	Remove the stop ring@), the washers 0 and 0,
	and the bottom lever 0.
3)	Remove the two air tubes G.
4)	Remove the stop ring @,the washer @, and
	the bottom cylinder®.

2-3

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[§]Thread trimmer mechanism

Be sure to release the air.

1)Remove the two screws 0, and the needle plate@.

2)Remove the two screws@), and the movable knife 0.

3)Remove the two bolts@, and the fixed knife presser@.

4)Remove the screw f), and the fixed knife@.

5)Remove the screw@, and the lower thread finger 4ll>.

6)Remove the bolt ID, the stud screw@, and the thread trimmer connecting rod@.

7)Remove the stop ring ID, and the movable knife holder@.

8)Remove the two air tubes@ .

9)Remove the set screw Q), the support lever shaft@, and the thread trimmer cylinder assembly @.

2-4

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[Z]Intermittent presser foot mechanism

1)Remove the three screws 0 I and the face pi ate @.

2)Remove the adjust screw@) 1 the spring guide 0 1 the spring 0 I and the washer@.

3)Remove the screw f) 1 and the presser foot@.

4)Loosen the screw €> 1 and remove the presser bar 4ID by pulling it downward.

5)Remove the two bolts mI the intermittent guide@ I and the U-U D feed lifter lever roller@.

6)Remove the stop ring ffi.

7)Loosen the set screw@ I and remove the set collar(@.

8)Remove the intermittent support assembly {f}.

9)Remove the stud screw@.

10)Remove the roller shaft@ I and the intermittent lever fli> along with link {L) fD .

11)Remove the presser bar clamp 0.

2-5

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(I] Needle bar and thread take-up mechanism

1) Remove the three screws 0, and the face plate@.

2} Remove the set screw@, the needle e, and the needle bar thread guide 0.

3)Remove the oil cap@.

4)Loosen the screw f), and remove the needle bar@ from the arm by lifting it upward.

5}	Remove the screw (left-hand screw} @,and the needle bar crank rod ®		along with the needle bar clamp
	Q). Be sure not to drop the needle bearing@ and the needle bar guide slide block@.
	NOTE: The needle bearing@ is not used for the thick material specification.
6)	Remove the oil cap ffi.
7)	Loosen the two set screws	@, and remove the needle bar crank ®.	Be sure not to drop the needle
	bearing @ and the washer@.
8)	Loosen the set screw ®,and	remove the thread take-up support shaft W, and the thread take-up f1).

2-6

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ASSEMBLY

[I] Needle bar and thread take-up mechanism

1)	Attach the thread take-up	0	to the arm using the thread take-up support shaft	@,and tighten the set
	screw@.
2)	Insert the needle bearing	0	into the thread take-up 0. Holding the washer €)	with one hand, insert

the needle bar crank @ into the thread take-up 0, the needle bearing 0, and the washer €), and then tighten the two set screws fi so that they are aligned with the screw flats of.the needle bar crank@.

3)Attach the oil cap@.

4)Insert the needle bar crank rod @) into the needle bearing «!>,and secure them using the screw (lefthand screw) ID.

NOTE: The needle bearing«!> is not used for the thick material specification.

5) Pass the needle bar guide slide block 0 through the needle bar guide of the machine arm, and insert the tip of the needle bar clamp@.

6)Insert the needle bar 4D into the arm from the top of the machine, pass it through the needle bar clamp @,and temporarily tighten the screw~.

7)Attach the oil cap@.

8) Attach the needle bar thread guide 0 and the needle tiD to the tip of the needle bar ID, and secure the

setscrew@.

3-1

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~Intermittent presser foot mechanism

1)Slide the guide part of the presser bar clamp 0 into the arm channel. Insert the presser bar @ into the arm from the top of the machine head. Then temporarily tighten the screw @. (The screw hole of the

	presser bar@ should be facing toward the front.)
2)	Insert the intermittent lever 9 along with link (L) 0 into the shaft of the presser bar clamp	0, then
	secure the roller shaft ®.
3)	Fit the U-UD feed lifter lever roller f'J into the roller shaft @, attach the intermittent guide	@ to the
	arm, and temporarily tighten the bolt@.

4)Move the presser bar@ up or down until it moves smoothly, and attach the intermittent guide @ to the presser bar@ using the bolt@.

5) Insert the shaft of the intermittent support assembly ® into needle bar crank bush (R), and put the intermittent support assembly® into the U-U D feed lifter lever roller ID.

6)Attach the set collar 0, and tighten the set screw®.

7)Place the stop ring ID on the roller shaft@.

8) Attach link (L) 0 to U-UD feed arm (L) (f) using the stud screw@.

9)Place the washer (ID on the presser bar @. Insert the spring @ and the spring guide f1i). Tighten the adjust screw m.

10) Attach the presser foot @) to the presser bar @ using the screw @.

3-2

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@)Thread trimmer mechanism

1)Attach the thread trimmer cylinder @ to the bed using the support lever shaft 0, and tighten the set screw@.

2) Attach the two air tubes a to the two elbows €) of the thread trimmer cylinder@.

3)Place the movable knife holder@ on the bed, and attach the washer fi and the stop ring@).

4)Attach the thread trimmer connecting rod@ to the thread trimmer cylinder@ using the bolt@).

5) Attach the thread trimmer connecting rod ® to the movable knife holder @ using the stud screw 0).

Make sure that the movable knife holder@ moves smoothly.

6)Attach the lower thread finger@ using the screw@.

7)Attach the movable knife@ to the movable knife holder@ using the two screws ID.

8)Insert the fixed knife~ into the bed, and then tighten the screw tTl.

9)Attach the fixed knife presser tiD using the two bolts @.

3-3

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[4]Bottom mechanism

1)	Attach the bottom cylinder 0 to the cylinder support shaft@ using the washer@) and the stop ring 0.
2)	Fit the bottom lever @} into theY-type fitting 0 of the bottom cylinder 0 1 and secure them using the
	link pin fi and the stop ring@.
3)	Pass the bottom lever	@} through the belt shift bar @ 1 and secure them using the washers «!> and 0),
	and the stop ring @ .
4)	Fit the two air tubes t0	on the MS elbows@ of the bottom cylinder 0.

3-4

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~Rotary hook mechanism

		The center of the needle		The center of the needle
1)		Temporarily attach the rotary hook 0 to the rotary hook shaft@) using the three set screws@.
2)		Attach the rotary hook bobbin case holder 9 to the bed using the screw@.

3)Turn the pulley to raise the needle 2.2 mm from its lowest position. Tighten the three set screws @ so that the rotary hook @) point is aligned with the center of the needle. Adjust the clearance.between the rotary hook point and the needle to 0.01 - 0.08 mm.

4)Turn the pulley to align the rotary hook point@) with the center of the needle. Loosen the set screws fi ..

Adjust the position of the needle bar by moving it vertically so that the clearance between the upper end of the needle hole and the rotary hook point@) is as follows:

<Distance from the upper end of the needle hole to the rotary hook point> Rotary hook {B 1) {S29785-001){for medium thick material) 0.5- 1.5 mm

Rotary hook {BR) {S27851-001){forthick material) 1.0-2.0 mm

Rotary hook {BRTR) {531739-001 ){for extra thick material) 1.0- 2.0 mm

3-5

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[§]Needle plate mechanism

I

I

I

t~i~

I

1)Loosen the bolt 0 1 and pull the needle plate support bracket@ out.

2)Temporarily attach the needle plate support bracket@ using the four bolts@).

3)	Temporarily attach the four needle plate supports G and the two needle plate supports (B) 0 to the
	needle plate support brackets @, and tighten the bolts @ from the underside of the needle plate
	support bracket@.
	NOTE: For the BAS-3751	temporarily attach the needle plate support side	f)	to the needle plate
	support 0 using the bolt@.
4)	Put the needle plate left	@,the needle plate inner ([i) 1 and needle plate right	ID	on the needle plate
	supports, and tighten the screws after adjusting the screw holes.
5)	Fully tighten the bolts 0, @), @, and @.

3-6

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[l]Covers

1)	Attach the eye guard 0	and the face plate@ using the respective screws.
2)	Attach the arm rear cover @)I the arm front cap 0 I and the arm motor cover 0 using the respective
	screws.
3)	Attach the dust belt@	and the belt presser plates 6 to the X-hold frame@.

4)Attach tables (A)@ I (B) tiD I (C) ID I and (D) 0 I using the bolts. NOTE: Insert the earth plate@ under table (C) ID.

5)Insert the operation box assembly minto table (C) ID I and tighten the nut@.

6)Attach the two table covers@ using the screws.

7)Attach the front cover 0 I the side covers@, and the rear cover@ using the respective screws.

3-7

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