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W ire feed unit
0740 800 126
9905
MLC 30C
Service manual
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LIST OF CONTENTS Page
READ THIS FIRST 3................................................................
COMPONENT DESCRIPTION 4......................................................
CONNECTION DIAGRAM 5..........................................................
DESCRIPTION OF OPERATION 6....................................................
1 Power supply 7................................................................
2 Start / Stop 8..................................................................
3 Gas valve 8...................................................................
4 Motor driving / braking 9........................................................
5 Pulse generator input 10.........................................................
6 Can bus 10....................................................................
7 Arc voltage sensing 12..........................................................
SERVICE FUNCTIONS 12............................................................
TERMINATION RESISTANCE 12......................................................
TECHNICAL DATA 13................................................................
INSTRUCTIONS 14..................................................................
INTRODUCTION 14.................................................................
Delivery contents 14................................................................
INSTALLATION 14..................................................................
Connection 14.....................................................................
OPERATION 15.....................................................................
Settings 15........................................................................
Changing the wire 16...............................................................
Welding 17........................................................................
MAINTENANCE 19..................................................................
Cleaning 19.......................................................................
ACCESSORIES 19..................................................................
SPARE PARTS LIST 21..............................................................
NOTES 31..........................................................................
Rights reserved to alter specifications without notice.
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READ THIS FIRST
Maintenance and repair work should be performed by an experienced person, and electrical
work only by a trained electrician. Use only recommended replacement parts.
This service manual is intended for use by technicians with electrical/electronic training for
help in connection with fault--tracing and repair.
Use the connection diagram as a form of index for the description of operation. The circuit
board is divided into number ed blocks, which are described individually in more detail in
the description of operation. All component names in the connection diagram are listed in
the component description.
This manual contains details of all design changes that have been made up to and i ncluding
May 1999.
The MLC 30C is designed and tested in accordance with European standard EN
60974--1 and EN 50199.
On completion of service or repair work, it is the responsibility of the person(s) etc.
performing the work to ensure that the product does not depart from the requirements
of the above standard.
WARNING
READ AND UNDERSTAND THE INSTRUCTION MANUAL BEFORE INSTALLING OR OPERATING.
ARC WELDING AND CUTTING CAN BE INJURIOUS TO YOURSELF AND OTHERS. TAKE PRECAU -
TIONS WHEN WELDING. ASK FOR YOUR EMPLOYER’S SAFETY PRACTICES WHICH SHOULD BE
BASED ON MANUFACTURERS’ HAZARD DATA.
ELECTRIC SHOCK -- Can kill
S Install and earth the welding unit in accordance with applicable standards.
S Do not touch live electrical parts or electrodes with bare skin, wet gloves or wet clothing.
S Insulate yourself from earth and the workpiece.
S Ensure your working stance is safe.
FUMES AND GASES -- Can be dangerous to health
S Keep your head out of the fumes.
S Use v entilation, extraction at the arc, or both, to keep fumes and gases from your breathing zone and
the general area.
ARC RAYS -- Can injure eyes and burn skin.
S Protect your eyes and body. Use the correct welding screen and filter lens and wear protective
clothing.
S Protect bystanders with suitable screens or curtains.
FIRE HAZARD
S Sparks (spatter) can cause fire. Make sure therefore that there are no inflammable materials nearby.
NOISE -- Excessive noise can damage hearing
S Protect your ears. Use ear defenders or other hearing protection.
S Warn bystanders of the risk.
MALFUNCTION -- Call for expert assistance in the event of malfunction.
PROTECT YOURSELF AND OTHERS!
WARNING!
Rotating parts can cause injury, take great care
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WARNING !
STATIC ELECTRICITY can damage circuit
boards and electronic components.
S
SS
S Observe precautions for handling electrostatic
sensitive devices.
S
SS
S Use proper static--proof bags and boxes.
ESD
COMPONENT DESCRIPTION
AP01 The main circuit board, with control electronics. See the description on
page 7.
AP02 Circuit board, contact interfacing.
C1 -- C5 Capacitor, 0.1←F
M1 Motor, r ated voltage 42V.
P1 Pressure regulator with filter.
PC1 Pulse generator, included in motor M1.
SB1 Pneumatic air flow relay.
XP01 12--pole connector, for connection to the power unit.
XP02, XP03 D--SUB connector.
XS01 -- XS17 Sleeve connector.
YV1 Solenoid valve.
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CONNECTION DIAGRAM
Numerals 1 to 7 (inclusive) refer to the description of operation.
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DESCRIPTION OF OPERATION
Component positions, circuit board AP01
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Circuit board AP01 is screened by a can that is connected to 0V in the wire feed unit.
The circuit baord has an inbuilt discharge circuit for the filter capacitor (C52), the discharge
time is about one minute. Wait this time before removing the screening box from the circuit
board. Also make sure that the capacitor is discharged before the screening box is fitted on
the circuit board.
1 Power supply
The wire feed unit receives a 42V supply from the control power supply transformer
in the power unit via contact XP01. At full load, it consumes about 2A.
S AC power supplies
The 42V AC supply powers transformer TR1 and is used as the power supply to the
gas valve.
Transformer TR1 has two secondary windings, each of which supplies 17V. The two
supplies, A_17V and B_17V, supply the welding torch contact.
S DC power supplies
Diodes D13 -- D16 rectify the 42V supply to 60V. Capacitor C52 smooths the
supply, which is then used to power the wire feed motor. When the power is
switched off the capacitor is discharged by a number of paralell connected resistors.
Diodes D35 -- D38 rectify the 17V supply. Voltage regulators VR1 and VR3
regulate the 20V supply to 5V and 15V respectively.
S Power supply monitoring
Potential divider R4/R5 monitors the voltage from transformer TR1. The voltage
across R5 is normally about 1.8V. If the voltage drops by 30% or more, then the
voltage across R5 drops to 1.25V or less. The reset circuit (IC12) supplies a warning
signal to the processor, which stops the wire feed and then all communication on the
bus. The display of the setting unit shows error code 4.
If the 20V supply drops below 15V or rises above 25V, the display shows error code
9, but no functions are turned off or blocked.
If the 15V supply drops below 13V or rises above 17V, the display shows error code
8, but no functions are turned off or blocked.
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2 Start / Stop
SB1 is an air flow relay, the relay contact is supplied at 17V AC from transformer
TR1. When the welding torch trigger is activated and air flows through the relay the
relay contact closes. SB1 activates optocoupler IC7, pulling down the voltage across
C47. The wire feed motor starts and the power source gives output voltage.
If welding does not commence within three seconds from the star t of wire feed the
power source switches off the voltage. The wire feeding continues until the feed
speed is lower than the programmed stop speed, see Welding on page 17.
3 Gas valve
The gas valve is connected to board contacts G3 and G4. Connectors XS04 and
XS15 are not used in the MLC 30C.
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4 Motor driving / braking
Principal diagram for the motor drive circuits
S Driving
The wire feeder is run by a series motor with falling characteristic. The motor is
constant current controlled.
The smoothed +60V supply powers the motor. Pulse width modulation of transistor
Q4 varies the effective motor voltage. The pulse frequency is 15.6kHz. The
maximum pulse conduction time is 97% of the pulse cycle time. During t he pulse
off periods, the motor freewheels through freewheel diode D27.
The feed roller’s speed at the maximum wire feed speed of 18 m/min is 273 r/min.
S Current monitoring
Resistor R114 provides a signal that is proportional to the motor current.
The current limit is set by a reference voltage from the microprocessor. The current
limit is manually programmed when the selection of welding wire is made, see item
8onpage16.
When the current exceeds the actual current limit, IC14:2 turns off the gate pulses to
Q4. When the current falls, Q4 conducts again at the next gate pulse.
S Braking
When the motor starts, capacitor C67 is charged via diode D31, although the voltage
is limited to 15V by zener diodes D33 and D34.
When the motor is to brake, optocoupler conducts and connects capacitor C67 (at
15V) to the gate of transistor Q2. This conducts and short-- circuits the motor supply
via resistors R71 and R79, which limit the current to about 20A.
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5 Pulse generator input
Pulse generator input
Pulse generator PC1 is fitted inside the case of motor M01. At a wire feed speed of
18 metre/minute, the pulse frequency is 409Hz.
Input E3--E4 is used for motors with tachometer. MLC 30C does not use this input.
When the pulse generator input is used pin 9 of IC4 is pulled to a high level (+5V)
by transistor Q9.
6 Can bus
IC2 manages communication for the electronics on the feed unit circuit board.
If the PTC resistors R2 and R3 not are fitted the links BY1 and BY2 replaces them.
The +12V supply is the power supply from the power unit to the setting unit, and is
not used on the wire feed unit circuit board. 0V on the wire feed unit circuit board is
connected to 0V on the setting unit.
Start sequence
The circuit board carried an EEPROM, IC16. (EEPROM = Electrically Erasable
Programmable Read--Only Memory. ) IC16 is the key to operation of the board.
LEDs on circuit board
A
P
01
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On power--up, the circuit board’s CAN controller reads in the following parameters
from IC16: The bus speed (400 kbit/s), the node address (3 for the wire feed unit)
and the machine identification (7 = MLC 30C).
The bus speed, the node address and the machine ID are programmed into IC16
during testing of the board.
Four LEDs gives the possibility to follow
the start sequence when powering up the
unit.
LED1 is lit first, then LED2, after that
both LEDs are switched off.
When all LEDs are off the board is
initiated and the application programme
runs.
During upgrading the software with a PC
card LED3 and LE D4 are lit.
At normal operation all four LEDs are
switched off.
Problems with CAN communication
The setting unit displays fault code 17 if communication between it and the wire
feed unit is not working.
Check the following in the event of problems with CAN communication:
S The terminating resistance: see instructions on page 12.
S The control cable:
Check that the right type of cable is used. This must be the same type as on the
setting unit and between the power unit and the wire feed unit when delivered.
Check that each signal is connected to the correct wire. CAN high and CAN
low must run on the twisted pair.
S All Screen connection must make good electrical contact.
S MLC 30C: Good contact at the connections to capacitors C1, C2 and C3. See
the main circuit diagram on page 5.
S LUD: Good contact at the connections to capacitors C1, C2, C5 and C8 as well
as the chassis connection of circuit board AP2. See the main circuit diagram for
the LUD.
S The power supplies to the feeder unit circuit board AP01.
S If none of the points above solves the problem, replace AP01.
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7 Arc voltage sensin g
To avoid the voltage drop in the main welding current cables, the power unit senses
the arc voltage via the welding wire and the wire feed unit motor. The arc voltage is
filtered by capacitor C80 on the circuit board.
SERVICE FUNCTIONS
A number of service functions can be accessed via the setting unit. The service functions
have several applications over and above service and fault--tracing. Those that ar e of
importance for service and fault--tracing are described in the LUD 320/450 service manual.
TERMINATION RESISTANCE
The termination resistance must be connected to the ends of the CAN bus to prevent
communication problems. The setting unit has a built--in terminator, but the power source
and wire feed unit do not. The termination resistance is supplied with the power source.
Depending on the connection case, the resistance is connected as follows:
Termination resistance
Termination resistance
Setting unit connected to the wire feed unit
Connect the termination resistance to the
rear of the power source. Connected in this
way on delivery
Setting unit connected to the power source
Connect the termination resistance to the
front of the wire feed unit
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TECHNICAL DATA
The MLC 30C wire feed unit is intended to be used with the LUD 320 and LUD 450 power
units.
Supply voltage 42 V 50/60 Hz
Power consumption 70 VA
Gas connection Hose nipple for 6 mm hose
Air connection Connection for 1/4” hose
Air pressure Min. 500 kPa (5 kg/cm
2
)
Wire feed speed 1.5 -- 18 m/min
Wire diameter 0.8 -- 1.6 mm
Welding torch PKB, hose lengths up to 16 m
Welding current Max 400 A at 60% duty cycle
Inlet nozzle Hole diameter 2.7 mm
Outlet nozzle Hole diameter 1.5 mm
Remove the outlet nozzle when welding with 1.6 mm wire.
Brake hub intended for
wire reel with:
Max. outer diameter 300 mm
Hub core 51.1 mm
Hub length 100 mm
Dimensions (l x w x h) 493 x 336 x 268 mm
Enclosure class IP21
Continuous A--weighted
noise pressure level 58 dB
Weight 22 kg
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INSTRUCTIONS
This chapter contains an extract from the instruction manual for MLC 30 C.
INTRODUCTION
The MLC 30C wire feed unit is a part of ESAB’s Aristo 2000 system. The wire feed unit
pushes the wire through the welding hose to the welding torch and the pneumatically--oper-
ated motor in the torch piston draws the wire to the contact tip. This ensures smooth and
even wire feeding, excellent for welding with soft wires (e.g. aluminium) and fine wire
dimensions.
The welding wire is isolated from the wire feed unit’s outer casing.
The wire feed unit can be placed in different positions. Equipped with a turning piece, the
MLC 30 C can be placed so that it pivots above the power source pilot. It can also be fitted
with a suspension unit so that it can be suspended above the workplace, or it can be
complemented with a set of wheels (trolley) so that it can be maneuvered on the floor or on a
workbench.
Delivery contents
The wire feed unit is delivered with the following accessories:
Inlet nozzles for the PKB welding torch
Nozzles for 0.6, 0.8, 1.0, 1.2 and 1.6 mm Ss and Fe wire.
Nozzle for 0.8 -- 1.2 mm aluminium wire.
Feed rollers
For 0.6 -- 1.0 mm and 1.0 -- 1.6 mm wire.
INSTALLATION
WARNING
This product is intended for industrial use. In a domestic environment this product may
cause radio interference. It is the user ’s responsibility to take adequate precautions.
Connection
Connections and control panel
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1. Nipple for gas connection.
2. Connection for control cable from power source.
3. Connection for welding current from power source.
4. Connection for setting unit, optional connection. Only setting unit PUA 1 or termination
resistance can be connected here.
5. Connection f or welding torch.
6. setting unit.
S Connect compressed air to the hose on the back of the wire feed unit.
Connecting welding hose
1. Press the inlet nozzle (a) (selected according to the
size of the electrode) into the welding hose.
2. Open the wire feed unit on the side where the feeder
mechanism is located. Undo the locking screw in
the connection plate.
3. Connect the welding hose (b) to the wire feed unit
and tighten the locking screw in the connection
plate.
4. Remove the plastic cover on the welding torch
housing. Undo locking screw (e) press the other end
of the hose into the torch. Tighten the l ocking screw
and replace the plastic cover.
Connecting welding current
Connect the welding cable from the power source’s positive pole to the current connection on
the back of the wire feed unit.
Connecting compressed air
Connect compressed air (at l east 500 kPa) to the hose that sticks out of the back of the wire
feed unit.
The air goes to a filter regulator that is pre--set at 500 kPa. The regulator drains itself when
the compressed air is turned off.
Note! Check regularly that the regulator’s draining function is working properly. Water
present in the compressed air entering the welding torch will result in operating problems.
OPERATION
Settings
The wire feed unit does not have a control panel. Settings are made using the setting unit,
which can be connected to the wire feed unit or the power source. The setting unit must have
S = Adjustment screws
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software version 2.20 or a later version. A progr amming handbook that describes how the
setting unit should be handled accompanies the setting unit.
The setting unit menues f or the MLC 30C does not include the following functions: remote
control, 4--stroke, gas pre flow, hot start and crater filling. The four last mentioned functions
are available by using the welding torch to modify the start and stop sequences.
Brake hub
The electrode reel is located on a brake hub, it is
adjusted upon delivery. If you need to make a follow--up
adjustment, follow the instructions below.
The brake action can be adjusted using the two screws (the
springs) that ar e located inside the hub. Turn the screws
clockwise to reduce the brake action. Adjust the hub so that the
wire is somewhat slack when feeding stops.
Cold wire feed
If you start the wire feed, the power source produces a voltage and the gas valve opens. If the
wire does not come into contact with the workpiece, the voltage and gas are shut off after
approx. three seconds. The wire feed continues until you release the trigger.
Wire feed pressure
The wire feed unit has a driving feed roller and a free-- wheeling pressure roller. The pressure
roller is located in an axle mounted in bearings. The pressure on the wire can be changed by
means of a spring attached to the shaft, which can be adjusted to different positions.
WARNING!
Rotating parts can cause injury, take great care
Changing the wire
The wire liner is made of plastic and is sensitive to sharp objects. File away sharp burrs and
edges on the wire tip before the new welding wire is inserted into the wire liner.
1. Loosen the pressure roller’s spring in the wire feed unit and torch.
2. Retract the remaining wire out of the wire liner. Remove the reel.
3. Insert the new reel.
4. Straighten out 5--10 cm of the wire and file away the burrs on the tip of the wire.
5. Check that the following components have the right dimensions: feed roller, outlet
nozzle, the welding hose inlet nozzle and the welding torch contact tip.
6. Insert the wire into the wire feed unit. Make sure that it sits correctly in the feed roller’s
groove and in the outlet nozzle. When welding with 1.6 mm welding wire the outlet
nozzle must first be removed. Insert the wire approx. 10 cm into the welding hose.
7. Set the pressure roller’s spring to position 1, see the picture
on the right.
Set the pressure on the welding torch’s pressure roller in accordance
with the table below.
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Place the welding hose as straight as possible.
8. Start the power source. Select motor power 1 A for the feed motor
if the wire diameter is 0.6 -- 1 mm. For thicker wires, select the
motor power as indicated in the table below. (The following motor
power settings are available 1.0 - 1.25 - 1.5 and 1.75 A)
Use the setting unit to set the motor power. Start from the main
menu and select the following functions:
AUXLIARY FUNCTIONS, CONFIGURATION, MIG/MAG DEFAULTS, MLC 30C,
MOTOR POWER.
Mark and select the desired motor power.
9. Press in the torch trigger as far as it will go, let the wire feed through the welding hose
and out through the contact tip.
If the motor does not have the capacity to feed the wire, increase the motor power one
step.
10. Set the correct feed pressure and motor power in accordance with the table below.
11. Check that the brake hub is correctly adjusted, see 5.1.1 on the previous page.
IMPORTANT!
To prevent the reel sliding off the hub: Lock the reel in place by turning
the red knob as shown on the warning label attached next to the hub.
Recommended settings
This table applies to PKB welding torches with 5, 10 and 16 metre hose length.
Wire type
(mm)
PKB inlet nozzle
Lining Marking Ordering no.
Wire pressure
MLC PKB
Motor power
MLC (A)
AIMg 0.8--1.0 Plastic 0.8/0.3 0258 002 585 3 min 1.25
AIMg 1.2 Plastic 0.8/0.3 0258 002 585 4 mean 1.25--1.5
AISi 1.0 Plastic 0.8/0.3 0258 002 585 3 min 1.25
AISi 1.2 Plastic 0.8/0.3 0258 002 585 4 min 1.25
Fe 0.8 Steel 0.8/0.3 0258 005 581 5 mean 1.25--1.5
Fe 0.9 --1.0 Steel 1.0/0.4 0258 002 582 5 mean 1.25--1.5
Fe 1.2 Steel 1.2/0.5 0258 002 583 4 mean 1.5
Fe 1.4 --1.6 Steel 1.6/0.6 0258 002 584 5 mean 1.5
Ss 0.8 Steel 0.8/0.3 0258 002 581 5 mean 1.25--1.5
Ss 1.0 Steel 1.0/0.4 0258 002 582 5 mean 1.25--1.5
Ss 1.2 Steel 1.2/0.5 0258 002 583 5 mean 1.5
Weld ing
For best welding results, you should use the synergic mode. It is also possible to use
independent settings (manual settings). The description below is applicable for the synergic
mode.
Set and adjust the wire feed unit for the particular wire that you will use, see 5.2 above. Then
make the following settings:
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1. Set the stop wire speed. This is the wire feed speed when the power source is shut off
(and the feed motor stops). If you have selected a stop speed that is too low, the wire
burns up in the contact tip. If the speed is too high, you end up with too long “stick out“
and/or involuntary welding stoppage.
The setting unit is used to set the stop speed. Start in the main menu and select the
following functions:
AUXILIARY FUNCTIONS, CONFIGURATION, MIG/MAG DEFAULTS, MLC 30C, STOP
WIRE SPEED.
The stop speed can be set between 0.7 and 10 metres per minute.
Example: If the wire feed speed is 13 m/min or more, the stop speed should be approx.
10 m/min. I f the feed is 3 to 4 m/min, the stop speed should be approx. 1 m/min.
2. Set the start data. When you start welding, the power source needs information about the
wire feed speed to be able to provide the appropriate current. The power source takes the
relevant speed data from the wire feed unit approx 1.3 seconds after the start of welding.
To obtain a good start, it is important that the start data does not deviate too much from
the actual speed. There are four ways to set the start data:
a. Select
MEASURE from the main menu and cold wire feed for at least 2 seconds.
The wir e feed speed that is shown last is stored as start data.
b. Select MEASURE from the main menu and set the wire speed using the setting unit.
c. Select SET from the main menu and set the wire speed using the setting unit.
d. Recall your start data from a memory position where you have previously stored
them.
If you do not change the start data, then the last used start data will apply to the next
welding start. (The setting unit always stores t he start data in memory position 95, from
which the data is recalled at each start.)
3. Start welding.
a. First, press in the welding torch trigger for approx. one second so that air starts to
flow. This produces gas pre--flow and activates the power source. Do not press the
trigger so much so that the wire starts to be fed out.
b. Thereafter, press harder so that the wire feed starts and welding is begun.
c. Once welding has started, the power source detects the wire speed and regulates the
voltage accordingly.
d. If you want to use the crater filling function when you stop welding, you reduce the
wire speed gradually before the end of welding. In this case, you have to set the stop
speed somewhat lower than that stated in point 1. above.
e. Once welding has stopped, the power source restarts after 0.4 seconds. It is then
activated for approx. 2 seconds. This function ensures that you can quickly restart,
e.g. when spot--welding.
4. Do not change settings or the controller menu display during welding or wire feeding.
This can cause interruptions in welding, in which case the controller will display error
code 23.
In the welding torch’s instructions for use, you will find more inf ormation about how you can
regulate the wire speed with the torch.
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MAINTENANCE
Note:
All warranty undertakings given by the supplier cease to apply if the customer attempts
to rectify any faults on the machine during the warranty period.
Cleaning
Regular maintenance is important for reliability and safe operation.
Wire feed unit
Keep clean and replace the feed mechanism’s wear parts at regular intervals.
Note that if the pressure on the pressure rollers is too great, this can cause abnormal wear and
tear on the pressure roller, feed roller and wire liner.
Welding torch
Blow clean the wire liner regularly and clean the gas nozzle.
Dismantling when cleaning:
1. Detach the screw in the connection block using an Allen key. Remove the welding hose.
2. Detach the two stop screws that hold the inlet and outlet nozzles in place and remove
them.
3. Refit in the reverse order.
ACCESSORIES
Connection kits: power source - wire feed unit
Order no. Designation
0456 528 880 Connection kit, 1.7 metres
0456 528 881 Connection kit, 8 metres
0456 528 882 Connection kit, 16 metres
0456 528 883 Connection kit, 25 metres
0456 528 884 Connection kit, 35 metres
Other accessories
Listed in the list of spare parts.
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