ESAB LAW 400, Service Manual

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DESIGN CHANGES
Below is a short description of design changes made to the LAW machines. The details you
find in the previous chapters of this manual.
Changes introduced with effect from machine no. 512 . . . . . .
1. Speed control of the fan: see items C6, KM2, and ST2 in the component description and
items 324 and 325 in the spare parts list.
2. The position of the thermal overload cutout has been changed: see item 6 in the
component description and items 303, 307 and 413 in the spare parts list.
3. Seals have been incorporated in screw holes: see item 118 in the spare parts list.
4. The design of the mains cable bushing has been changed: see item 119 in the spare parts
list.
5. A seal has been fitted to the cooling water filler: see item 223 in the spare parts list.
6. The digital display instrument accessory now contains necessary connection components
for the LAW and the MEK 4. The part numberof the display instrumenthas been
changed: see accessories list item 1 and item 213 in the spare parts list.
7. A new thyristor bridge has been introduced for the LAW 400: see the fitting instructions
for the thyristor modules and items 410, 413--416 and 418--421 in the spare parts list.
8. A new circuit board carrying program version P1.02 has been introduced, with the
following feature changes:
* Mains voltage compensation has been introduced: see item 4 in the function
description.
* The hot start function has been changed: see item 13 in the function description.
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The arc voltage input has been changed to enable the arc voltage to be measured be-
tween the welding wire and one welding terminal. Compare items 7a and 7b in the
function description
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Functions for the MEK 4S:
-- An input for a wire feed reference has been introduced (board connector H3).
-- A presetting input has been introduced (board connector H7).
See item 4 in the function description.
* Test routione L20 has been introduced: see the test routine description.
Machines with serial numbers 434 . . . :
The new circuit board (part no. 0486 291 880) can be used in these machines.
Functions marked with an asterisk ( *) will operate when the board is replaced. If the
functions marked with a bullet (
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)
are to work, changes must be made to the machine’s
wiring.
Machines with serial numbers 512 . . . :
The old circuit board (part no. 0486 220 880) should not be used in these machines.
Three new drawings have been introduced to take account of the design changes:
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Wiring diagram LAW 400/500 400--415 V, for machines from and including no. 512 . . .
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Wiring diagram LAW 400/500 230--500 V, for machines from and including no. 512 . . .
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Component positions diagram for circuit board AP1 486 291--880