Switch Board Replacement, Procedure | Lincoln Electric SVM101-B

TOC

F-56

TROUBLESHOOTING & REPAIR

F-56

SWITCH BOARD REPLACEMENT (cont.)

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NOTE: If a test indicates that a Switch Board is defec- tive, unless their part number is L10958-[ ] both Switch Boards must be replaced at the same time. In addition to replacing the Switch Boards, Capacitors C1 and C2 (plus C14 and C15 on 575 VAC models) must also be replaced if the following conditions exist:

a.The part number of the Switch Boards is something other than L10985-[ ]

b.The machine was operating from 380 VAC or high- er when the failure occurred.

c.Burned areas are visible on the Switch Boards.

PROCEDURE

1.Perform the Input Filter Capacitor Discharge

Procedure.

2.Remove the Switch Board assembly from the machine as directed in the CAPACITOR

REPLACEMENT PROCEDURE.

3.Remove the four socket head screws that hold the Switch Board to the heat sink.

4.Remove the 1/4”-28 hex head capacitor mounting screws.

5.Remove the Switch Board from the heat sink.

6.Clean the heat sink surfaces thoroughly to remove all the heat sink compound. During machine oper- ation, this compound helps conduct heat from the PC board to the heat sinks.

7.Apply a thin layer (.002”) of Dow 340 or Penetrox A13 Heat Sink Compound to the mounting sur- faces of the new PC board and to the Capacitor terminals. DO NOT allow the compound to enter the mounting screw holes because it can distort the torque values.

8.Prepare to mount the new PC board on the heat sink by first lining up the mounting holes. Then press the PC board into place.

9.Insert each of the four socket head screws into the mounting holes and thread finger tight. The threads are soft — be careful not to cross thread the screws.

10.Loosen the capacitor mounting bracket tightening screw. See Figure F.28.

11.Torque both sets of screws in 10 inch-pound incre- ments using a diagonal tightening sequence. Torque the four socket head screws to 44 inch- pounds (5 Nm). Torque the two hex head capaci- tor screws to 55 inch-pounds (6 Nm).

12.Tighten the capacitor mounting bracket mounting screw

13.Remount the assembly into the machine

14.Reconnect all the leads to the PC board. Double check that each lead is connected to the correct terminal. Failure to reconnect the leads correctly can result in machine damage when the power is applied.

15.Perform the Test After Repair of Switch Boards and/or Capacitors.