Replacement Procedures; Switch Board Replacement - Lincoln Electric INVERTEC V300-PRO SVM105-B Service Manual

F-56
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.
TROUBLESHOOTING & REPAIR
SWITCH BOARD REPLACEMENT (cont.)
V300-PRO
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.
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.
F-56
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