Troubleshooting & repair – Lincoln Electric POWER WAVE SVM173-A User Manual

Page 130

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TROUBLESHOOTING & REPAIR

F-84

F-84

POWER WAVE 455M/MSTT

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OUTPUT RECTIFIER, STT CHOPPER BOARD AND RECTIFIER MODULE

REMOVAL AND REPLACEMENT (CONTINUED)

RECTIFIER MODULE REMOVAL AND
REPLACEMENT PROCEDURE

1. Using the 9/64” allen wrench, remove the

cap screw from the center of the rectifier
module that is to be replaced.

2. Using the 7/16” wrench, remove the two

mounting bolts and associated washers
from the rectifier module to be replaced.

3. Remove the faulty module.

4. This module requires special mounting con-

siderations to prevent warping of the base
plate. The heat sink surfaces must be clean
and flat. Apply a thin, even coating of ther-
mal compound, (Penetrox A13) 0.004 to
0.010 inches thick. Keep the compound
away from the area of the mounting holes.

5. Press the new module firmly against the

heat sink while aligning the mounting holes.
Start all three screws two to three turns by
hand.

6. Tighten each of the outer screws to between

5 and 10 in-lbs.

7. Tighten the center screw to between 12 and

18 in-lbs.

8. Tighten each of the outer screws again, this

time to between 30 and 40 in/lbs.

RECTIFIER ASSEMBLY REPLACE-
MENT PROCEDURE

1. Position the assembly in place with the

mounting bolts.

2. Assemble the nuts and associated wash-

ers to the mounting bolts.

3. Using the 7/16” wrench, tighten the four

nuts on the mounting bolts.

4. Replace leads #292 and #291 to the ther-

mostat.

5. Connect plug J10 to the STT Chopper

Board.

6. With the 7/16” wrench, attach lead #287

from the STT Snubber Diode D5.

7. With the 7/16” wrench, attach lead #289B

from the STT Snubber Capacitor C10.

8. Connect the eight transformer leads to the

correct rectifier modules. Tighten the
screws (with two flat washers and one lock
washer) to between 30 and 40 in/lbs. Do
not stress the terminals when making
these connections.

9. Apply a thin coat of Penetrox A13 to the

heat sink where the Power Wave positive
output lead and the STT output lead attach.

10. Attach the Power Wave positive output

lead to the heat sink using the 9/16”
wrench.

11. Attach the STT output lead to the heat sink

using the 7/16” wrench.

12. Install the case top and sides using the 3/8”

nut driver.

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