Troubleshooting & repair – Lincoln Electric INVERTEC SVM129-B User Manual
Page 114
TROUBLESHOOTING & REPAIR
F-76
F-76
INVERTEC® STT® & STT® II
OUTPUT RECTIFIER REMOVAL AND REPLACEMENT (continued)
FIGURE F.41 – SWITCH BOARD/CAPACITOR ASSEMBLY THROUGH-BOLTS
THROUGH-BOLTS
11. Using the 3/8" nut driver, remove the rear
nuts and washers from the switch
board/capacitor assembly through-bolts.
See Figure F.41.
12. Using the 3/8" nut driver, loosen the front
nuts from the switch board/capacitor
assembly through-bolts.
13. Carefully lift the horizontal baffle away
from the upper tabs of the output rectifier
heat sink assembly.
14. Slide the heat sink assembly to the right
(facing the back of the machine) to disen-
gage the bottom tabs from the lower hori-
zontal baffle.
15. Carefully remove the output rectifier heat
sink assembly and leads from the STT
machine.
16. Remove the nut that secures each diode
that is to be replaced.
NOTE: The output diodes must be replaced in
matched sets.
17. Before mounting the new diode sets, clean
and brighten the mounting surfaces of
both the diode sets and the heat sink with
fine steel wool.
18. Apply an even coating of DOW Corning
340 Heat Sink Compound to the mounting
surfaces of the diodes that contact the
heat sink. This compound layer should be
less than .001 inch thick. DO NOT apply
the compound to the diode studs or
mounting nut threads.
19. Insert the diode sets into the mounting
hole and tighten the diode mounting nuts
to a torque of 25 inch-pounds (3 Nm).
20. Replace the rectifier heat sink assembly,
leads and connections that were previous-
ly removed. Install the fan and motor
assembly (note insulation placement).
Install the case back and the case wrap-
around cover.