Troubleshooting & repair, Continued), Scr heat sink assembly removal – Lincoln Electric SQUARE WAVE TIG 255 SVM100-A User Manual
Page 84
SQUARE WAVE TIG 255
F-43
TROUBLESHOOTING & REPAIR
SCR HEAT SINK ASSEMBLY REMOVAL
(continued)
TEST PROCEDURE
1.
Remove main power supply to machine.
2.
Remove case sides and top.
3.
Locate SCR heat sink assemblies.
4.
Remove all gate, snubber and cable
leads from the SCR heat sink assembly
that is to be serviced.
5.
Remove the four 1/4”-20 hex nuts and
associated plain and lock washers from
the four 1/4”-20x1.75” hex head cap
screws. Remove the heat sink assem-
bly trying not to disturb the insulating
washers and bushings. See figure
above.
6.
Reinstall the heat sink assembly in the
same manner being certain that the
insulating washers and bushings are
installed correctly. See figure above.
7.
Test with an ohmmeter to make certain
that the heat sink assembly is electrical-
ly isolated from chassis ground by at
least 500,000 ohms of resistance.
8.
Reconnect the gate leads.
9.
Reconnect the snubber and cable leads
using a thin coating of Dow 340 heat
sink compound on the connection sur-
faces. Be sure that the connection sur-
faces are clean and free from any dirt or
paint.
SCR Heat
Sink Assemblies