Lincoln Electric PRECISION TIG SVM186-A Service Manual page 83

F-43
REMOVAL AND REPLACEMENT PROCEDURE (continued)
16. With the 3/8" wrench remove the four mount-
ing screws holding the SCR bridge assembly
to the main transformer frame. Note insulator
placement.
17. Carefully remove the SCR bridge assembly
from the TIG 225 cutting any necessary cable
ties.
REPLACEMENT PROCEDURE
1. Carefully place the new SCR bridge assembly
in position in the TIG 225.
2. Using the 3/8" wrench install the four mounting
screws taking special care that the insulators
are in the correct positions.
USE DOW CORNING 340 HEAT SINK COM-
POUND ON ALL ALUMINUM CONNECTIONS
3. Assemble the positive lead to the right side pos-
itive heat sink.
4. Assemble the lead from the polarity switch to
the right side AC heat sink. Note: Also connect
lead #216
5. Assemble the shunt to the SCR bridge left side
negative heat sink.
6. Assemble the X2 secondary transformer lead to
the left side AC SCR heat sink. Note: Also con-
nect lead #217
7. Assemble the diode pigtail lead to the polarity
switch lead. See Figure F.10.
replace sleeving and secure with cable ties.
Position with harness and secure with cable
ties.
8. Replace any previously removed cable ties.
9. Position the internal divider panel and secure
with the screws previously removed.
10. Install the J2 plug into the control board and
position the harness in the internal divider
panel.
TROUBLESHOOTING AND REPAIR
SCR BRIDGE ASSEMBLY
Be sure to
PRECISION TIG® 225
11. Position and install the case back and secure
with the screws previously removed.
12. Install the gas hose onto the solenoid valve.
13. Tighten the input cable strain relief.
14. Assemble the case wrap-around cover.
F-43