Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 137

F-85
OUTPUT RECTIFIER REMOVAL AND REPLACEMENT (continued)
PROCEDURE
1. Remove input power to the machine.
2. With the 5/16" nutdriver, remove the case top
and sides.
3. Perform the Input Power Factor Capacitor
Voltage Check.
For Steps 4-27, refer to Figure F.26.
4. Remove plug J1 from the power PC board.
5. With the 1/2" wrench, remove the choke lead
from the negative plate.
6. With the 1/2" wrench, remove the X1 lead from
SCR1 - SCR4 junction. Note lead placement
for reassembly: X1 is sandwiched between the
two leads from the output rectifier bridge.
7. With the 1/2" wrench, remove the lead at the
SCR2 - SCR3 junction leading to the polarity
switch (S1). Note lead placement for reassem-
bly.
8. With the 1/2" wrench, remove the lead from the
positive plate leading to the polarity switch (S1).
9. With the 7/16" wrench, remove the small lead
from the negative plate leading to CR3 relay.
10. With the 7/16" wrench, remove D1, D2 and the
copper strap lead assembly from the insulated
stud on the negative plate.
11. Remove leads #215 and #264 from the R7
resistor.
12. Remove leads #213 and #214/214A from the
background rectifier. Separate leads #214 and
#214A and pull them through. Cut any neces-
sary cable ties.
13. Remove (cut or unsolder) lead #212 from the
R3 resistor.
14. Remove leads #210 and #211 from plug J1
(Located at power board.
Diagram). Use a molex pin extractor. Note
lead placement for reassembly.
TROUBLESHOOTING AND REPAIR
See Wiring
SQUARE WAVE TIG 355
15. With the 7/16" wrench, remove the four nuts,
lock washers, and two flat washers mounting
the rectifier assembly to the main transformer
iron.
NOTE: The two flat washers are located on
the right hand mounting screws.
16. Carefully remove the rectifier, snubber, and tor-
riod assembly.
17. Reassembly: carefully mount the rectifier,
snubber, and torriod assembly onto the main
transformer iron. With the 7/16" wrench, fasten
the assembly down with the flat washers, lock
washers, and nuts. Note that the two flat wash-
ers are located on the right hand mounting
screws.
18. Attach lead #212 to the R3 resistor. (Splice or
solder the connection.)
19. Route leads #213 and #214/214A and attach
them to the background rectifier. Replace any
necessary cable ties.
20. Attach leads #215 and #264 to the R7 resistor.
21. With the 7/16" wrench, attach D1, D2 and the
copper strap lead assembly to the insulated
stud on the negative plate. Attach the small
lead from the CR3 relay to the negative plate.
22. With the 1/2" wrench, attach the lead from the
polarity switch (S1) to the positive plate.
23. With the 1/2" wrench, attach the lead from the
polarity switch (S1) at the SCR2 - SCR3 junc-
tion.
24. With the 1/2" wrench, attach the X1 lead to the
SCR1 - SCR4 junction.
between the two leads from the output rectifier
bridge.
25. With the 1/2" wrench, attach the choke lead to
the negative plate.
26. Attach plug J1 to the power PC board.
27. With the 5/16" nutdriver, install the case top
and sides.
F-85
X1 is sandwiched