Lincoln Electric IDEALARC DC-1000 Service Manual page 91

F-57
SCR OUTPUT BRIDGE REPLACEMENT (continued)
SCR HEAT SINK INSTALLATION
NOTE: Upon reassembly, apply a thin layer of
Lincoln E1868 (Dow Corning #340) heat
sink compound to all bolted electrical con-
nections on the aluminum heat sinks,
including positive buss bar.
1. Slide a new SCR assembly onto the mounting
studs.
2. Carefully attach the positive buss bar onto the
heat sink which had been removed. If it had
been necessary to remove the buss bar,
replace it at this time.
3. Align snubber assembly in position on SCR out-
put bridge assembly.
4. Using a 9/16" wrench, secure the SCR output
bridge and snubber assemblies with two nuts,
flat washers, and lock washers.
5. Using a 5/16 (8mm) nut driver or flat head
screw driver, attach snubber assembly ground
wire with screws previously removed.
TROUBLESHOOTING AND REPAIR
IDEALARC
SCR OUTPUT BRIDGE INSTALLATION
NOTE: Upon reassembly, apply a thin layer of
Lincoln E1868 (Dow Corning #340) heat
sink compound to all bolted electrical con-
nections on the aluminum heat sinks.
1. Support the SCR bridge assembly with a lift
hook or rope.
2. Clear all leads and carefully position the SCR
bridge assembly in place.
3. Place insulators between SCR bridge assembly
and the output rectifier mounting bracket. See
Figure F.23. Check for electrical isolation with
an analog ohmmeter. Minimum acceptable
resistance to ground is 500,000 ohms.
4. With the 5/16" socket wrench, attach bottom six
screws securing the front panel assembly to the
base. Carefully push the front panel rearward
into position.
5. Attach resistor R2 to the unit using a 7/16"
wrench Secure leads #217 and #222 to resistor
R2.
6. Using a 1/2" socket wrench, attach the four
screws (2 on each side) holding the transformer
side panels and SCR assembly rails to the main
transformer.
® DC-1000
F-57