Lincoln Electric IDEALARC DC-655 Service Manual page 79

F-37
ANODE
CATHODE
REMOVE
INSULATING
PAINT
6. If a high or infinite resistance is indicated for
both steps #4 and #5, SCR1 is not shorted.
7. If a low resistance is indicated in either steps
#4 or #5, there is a shorted SCR in the out-
put rectifier bridge. Repeat steps #4 and #5
for each of the six SCRs. It may be neces-
sary to disconnect the transformer sec-
ondary leads from the rectifier assembly to
isolate the defective SCR(s). See the Wiring
Diagram.
TROUBLESHOOTING & REPAIR
STATIC SCR TEST (continued)
FIGURE F.15 – HEAT SINK TEST POINTS
IDEALARC DC-655
8. Replace plug J9 into the thermal fan/snub-
ber board and plug J5 into the firing board.
NOTE: To further check the SCRs' functions use
an SCR tester and proceed to the Active SCR
Test.
F-37