Leads, Troubleshooting & repair, Static scr test – Lincoln Electric MULTI-SOURCE SVM155-A User Manual
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F-23
F-23
STATIC SCR TEST
(Continued)
TROUBLESHOOTING & REPAIR
MULTI-SOURCE
Leads
4. Using the 9/16” wrench, remove the two
positive output leads connecting the out-
put bridge to the shunt. See Figure F.8.
This will partially electrically isolate the
SCR Bridge for testing purposes. See
Wiring Diagram.
5. Remove the red insulating paint from heat
sink test points. See Figure F.9.
NOTE: DO NOT DISASSEMBLE THE HEAT
SINKS.
6. Using an analog ohmmeter, test the resis-
tance from anode to cathode of SCR 1.
Reverse the meter leads and check from
cathode to anode of SCR 1 (R x 1000
scale). See Figure F.9.
a.
If a low resistance is indicated in either
direction, one of the SCRs may be
faulty. Further isolation will be neces-
sary to determine which SCR is faulty.
This isolation can be accomplished by
disconnecting the transformer sec-
ondary lead from the SCR under test.
See the Wiring Diagram.
FIGURE F.8. Shunt and Lead Connections