Lincoln Electric PRECISION TIG 275 SVM162-B - Manual (Page 82)

F-36 F-36
PRECISION TIG 275
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TROUBLESHOOTING & REPAIR
ACTIVE SCR TEST (continued)
TEST PROCEDURE
1. Remove main supply power to the PRECI-
SION TIG 275 machine.
2. Locate and remove plug J4 from the control
board. See Figure F.7.
3. Perform the following test for all four SCRs.
See
Figure F.8
.
4. Construct the circuit outline in
Figure F.8.
One 6V lantern battery can be used. Resistor
values are +\- 10%. The voltmeter scale
should be approximately 0-5 or 0-10 volts.
5. Battery Test - Check the battery by shorting
leads (A) and (C) and then close switch SW-
1. Replace the battery if voltage is less than
4.5 volts.
Plug
J4
G3909
Figure F.7 - Plug J4 Location