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PRECISION TIG 185
TROUBLESHOOTING & REPAIR
F-26 F-26
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TEST PROCEDURE
1. Remove main supply power to the
TIG 185 machine.
2. Locate and remove plug J2 from the
control board. See Figure F.3.
3. Perform test procedure as outlined in
Figure F.5. Repeat test for all four
SCRs. See Figure F.6.
4. Construct the circuit outlined in Figure
F.5. One 6V lantern battery can be
used. Resistor values are ±10%. The
voltmeter scale should be low,
approximately 0-5 or 0-10 volts.
5. Battery
T
est - Check the battery by
shorting leads (A) and (C) and then
close switch SW-1. Re-place battery if
voltage is less than 4.5 volts.
ACTIVE SCR TEST (continued)
FIGURE F.5 ACTIVE SCR TEST SETUP
SW1
R2
SW2
R1
A
G
C
V
SCR
under
test
R1= 4 ohms /10 watts
R2= 3 ohms/ 10 watts
6volt
Lantern
Battery
To test SCRs construct the circuit outlined above.
Resistor values are plus or minus ten percent. The
voltmeter scale should be low, approximately 0-5 or
0-10 volts DC.