Lincoln Electric 11519 Service Manual page 67

F-21
STATIC SCR RECTIFIER ASSEMBLY TEST (continued)
FIGURE F.4
LOCATION OF LEADS X2 AND X3
NEGATIVE
CAPACITOR
BANK BUSS
BAR
6. Disconnect leads X2 and X3 (braided copper
strap) from the negative capacitor bank buss
bar using a 1/2 in. open end wrench. See
Figure F.4.
7. Separate leads X2 and X3 from the negative
capacitor bank buss bar. Be sure there is no
electrical contact.
NOTE: DO NOT DISASSEMBLE THE SCR REC-
TIFIER HEAT SINK ASSEMBLY.
8. Test for high or infinite resistance from the
anode to the cathode of SCR 1 using an analog
ohmmeter. See Figure F.5.
9. Support the door assembly.
wrench, remove the #10-24 round head screw,
lock washer, flat washer, and nut from the top
corner of the door hinge assembly, where it
attaches to the roof. Remove the support rod.
TROUBLESHOOTING AND REPAIR
LEADS X2 AND X3
CONNECTION
Using the 3/8"
Power MIG® 255XT
FIGURE F.5
SCR 1 TEST POINTS
10. Test for high or infinite resistance from the
cathode to the anode of SCR 1 by reversing
the meter leads. See Figure F.5.
a. If a high or infinite resistance is indicated
for both tests 6 and 7, the SCR 1 is not
"shorted".
b. If a low resistance is indicated in either
tests 6 or 7, the SCR is faulty. Replace the
SCR assembly.
11. Repeat steps 6 and 7 to test SCR 2.
12. Reconnect leads X2 and X3 (braided copper
strap).
13. Reconnect plugs J5 and J6.
14. If this test did not identify the problem, or to
further test the SCR, go to the Active SCR
Rectifier Assembly Test.
F-21