Lincoln Electric SVM123-A service manual SCR Output Bridge Removal

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F-50 TROUBLESHOOTING & REPAIR F-50

SCR OUTPUT BRIDGE REPLACEMENT

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SCR OUTPUT BRIDGE

REMOVAL

1.Remove input power to machine.

2.Using a 5/16 (8mm) nut driver or flat head screw driver, remove 20 screws (ten per side) to remove case sides and 2 screws to remove top.

3.Using a 5/16 (8mm) nut driver or flat head screw driver, remove 6 screws, then lower the front control panel.

4.Remove the J4 gate lead Molex plug from firing board, and feed the plug down through the hole in bot- tom of the PC board compartment.

5.Using a 9/16” socket and open-end wrench, remove the two bolts and nuts holding the shunt assembly to the two positive buss leads con- nected to the SCR bridge. See Figure F.22.

6.Using a 5/16” socket remove the screw and small reed switch lead (#210) from the left, top rear SCR heat sink.

NOTE: It may be necessary to move or remove the output choke to gain access to the bottom anode leads. For access to the bottom middle screw, nut, and associated washers, a long handled flat ratchet is recommended.

7.Identify and label the six trans- former secondary (heavy alu- minum) leads that connect to the anodes of the SCR heat sink assemblies. Using a 1/2” socket and open-end wrench, remove the secondary leads (see Figure F.22).

8.Support the SCR bridge assembly with a lift hook or rope.

9.Using a 3/8” socket wrench, remove the two screws (one on each side) holding the SCR assem- bly rails to the front panel assem- bly.

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FIGURE F.22 - Preparation For SCR Output Bridge Removal

IDEALARC DC-1000