Lincoln Electric SVM151-A service manual Replacement, Refer to Figure F.14

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F-56	F-56
	TROUBLESHOOTING & REPAIR

CHOPPER PC BOARD REMOVAL AND REPLACEMENT (CONTINUED)

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3.Perform the Case Cover Removal proce- dure.

4.Perform the Power Capacitor Discharge procedure.

5.Carefully turn the machine onto its side.

6.Using the 3/8" wrench, remove the four screws holding the tunnel assembly to the machine base. Support the tunnel assem- bly, then carefully turn the machine back upright.

7.With the slot head screw driver, carefully raise the tunnel assembly unit about one inch and block it with the piece of wood. This will allow access to the bottom allen head screws on the Chopper PC Board. Peel away the adhesive-backed rubber stripping if present. Use care – the strip- ping may tear.

8.Disconnect the plug harness connection above the Chopper PC Board. Slip the wires out of the cord clip.

9.Using the 7/16" wrench, loosen the bolt at the positive capacitor terminal. Then remove the two nuts, lock washers and flat washers holding the positive strap to the Chopper PC Board. Hold the screw heads behind the board with your finger to remove the nuts. Note the placement of the reverse diode lead on the bottom bolt. Note the fastener order for reassembly: flat washer, lock washer, nut.

10.With the 7/16" wrench, remove the two hex-head bolts, lock washers, and flat washers holding the Chopper PC Board to the heat sink. Catch the copper stand-offs behind the board.

11.Using the 3/16" allen head wrench, remove the two allen-head screws and lock wash- ers holding the Chopper PC Board to the heat sink.

12.Swing the positive capacitor strap out of the way and remove the Chopper PC Board.

REPLACEMENT

Refer to Figure F.14.

1.Make sure the mating surfaces between the copper and the heat sink are clean, dry, and free of grease.

2.Apply a thin coating of electrical thermal joint compound (Penetrox A-13) to the mat- ing surfaces between the copper and the aluminum heat sink.

3.Using the torque wrench and 3/16" allen head socket, install the two allen-head screws and lock washers that hold the Chopper PC Board to the heat sink. Tighten the screws finger tight, then to between 24 and 28 in-lbs., then again to between 40 and 48 in-lbs.

4.Using the 7/16" socket and torque wrench, install the two bolts, lock washers, and flat washers that hold the Chopper PC Board to the heat sink. Note the two spacers required. Tighten the bolts finger tight, then to between 50 and 60 in-lbs.

5.Put the positive strap (+) in position and the proper heavy lead. Using the 7/16" wrench, tighten the bolt at the positive capacitor ter- minal to between 50 and 60 in-lbs. Then put the flat washers, lock washers and nuts on the board side of the strap with the reverse diode lead on the bottom connec- tion. Tighten to between 50 and 60 in-lbs.

6.Remove the wooden blocking and carefully lower the tunnel assembly onto the machine base. Support the tunnel assem- bly and turn the machine onto its side.

7.With the 3/8" wrench, install the four screws that hold the tunnel assembly to the machine base. Turn the machine back upright.

8.Connect the harness plug above the Chopper PC board. Slip the wires into the cord clip.

See the procedures following for removal and replacement of the diode module. When proce- dures are complete, perform the Case Cover Assembly Replacement procedure.

MULTI-WELD 350