Lincoln Electric SVM151-A service manual 25-27 300-324, Refer to Figure F.11

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F-47	F-47
	TROUBLESHOOTING & REPAIR

INPUT DIODE REMOVAL AND REPLACEMENT (CONTINUED)

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10.Disconnect thermostat leads #306 and #307.

11.Carefully remove the input diode assembly.

12.Using the 11⁄4" wrench, loosen the appropri- ate diode and remove the diode that is to be replaced.

13.Clean the area on the heat sink around the diode mounting surface using a putty knife or similar tool. DO NOT SCRATCH THE DIODE MOUNTING SURFACE.

14.Polish the heat sink’s mounting surface to provide a bright, clean surface where the diode seats on the heat sink. Wipe the sur- face clean with a lint-free cloth or paper towel.

15.Inspect the mounting surfaces of each new diode. Remove all burrs and wipe clean. Do not use steel wool or any abrasive cleanser on the diode mounting surface.

16.Apply a thin (0.003" to 0.007") uniform layer of Penetrox A13 joint compound to the heat sink mounting surface.

17.Do not apply compound to the diode stud or mounting threads.

18.Apply two drops of Loctite 271 to the diode stud threads before tightening.

NOTE: The diode threads must be clean and free of defects so that it can be finger tightened before applying torque. A “slip” type torque wrench must be used to tighten the diode.

19.Tighten the diode to the specifications in the following table.

DIODE
STUD	FOOT-POUNDS	INCH-POUNDS
SIZE
3/4 - 16	25-27	300-324

REPLACEMENT PROCEDURE

Refer to Figure F.11.

1.Set the input diode assembly into the machine base. Connect the heat sink to the input terminal strap with the 1/2" bolt, wash- ers, and nut. Note order – see removal pro- cedures.

2.Install the heat sink to the choke, using the 3/8" bolt and nylon insulators, along with the mylar insulation sheet. The mylar sheet fits between the nylon insulators.

3.Connect thermostat leads #306 and #307. See the Wiring Diagram.

4.Perform the Input Contactor Replace- ment procedure. Be sure to connect the input diode pig-tails to the contactor strap at the contactor rear terminal.

5.Replace any cable ties cut at disassembly.

6.Perform the Case Front Assembly Replacement procedure.

7.Perform the Case Cover Assembly Replacement procedure.

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MULTI-WELD 350