Lincoln Electric SVM118-A service manual Figure F.29 SCR Clamp Assembly Details 1/2 Wide Spring

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F-81 TROUBLESHOOTING & REPAIR F-81

SCR REMOVAL AND AND REPLACEMENT (continued)

FIGURE F.29 – SCR CLAMP ASSEMBLY DETAILS – 1/2” WIDE SPRING

Cap Screw

Plastic Housing

Leaf Spring

Heat Sink

SCR

Heat Sink

Plain Washer

Clamp Nut

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5)Re-inspect the SCR for proper seating.

6)Clamp the cap screws. Use the procedure for 1/4-28 cap screws or 1/4-20 bolts, depending on which you have.

Clamping procedure for 1/4-28 cap screws.

NOTE: This procedure can only be used with 1/4-28 bolts. Do not use bolts with any other type thread, or the new SCR will be damaged. Do not overtighten the cap screws. The leaf spring will apply the required clamping force to the SCR.

a.Do not turn the nuts. While holding the nuts stationary, turn the bolts only with the fol- lowing procedure.

b.Tighten first cap screw 1/4 turn.

c.Tighten second cap screw 1/2 turn.

d.Tighten first cap screw 1/2 turn.

e.Tighten second cap screw 1/2 turn.

f.Tighten first cap screw 1/4 turn. Stop. The assembly now has proper clamping force.

Clamping procedure for 1/4-20 cap screws.

NOTE: This procedure can only be used with 1/4-20 cap screws. Do not use cap screws with any other type thread, or the new SCR will be damaged. Do not overtighten the cap screws. The leaf spring will apply the required clamping force to the SCR.

a.Do not turn the nuts. While holding the nuts stationary, turn the cap screws only with the following procedure.

b.Tighten first cap screw 1/4 turn.

c.Tighten second cap screw 1/2 turn.

d.Tighten first cap screw 1/2 turn.

e.Tighten second cap screw 1/4 turn. Stop. The assembly now has the proper clamping force.

7) Perform the Active SCR Test.

SQUARE WAVE TIG 355