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8.Place the new SCR betwen the heat sinks. Be sure that the outer metal ring of the SCR is facing toward the same heat sink as the old SCR’s metal ring. Be sure that the roll pin of the heat sink engages the “hole” in the SCR. The SCR contact sur- faces must sit flat against both heat sink surfaces.
9.Clamp the SCRs to the output rectifier heat sink assembly.
10.Two different designs of leaf springs and housings have been used to clamp the SCR to the rectifier. The two different designs can be identified by the size of the leaf spring. One design uses a 1/2” wide leaf spring and the other uses a 5/8” wide spring. Follow procedure A below for 1/2” springs. Follow procedure B for 5/8” springs.
11.The different designs require different assembly and clamping procedures, depending upon the thread on the cap screws. A
A. PROCEDURE FOR THE 1/2 INCH WIDE SPRING:
1)Place a piece of sleeving around each cap screw.
2)Insert the cap screws through the leaf spring. Orient the leaf spring so that its ends are curved upward toward the cap screw heads. See Figure F.28. Pressing on the cap screw heads should produce a “rocking” motion of the spring in its housing. If the spring does NOT rock, it is installed upside down. Remove the spring and turn it over. Check for “rocking” motion.
3)Insert the cap screws and leaf spring into the plastic housing.
4)Insert clamp assembly through the heat sinks. Install the nuts. Tighten the clamp nuts equally on the cap screws until finger tight. (See Figure F.29.)
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FIGURE F.28 – 1/2” WIDE LEAF SPRING
Spring curvature exaggerated
SQUARE WAVE TIG 355
