Elecraft KPA500 Kit Assembly Manual - Manual (Page 36)

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Orient the transformer as shown in Figure 51, taking care not to dislodge the bumpers. Add the second
rubber disk and metal disk as shown. Orient the metal disk so the center depression goes down into the center of
the transformer. Add the Belleville washer and secure the assembly with the Nylock nut. Tighten the nut
enough to hold the hardware in place (you will tighten the nut further later).
IMPORTANT: The Belleville washer is not a flat washer. It is slightly conical shaped
and acts as a spring. When properly installed the area around the center hole under the nut
will be slightly higher than the outer edges. The nut bearing down on the washer will tend
to flatten it, helping to hold the transformer securely. The conical shape is very subtle. To
determine the correct orientation, place the washer on a hard flat surface and press on the
edge. If it wobbles slightly, the washer is upside down. If pressing the edge causes no
wobble, it is right side up. Be sure to install the washer right side up on the top metal disk.
Figure 51. Mounting the Power Transformer.