[BC] Harris RF Contactor Maintenance

[Grady Moates]

    It has been my experience that a defect in the design of
the Harris contactor causes it to fail in extremely cold
weather.

    An examination of the mechanism when moving shows that
the microswitches were installed improperly.  When the
"slide" moves from end to end, there is an over-travel that
causes the microswitch lever to actually bend a substantial
amount.  There is no way to prevent this the way it's built,
it just happens.  It works OK in warm weather, when the metal
in the microswitch lever has a reasonable amount of springiness,
but when it gets extremely cold, the lever metal just deforms,
and then the switches don't close at the proper moments in the
movement of the slide.

    If the microswitches had been turned 90 degrees, so that
the slide could simply move the levers to the side, then
the rollers would roll along the cam surfaces on the side of
the slide, allowing the slide to over-travel without any
bending of the microswitch levers.

    The Harris contactor was a great idea. . . an RF contactor
that doesn't SLAM from one position to another, fatiguing
everything in the phasor, cracking insulators and causing
j-plugs to slip out, but the realization of the idea just
doesn't work well below about 20 degrees F.  Once the
little levers are bent in the cold weather, they don't
come back to normal when they warm up, and needlenose
adjustment is necessary.

Grady