I recently bought a used Henry 3K Premier. Something arcs when I tune it
up only on 12M and only with the HV switch in the SSB position. I
removed the cover to take a look and found that the rotary inductor was
exactly one turn from minimum. This placed the rotary contact in close
proximity to the termination at the end of the winding. I tried running
the amp briefly with the cover removed to visually confirm that this was
where it was arcing. Unfortunately, removing the cover affected the
tuning, and when retuned there was no arcing but neither was the rotary
contact in proximity to the end contact anymore.
Unless someone has a better suggestion, I'm going to apply an insulating
coating to the termination area at the end of the inductor to see if
that fixes the problem. I can use either "Q Dope" or "Corona Dope". "Q
Dope" is intended for RF circuits and shouldn't have any effect on the
inductance or Q of the circuit, but may not have sufficient insulating
capabilities. "Corona Dope" is intended for high voltage circuitry in
television receivers, but might not be as good a choice for an RF
circuit. My gut feeling is that I should use the "Corona Dope" because
it will be applied to less than one inch of the inductor and therefore
should have a minimal effect on the inductance or Q. On the other hand,
the increase in breakdown voltage required to fix the problem may not be
very much and the "Q Dope" might be adequate. Opinions, anyone? Thanks!
73,
John, K9MM
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