Micarta insulator material?
I posted recently that I have ordered the tank components for my Henry 2K
Classic X and they are in shipping to my address at this time. My question is
this: I disassembled the band switch with its associated band plate tuning
capacitors, which are progressively added in as you lower the band frequency.
These are switched in by the band switch assembly adding capacitors thus
capacitance as you lower the frequency selected. The plate is dipped with the
roller inductor on this amplifier, not a variable capacitor.
Having said that, I noticed that the insulator material (named Micarta by Henry
- black material with what looks like fibers running through it) on the band
switch is discolored on the end nearest the front of the amp. So is the
associated band switch mounting hardware (all metal is at ground potential)
attached to this insulator. This appears to be a place where arcing occurs.
My immediate solution was to reverse the insulator in all the hardware
mountings so the discolored portion was now at the rear of the amplifier
instead of near the front.
I tuned and loaded the amp into my 50 ohm PalStar dummy load and as I
approached the top end of the output I heard some distinct frying happening
again. I lower input power to the amp and this frying sound diminished and
finally quit just as I was unkeying the driver stage.
Opening the amplifier up I see the fresh end of the insulator material is now
also slightly discolored and the metal mount has a discolored mark on it as
well. There was an arc between the lower portion of the last doorknob
capacitors (two in parallel) to the mount.
Have any of you other Henry owners experienced this problem in the band switch
area? If so can you advise any solutions you have explored and their outcomes?
It looks to me that the mount itself has a bit of a sharp corner on it, the
metal mounting flange that attaches to the insulator material, and from that
sharp point it is arcing across the insulating material to the last contact on
the band switch which is connected to the lower portion of two 75pf caps in
parallel for 80 meters.
By the way this happened on 40 meters so the last two caps were not even
selected by the bandswitch.
My proposed solution is to cut off the upper portion of the metal mount in this
area so there is a larger distance between ground and the bottom of those two
caps, that way there is not an easy opportunity to make the one quarter inch(?
approx value I did not measure it) jump that the contact and the mount is
providing right now.
OK solutions other than that proposed? Do not want to fry a new band switch
assembly right away!
I also have a new roller inductor arriving with these parts and want to
refurbish the old one which itself has some frying issues of its own. Will
post on that later on.
Thank you
Gene Bigham
KB0GU
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