[Amps] Henry 2K Classic X

[R.Measures]

On Mar 15, 2005, at 2:43 PM, Gene Bigham wrote:

> 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.

IMO, the solution is to discourage regeneration at approx. 95MHz by 
decreasing the Q of the VHF suppressors - which in turn lowers anode-Rp 
and decreases VHF amplification.   A high VHF-Q suppressor makes about 
as much sense as a shock-absorber with almost no dampening.  Henry 
Radio Co. has a Long tradition of using high VHF-Q "parasitic 
suppressors" . . . and not using their noggins.

Gene -- If you need some Micarta, I have 0.25" thick msterial.  The 
color is red.

> 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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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org