Date: Thu, 24 Oct 2019 13:54:27 +0100
From: Chris Wilson <chris@chriswilson.tv>
To: amps@contesting.com
Subject: Re: [Amps] Non metallic paint for plywood ?
<Hello Jim,
<Could you not mount it on 4 round Teflon insulator posts internally
<threaded to divorce top and bottom mounting bolts from tying the choke
<electrically to the plywood?
<Tuesday, October 22, 2019
# Roger is probably correct. Teflon is not super robust. I have a 1 inch
diam x 12 inch long piece of solid teflon.
But I need it for plate choke material. I did find some solid Delrin
rod in my storage, 1.5 inch diam x 12 inches long...very robust.
Local plastic shop has solid delrin rod from .125 inch.... up to a
whopping 16 inch diameter...and up to 20 ft lengths !
## I could cut 4 x 1-2 inch long pieces , then tap the tops with
.25-20 or .25-28 threads. And perhaps .3125 or .375 threads on
the bottoms. I have plenty of .25-20 nylon bolts..and also .375 diam
nylon bolts.... as well as both in SS.
## Glastics would also work.
https://www.google.com/search?q=glastics&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiDq7qpvbflAhWOpp4KHX3tC1UQ_AUIEygC&biw=1455&bih=688
We used the larger glastics to support Buss bars at the telco I
worked at. Glastic also makes angle, rod, channel as well. Its just all
red HV micarta.
## Trick is to mount the insulators to bottom of choke..1st.... then
slide it ...lower it into rack onto plywood. Then slide it on plywood,
till holes in plywood line up with holes in insulators.
I only initially need 1 hole to line up, then pivot the choke, till
the other 3 holes line up...done.
## and for the several folks that emailed me stating I should wire
the choke in series with the B- lead.... it does not work ! The DC
V drop across the choke with varying plate current on
SSB results in unwanted, yo-yoing extra BIAS.... on top of, and in
addition to the normal regulated tube bias. Ok for a FM broadcast
TX..... but not a SSB linear amp. Even on CW...if idle current
is very low to begin with.... add a bunch more bias.... and the GG
triode is almost idling at zero, key clix will result. And if you
wire rvs connected diodes between B- and chassis..... and do that on
both
sides of the choke, the V drop across the choke will turn on 1 diode
on each side, re-routing choke current through the diodes.
Jim VE7RF
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