[Amps] Non metallic paint for plywood ?

[Jim Thomson]

Date: Thu, 24 Oct 2019 13:54:27 +0100
From: Chris Wilson <chris at chriswilson.tv>
To: amps at 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