[Amps] insulation

[W0UN -- John Brosnahan]

>
>The opposite example is that I once used Delrin for the PA tuning shaft in 
>a little 6522 2m transmitter. The capacitor rotor was *supposed* to be at 
>RF ground, and that TX couldn't have been putting out more than 25W, tops 
>- but the Delrin melted in seconds. Wrong place, I guess.

Hi, Ian--

Are you SURE that the material was Delrin?  Sure sounds like NYLON
to me.  I have been using Delrin as the form for the plate RF choke on
my 3CPX5000A7 amps at 49 MHz.   These run 50-100 KW pulse and
2 or 3 KW average and often transmit for WEEKS at a time--in some
cases for YEARS.  I have NEVER had a failure of a Delrin RF choke
or ANY hint of any heating.  I have been building these amps--at
least 100 in the field--for the past 20 years and not one single problem
with Delrin as the RF choke form.

So I am quite surprised with your results--to the point of believing
that it was probably NOT Delrin.

73--John   W0UN



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