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[AMPS] FL-2100B Plate Choke rewind?

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Subject: [AMPS] FL-2100B Plate Choke rewind?
From: (Rich Measures)
Date: Wed, 24 Feb 1999 09:23:41 -0800

>Hi all,
>The plate choke in my recently acquired FL-2100B has a burnt midsection in
>the step-wound plate choke - it and the blocking cap and one 2R2 plate
>resistor arced when I was trying to see if it would tune up on 18mHz in the
>21 mHz position. It emitted a loud BANG, a bright flash blue/white, (and a
>small stream of smoke from the resistor).
>I guess I need to rewind the choke - Is the wire size/type critical? 

?  not as long as it will carry the current and RF-v gradient per turn.  
In anode hv-rfc service, #30 will easily carry 500mA.  

>Is the shape of the winding (?step  wound?) critical? 

?  Step-winding / gaps between sections sounds like it might be a good 
idea.  I conducted a comparison experiment and found that it does 
essentially nothing to change the resonance problem.   I would go with a 
single-later solenoid choke, close wound with modern silicone-varnish 
(high-temp) wire from an electric motor rewinding shop, varnish winding 
with gloss-urethane, let dry, install in amp, measure resonances with 
dipmeter, and remove turns as needed to move resonances >5% from 
operating frequencies.  // a section on hv-rfc construction is in 
'Amplifiers', which is on my Web site.  

-  cheers, Bob


R. L. Measures, 805-386-3734, AG6K,  

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