>
>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
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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