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Re: [Amps] SB-220 Replacement Tuning Cap

To: amps@contesting.com
Subject: Re: [Amps] SB-220 Replacement Tuning Cap
From: Dennis W0JX via Amps <amps@contesting.com>
Reply-to: Dennis W0JX <w0jx@yahoo.com>
Date: Fri, 12 Jun 2015 20:00:01 -0700
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Bill,
I have the replacement capacitor in my SB-220. I wouldn't call it heavy duty 
but the spacing is wider than the original SB-220 tuning capacitor. I have had 
no problems with the band switch arcing in my amplifier. However, my plate 
voltage seems to run a bit lower than some other SB-220s I have seen.

I highly recommend that you solve your arcing problem before you put in the 
replacement capacitor. File down and smooth out the plates in the original 
capacitor first using very fine crocus cloth. It may be that your parasitic 
suppressors need to be replaced. The original carbon suppressors age and change 
value over time. I replaced my suppressors with ones I found at Dayton a few 
years ago. I think they came from either an L4B or an L7. They are comprised of 
three, 120 ohm, 2 watt resistors in parallel. The coil is 3 1/2 turns of tinned 
bus wire wound around one of the resistors. My SB-220 is unconditionally stable 
on all bands, including the WARC bands.

73, Dennis W0JX

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