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Re: [Amps] ALPHA 77 RF POWER CAPACITORS

To: "R.Measures" <r@somis.org>
Subject: Re: [Amps] ALPHA 77 RF POWER CAPACITORS
From: Frank Goenninger <frank_goenninger@t-online.de>
Reply-to: frank_goenninger@t-online.de
Date: Thu, 08 Jan 2004 14:58:00 +0100
List-post: <mailto:amps@contesting.com>
Replace each "strange" char with a "0". Then you get "500 pF". 
But I'm sure you knew already ;-)

Another one of that character encoding sh.. !

73, Frank


On Thu, 2004-01-08 at 13:33, R.Measures wrote:
> **  How much C is:  5ÿÿpF?
> 
> >
> >Gentlemen,
> >
> >Not too long ago in this reflector a discussion was had about certain RF 
> >power capacitors being prone to failure in the ALPHA 77Sx amplifier, more 
> >specifically thus:
> >
> >  :: "The 16ÿm doorknob padder should have a higher ampacity."
> >       From what I see of the schematic, C4ÿ: 5ÿÿpF/5KV is type 85ÿs.
> >
> >  :: "The two 8ÿm doorknob padders are prone to failure."
> >       They are listed as C41,42: 1ÿÿpF/5KV, type 858s.
> >
> >  :: "The Plate Blockers are too light."
> >       They are listed as C2ÿ,21: 1,ÿÿÿpF/5KV, type 858s.
> >
> >  :: "The Plate Choke RF bypass capacitor is prone to failure."
> >       It is listed as C35, 1,ÿÿÿpF/5KV, type 858s.
> >
> >  Observed: The additional bypass caps on the plate circuit are
> >            2,ÿÿÿpF/6KV disk ceramics. Two of these parallel a
> >            15uH, 1 amp RF choke, L9.
> >- - - - - - - - - - - - - - - - - - - - - - - - - 
> >Questions:
> >    1. What are your recommendations for upgrading the reliability
> >       of the capacitors above? Several issues arise: E and I ratings,
> >       and the best type: HT50, HT58, HT57...?
> >
> >    2. If the amplifier is capable of 2.ÿ plate amperes on the 'Sx 
> >       version with two 3CX15ÿÿA7 finals, then is not L9, at 1.ÿ amp
> >       prone to failure from over heating?
> >
> >    3. The capacitors paralleling L9, the disk ceramics, are rated
> >       at 6KV. However, should their value of capacitance increase?
> >
> >    4. The 16ÿm and 8ÿm padders seem kind of light in capacitance for 
> >       the new output impedance of two 8877's. Should not their value
> >       increase dramatically to affect the tank's Q?
> >(Reference: HV:3,9ÿÿVDC)
> >(Vac.Var. changing to 7~1,ÿÿÿpF/7.5KV)
> >Thank you for your opinions.
> >
> >Hal Mandel
> >KA1XO
> >_______________________________________________
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> >Amps@contesting.com
> >http://lists.contesting.com/mailman/listinfo/amps
> >
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