Re: [Amps] Alpha 77Dx -Adding Grounded Grid Filament Choke

[R.Measures <r@somis.org>]

On Mar 4, 2005, at 6:30 AM, Paul Christensen wrote:

> Whoops - my mistake.  The 77Dx's 8877 does not tie the cathode and 
> filament
> together.  One side of the filament is grounded.  Would it still be
> advisable to add the common-mode filament choke anyway?

Not if you have a free supply of 8877s.
-  I would add a bifilar RFC, unground the filament/heater winding, and 
wire the cathodes to one side of the heater.
>
> -Paul, W9AC
>
> ----- Original Message -----
> From: "Paul Christensen" <w9ac@arrl.net>
> To: "AMPS" <amps@contesting.com>
> Sent: Friday, March 04, 2005 9:22 AM
> Subject: [Amps] Alpha 77Dx -Adding Grounded Grid Filament Choke
>
>
>> Last week's discussion of GG filament chokes got me thinking about
> modifying
>> my Alpha 77Dx which I believe, ties one side of the filament to the
> cathode.
>> I would like to cut this tie and user a R.F. Parts Co. FILRFC-30 
>> filament
>> choke.
>>
>> http://www.rfparts.com/choke.html
>>
>> I am assuming that a combination of HV-rated 0.01 uF and 0.1 uF disc 
>> caps
>> could be used to bypass each side of the filament tube terminals to
> ground.
>> Anything else I should consider before doing this?  Thanks!
>>
>> -Paul, W9AC
>>
>>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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