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[AMPS] Filament Choke Question (RE: Handbook example)

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Subject: [AMPS] Filament Choke Question (RE: Handbook example)
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Date: Sat, 20 Feb 1999 15:53:10 -0500

On Sat, 20 Feb 1999 11:04:46 -0600 Jon Ogden <> writes:
>Was looking at my 89 handbook at some of the amplifier designs to look 
>what folks were using for filament chokes.  Starting on page 30-50, 
>is a design for an 8877 amp.  In looking at the schematic, the guy 
>NO filament choke.  The two filament lines are both bypasssed to 
>by .01 uF caps.  From what I can tell the filaments are on pins 1 & 5 
>the tube and the schematic says that pins 2,3,4,6, & 7 are the cathode 
>input.  Yes, it's grounded grid.
>Is the 8877 set up this way so that the filament pins are isolated 
>the cathode?  Is that why he's able to get away with it?  I'm ignorant 
>how the 8877 is set up.

The 8877 is indirectly heated as is the 8874, 3CX800, YC-156 and others.
A small filament choke is advantageous in order to assure full isolation.
Ameritron uses one as did Dentron which may account in part for their
excellent stability without voodoo .

73  Carl  KM1H

>Just curious.
>Jon Ogden
>    <--- CHECK IT OUT!  It's been 
>"A life lived in fear is a life half lived."
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