>From what I saw it is a conventional grid driven amp. The screen resistor to
ground is to prevent negative screen current from raising the screen
voltage. The cathode resistor is obviously a mistake.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of TexasRF@aol.com
> Sent: Monday, January 30, 2006 12:10 PM
> To: Chuck_Partain@maxtor.com; dezrat1242@ispwest.com; amps@contesting.com
> Subject: Re: [Amps] cathode to ground in tetrode amp
>
>
> This schematic is a bit hard to read but it looks like the screens of the
> tubes are grounded. If this is the case, then the cathode has to be above
> ground
> for d.c. by the screen voltage value. RF is another matter and
> appropriate
> bypass capacitors will take care of that.
>
> When the cathode is above ground for d.c. rf chokes are needed to help
> isolate the rf from the power supplies (all three, grid, screen and
> plate). The
> cathode bypass C does most of this but an rf choke only helps.
>
> 73,
> Gerald K5GW
>
>
>
> In a message dated 1/30/2006 10:14:38 A.M. Central Standard Time,
> Chuck_Partain@maxtor.com writes:
>
> ya
>
>
>
> <http://www.angelfire.com/nb/ni4l/gu84b.html>
> http://www.angelfire.com/nb/ni4l/gu84b.html
>
> Look down at the ONE tube schematic.
>
> This is the only one I have seen for HF so far that's not too convoluted.
>
>
>
>
>
> -----Original Message-----
> From: Bill Turner [mailto:dezrat1242@ispwest.com]
> Sent: Monday, January 30, 2006 11:11 AM
> To: Partain, Chuck; amps@contesting.com
> Subject: Re: [Amps] cathode to ground in tetrode amp
>
>
> ORIGINAL MESSAGE:
>
> At 07:14 AM 1/30/2006, Partain, Chuck wrote:
>
>
>
> OK, getting into this more and more every day and learning. Looking at
> some
> designs on this GU-84b
> amp, I see a lot if not most of the cathodes have resistance, some a
> lot(30k) some little (.7) to ground.
> The screen grid and control grids are not grounded and have respectively
> ~350 and -150v on them.
>
> Why wouldn't it just essentially go to ground? what does the R do in
> series?
>
> thanks as always.
>
> KA1MWP
>
>
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Is there a schematic we could look at?
>
> 73, Bill W6WRT
>
>
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>
>
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