The 813 is well underated. Most will hi-pot with plenty of overhead for 3KV
on AM.
The 572B is simply a 811 with a graphite anode and runs fine at 2500V in
lots of commercial ham amps.
Carl
KM1H
----- Original Message -----
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
To: <dezrat1242@yahoo.com>; <amps@contesting.com>
Sent: Monday, July 27, 2009 4:18 PM
Subject: Re: [Amps] 4x813`s in GG
>A good example of running tubes over the published Plate voltage limits is
>the E.F. Johnson Viking 500 plate modulated AM transmitter.
> The final tube 4-400 and the modulator tubes 811A's were run with 2kV on
> the plates.
>
> 73
> Bill wa4lav
> ________________________________________
> From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf
> Of Bill, W6WRT [dezrat1242@yahoo.com]
> Sent: Monday, July 27, 2009 2:30 PM
> To: amps@contesting.com
> Subject: Re: [Amps] 4x813`s in GG
>
> ORIGINAL MESSAGE:
>
> On Mon, 27 Jul 2009 18:38:35 +0100, jonathan white
> <jonathan.white20@btinternet.com> wrote:
>
>> Anode volts will be around 2,800 volts
>
> REPLY:
>
> You probably can get away with it, but the manufacturer's data sheet says
> 2500
> VDC is the max allowed. There probably is a little cushion there but I
> wouldn't
> push it too far.
>
> 73, Bill W6WRT
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