[ARC5] BC-375 Re-Tube Project- Scratch Three

[Fuqua, Bill L]

  I suspect that it is not the thermal noise that gets the power oscillators started up but
the electron shot noise.
73
Bill wa4lav

________________________________________
From: Fuqua, Bill L
Sent: Tuesday, November 19, 2013 1:44 AM
To: Geoff; kgordon2006 at frontier.com; David Stinson; ARC-5 List
Subject: RE: [ARC5] BC-375 Re-Tube Project- Scratch Three

  what about a 812 or 812A. They are medium mu and probably sufficient plate dissipation.
Power oscillators usually use medium mu triodes so that there is sufficient plate current at low bias or zero bias to start up
oscillation.
  An  example is one used in a self-oscillation plasma generator that I recently got a tube from.
It had a 3-1000H. I have seen other power oscillators using 812 tubes as well.

73
Bill wa4lav

________________________________________
From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on behalf of Geoff [geoffrey at jeremy.mv.com]
Sent: Monday, November 18, 2013 4:13 PM
To: kgordon2006 at frontier.com; David Stinson; ARC-5 List
Subject: Re: [ARC5] BC-375 Re-Tube Project- Scratch Three

And then there is also the 809, T-40 and T-40Z, all of which are fairly
available.

Carl


----- Original Message -----
From: "Geoff" <geoffrey at jeremy.mv.com>
To: <kgordon2006 at frontier.com>; "David Stinson" <arc5 at ix.netcom.com>; "ARC-5
List" <arc5 at mailman.qth.net>
Sent: Monday, November 18, 2013 4:02 PM
Subject: Re: [ARC5] BC-375 Re-Tube Project- Scratch Three


> What about an 811 or 812, A or non A?
>
> Carl
>
>
> ----- Original Message -----
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> To: "David Stinson" <arc5 at ix.netcom.com>; "ARC-5 List"
> <arc5 at mailman.qth.net>
> Sent: Monday, November 18, 2013 11:47 AM
> Subject: Re: [ARC5] BC-375 Re-Tube Project- Scratch Three
>
>
>> On 18 Nov 2013 at 3:10, David Stinson wrote:
>>
>>> Three candidate tubes for the
>>> "Cheap Tubes for the BC-375" project have disappointed.
>>> 1625, 837 and 7984 will not "hold up" in this service.
>>> Once the screen voltages are dropped to spec,
>>> the tubes lack the gain to oscillate reliably, even
>>> with heavy "gimmick" cap coupling between grid
>>> and plate in the OSC stage.
>>
>> David: Have you yet tried connecting the screen to the GRID (G1). As I
>> said
>> earlier, this results in a HIGH-MU triode, which SHOULD work much better
>> as an oscillator.
>>
>> Kenneth G. Gordon W7EKB
>>
>> "Courage is being scared to death but saddling up anyway."--- John
>> Wayne
>>
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