[AMRadio] 813 Triode Connected Bias question.


Larry Szendrei ne1s at securespeed.us
Sat Mar 21 10:03:23 EDT 2015


On 3/21/15 5:54 AM, Rob Atkinson wrote:
> http://www.pentalabs.com/pdfs/pl813.pdf
>
>
> Rob
> K5UJ
>
> On Fri, Mar 20, 2015 at 9:37 PM, Paul Baldock <paul at paulbaldock.com> wrote:
>> I'm think it will be just a few volts for the 813 triode configuration.
>>
>> I could figure the voltage by putting a 1K pot in the center tap and
>> adjusting it for 20mA, (this would allow 20V max). Then when I know the
>> voltage, replace the pot with a zener or string of diodes with parallel
>> electrolytic.
>>
>> - Paul
>
Appreciate the link to that data sheet, Rob. Saved for future reference.

However, there is no data for use in the triode class B connection, and 
that is what Paul is looking for.

In the absence of that data I think his suggested approach of putting a 
pot in the cathode lead (center tap of fil. xfmr) to find the correct 
operating point and then replace with a Zener (or forward-biased diode 
string) of the correct value is a good one, and the one I would probably 
use.

73,
-Larry/NE1S


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