[AMRadio] 813 Triode Connected Bias question.


ARS W5OMR ars.w5omr at gmail.com
Fri Mar 20 21:47:55 EDT 2015


Hook up  a 9v battery,  reversed, in the center tap of the filament
transformer secondary and put some voltage to it.  If that's not enough,
add another until you have too much voltage, then wire a pot across the
batteries.

I did this without the pot on a pair of 810's... I think I wound up with 5
or 6 9v batteries strung together for 45 or 50v of bias.
 On Mar 20, 2015 5:16 PM, "Paul Baldock" <paul at paulbaldock.com> wrote:

> I am building a 2x813 pp triode connected modulator. This means the screen
> grid and control grid are connected together for each tube.
>
> I haven't found any characteristic curves for the 813 in this configuration
>
> On a sample of one, with 0 volts on the grid I measure about 40mA Idle
> Current (single tube). 40mA means about 100W per tube. Does anybody have a
> guess at what negative bias I would need to reduce this to around 20mA?
>
> Thanks
>
> - Paul  KW7Y
>
>
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