Modular Synth Panels

On 3/30/08, mcb, inc. put forth:
>On Sun, 30 Mar 2008, Mark wrote:
>
>  > Two grids??  Do you mean you are switching the suppression grid as
>  > well??  My plan was to switch the bias on the signal grid between two
>  > values.  Did you take any voltage measurements??
>
>The jumper alternatives on the board (one solid line, one dashed
>line) switch the suppresion grid as per Ken's modding suggestions
>on his website.  I'm *guessing* that since he changed the board
>layout, he went to the trouble of testing this first but I wanted
>a challenge anyway.

I still don't know how you switched two grids with one SPDT switch.

While Ken suggests connecting the suppression grid to a different
voltage when connecting the signal grid to a different bias voltage,
I don't think that would be necessary.  The function of the
suppressor grid is to reduce noise.  It works by  keeping electrons
emitted by the plate off the signal grid, and in order to repel
electrons it needs to be connected to a relatively negative voltage.
So it's generally connected to the cathode.  Things are more
complicated with this circuit because it uses a directly-heated
cathode, a bipolar supply, and the unmodified circuit has diodes in
series with the cathode.  Yet I don't think having it 1.2V more or
less negative is going to make a difference.  What you don't want is
a path between the signal grid and the suppression grid because that
would defeat the purpose of the suppressor grid.

>Photo is in the root directory of the files area with a 'CGS65'
>prefix.

Thanks :)  I found the picture, but couldn't figure out anything by
looking at it.