[sdiy] What is the function of this diode in the Serge DUSG?

[Guy McCusker]

I believe that this diode sinks the trigger input current (as seen by the +
terminal of the LM3900) down when the end-of-cycle is low, so that the
envelope cannot retrigger until the cycle ends.


On Sun, May 12, 2024 at 3:21 PM Paul Glass-Steel via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Hello all,
>
> I'm trying to improve my understanding of the trigger and EG logic in the
> Serge DUSG (
> https://sdiy.info/wiki/CGS_Serge_dual_universal_slope_generator). I've
> read over Tim Stinchcombe's analysis (
> https://www.timstinchcombe.co.uk/index.php?pge=vcs) many times but
> there's one component he does not touch on and I'm struggling to understand
> its roll.
>
> At the trigger input A, after the usual series of conditioning resistors
> and capacitors, there is a diode conducting the pulse into the LM3900 pin
> 13. And there is a *second* diode just below it that leads to (from?) the
> output of the end-of-cycle comparator - this is the one I'd like to
> understand.
>
> Thanks!
>
> -Paul
>
> [image: image.png]
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20240512/81c78ced/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 223649 bytes
Desc: not available
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20240512/81c78ced/attachment.png>