[sdiy] Adding reset clock to CD4520

[René Schmitz]

Hi Denshi,

The pin number of the 4520 is wrong, the reset pins are 7 and 15. If 
you've wired it like in the diagram then two outputs are connected.

What you describe here is sometimes caused by the capacitor not being 
able to discharge before the next pulse arrives.
Once the cap is charged up it can not produce another pulse until it has 
discharged through the 68k/33k combination.
The base current can only go in one direction leaving the cap charged if 
there was no other path to GND.
If the cap is big then it can take a long time.
I've had similar failures in these pulse forming circuits when there is 
no discharge path.
Sometimes I'm adding a diode between B and E to provide a fast discharge 
path. Cathode would go to the base of the transistor.



Best,
  René



On 22.06.2024 00:01, denshi via Synth-diy wrote:
> im trying to add a reset to a CD4520 but running into an issue:
>
> in the TKB serge uses a CD4520 to handle the vertical clock (cycling 
> between four vertical rows of pots)
> here is a relevant snippet of the schematic (as found on hyperreal)
> i copy and pasted the clock input to use as the “vertical reset” and 
> am sending that to an inverter to the bottom half reset - it works, 
> but only once, and then not again until i power cycle. am i missing 
> something simple here?
>
>
>
>
> ________________________________________________________
> 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? Usemarketplace at synth-diy.org


-- 
--
synth at schmitzbits.de
http://schmitzbits.de
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20240622/df581258/attachment.htm>