[sdiy] Weird Yamaha CS40M problem

[cheater cheater]

Yamaha CS-x0 are good candidates for shotgun replacement of all logic chips.

You will probably get more help on the yamahacs80 mailing list.

Good luck.

On Mon, Oct 4, 2021 at 1:36 AM Adam Inglis (synthDIY) <synthdiy at adambaby.com>
wrote:

>
>
> On 18 Sep 2021, at 7:34 am, Antti Pitkämäki via Synth-diy <
> synth-diy at synth-diy.org> wrote:
>
> The pitch of the strange oscillation changes when changing filter cutoff
> frequency, and it ends if the filter cutoff frequency is changed
> considerably. Also turning down the resonance ends the weird oscillation,
> after which everything works normally.
>
>
> Antti, a couple of thoughts:
> • there’s no garbage anywhere on the filter PCB, you’ve cleaned, inspected
> etc etc?
> • have you been through the calibration procedures for the filter ?
> (around page 47 in the SM you linked) How does it respond?
> • you say there are very specific conditions for the oscillation to start:
> set those conditions up and examine the VCO and MOD boards as well with
> your scope. It may seem like it’s the filter board but as you say, unlikely
> both filter circuits would be faulty…
>
> A
>
>
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