[sdiy] Fwd: Looking for: AK Drummer (CRM-260) schematic

[Loscha]

The "7450" is a specialised rhythm generator chip
Not a 74xx logic chip

It sends pulse out information to the switches and so on.

I don't have any photos of the insides of mine, and the videos I have on
youtube were shot with a potato

The schematic I had is really quite incomplete
But, for modifying the voices, it should help.



On Tue, 25 Nov 2025 at 13:59, brianw <brianw at audiobanshee.com> wrote:

> I can't tell what it does without pin numbers for the SN7450. That's a
> dual AND-OR-INVERT package, so I'm not really sure what they've set it up
> to do.
>
> The 50K control in the schematic, lower left, sets the tempo, but the
> faceplate shows what appears to be a stepped attenuator rather than a
> potentiometer.
>
> Brian
>
>
> On Nov 24, 2025, at 6:36 PM, Adam wrote:
> > Pure gold.
> >
> > So... it actually only ever plays at ONE tempo, but you get divisions of
> that tempo?
> >
> > A
> >
> > <grab 2025-11-25 at 12.34.27.png>
> >
> >
> > On 25 Nov 2025, at 11:51, Loscha wrote:
> >> Hi David and group
> >>
> >>  I got one of these machines about 12 years ago
> >> And it came with the following documentation.
> >>
> >> I have a unit somewhere in my garage here in Australia.
> >> It's missing the to half of the lid I think, but has all the circuitry
> >> If it'd help you out, I can try and find it over the weekend and we can
> arrange postage
> >>
> >> Pretty sure this schematic will help!
> >>
> >> //Edward
> >>
> >> On Mon, 24 Nov 2025 at 21:56, David Huss via Synth-diy <
> synth-diy at synth-diy.org> wrote:
> >>> Hi,
> >>>
> >>> I have a AK Drummer (CRM-260) Rhythm Machine and I am looking for a
> schematic.
> >>>
> >>> I searched the web high and low. I figured out that this was also sold
> under the names Conrad CRM‑260 or CORT CRM-260 in what seems to be
> identical devices (apart from the different manufacturer logo).
> >>>
> >>> I found a 10 year old youtube video where someone has moded the thing,
> but there is no description and in a comment from 5 years ago  they say the
> documentation has been lost.
> >>>
> >>> Does anyone know a thing?
> >>>
> >>> All the best,
> >>>
> >>> David/atoav
> >
>
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