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

[brianw]

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
>