[sdiy] Cheetah MS800 Internals pictures

Steve Lenham steve at bendentech.co.uk
Mon Jun 7 12:10:02 CEST 2021


On 05/06/2021 17:37, Richie Burnett wrote:
> A few photos for your viewing pleasure:
> 
> http://www.richieburnett.co.uk/temp/MS800/

Great stuff! Thanks Richie.

> When I take the main board out to change the battery, I'll stick it on 
> the scanner and get a picture of the bottom side tracking too.

Yes please! All we would need then is the two EPROM images and the bold 
reverse-engineer would have everything he needed ;-)

> Incidentally the SGS wavetable chip runs quite warm to the touch!  It 
> also uses some sort of pulse-amplitude-modulation to output multiple 
> voices to the limited (2) audio outputs.  There's little attempt made to 
> filter this at all, and the multiplexing is clearly visible in the 
> waveforms from the output jacks.  Aliasing / Imaging is something this 
> synth does in spades!

Let's face it, if it didn't then we wouldn't be so interested - it would 
be forgotten as just another characterless "ROMpler"!

> M114S wavetable chip datasheet: 
> http://elektronikjk.pl/elementy_czynne/IC/M114S.pdf

Good find. I only had the preliminary datasheet for the larger M114A. 
The A version appears similar but appears to extend the amount usable of 
data ROM; whether it ever saw the light of day is uncertain.

Neil Johnson maintains an archive of the M-series datasheets:

https://www.njohnson.co.uk/index.php?menu=2&submenu=5

and will probably want to add this one to it.

And in response to one of my own previous wonderings, here is a list I 
stumbled on of instruments which use the M114:

https://synteknik.com/vintage-chips/m114-s-sgs-st-integrated-circuit-m114s/

Cheers,

Steve L.
Benden Sound Technology


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