[sdiy] Cheetah MS800 Internals pictures

Richie Burnett rburnett at richieburnett.co.uk
Mon Jun 7 14:45:58 CEST 2021


> All we would need then is the two EPROM images...

I'll see what I can do.

BTW, Feel free to copy, use, post the MS800 images on your own site or 
anywhere that you want to.  Distribute freely if you think they're likely to 
be of interest to anyone else, as I'm unlikely to find the time to put up a 
web page dedicated to the MS800 myself!

Best regards,

-Richie,



-----Original Message----- 
From: Steve Lenham
Sent: Monday, June 7, 2021 11:10 AM
To: synth-diy at synth-diy.org
Subject: Re: [sdiy] Cheetah MS800 Internals pictures

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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