[sdiy] Cheetah MS800 replacing NiCd Varta Mempac

Richie Burnett rburnett at richieburnett.co.uk
Sat Jun 5 12:51:30 CEST 2021

It's SGS M114S. I'll upload some pics of the inside later when back at the PC :-)

Thanks for all the battery suggestions everyone, 


Sent from my Xperia SP on O2

---- Steve Lenham wrote ----

>Any chance that you could post some decent pics of the MS800 circuitry?
>The MS800 is one of those units that has become mythical mainly because 
>there is hardly any solid information about it in free circulation, so 
>it can be whatever anyone wants it to be. I'm curious as to what the 
>fundamental sound generation circuitry is based around.
>Now, I was about to post the following:
>"No offence to Cheetah, but they were not the sort of firm that I would 
>expect to have developed some unique circuitry. Much more likely that it 
>is a clever (or not!) implementation of something off-the-shelf.
>I'm guessing either:
>1. One of the early Dream Synthesis digital synth ICs (like in the 
>Evolution EVS-1).
>2. One of the SGS(ST) ROM playback chipsets designed for organs (Mxxx 
>3. Perhaps something by TI Italy (TMS3xxx series)."
>...when I thought that perhaps I should do quick Google to see whether 
>anything new had been discovered recently. And there was a little.
>According to Vintagesynth, the MS800 was designed for Cheetah by an 
>external consultant, Mike Lynch of Lynett Systems. And the consistently 
>reliable polynomial.com reveals that it does indeed use an SGS chip 
>reading waveform data from a 27256 EPROM, with a 6502 CPU managing the 
>They can't read what the IC is since it is covered with goo, but I would 
>put money on it being the M114. Polyphonic? Tick. Multitimbral? Tick. 
>Reads waveform data from EPROM? Tick. Can you confirm, Richie?
>For those tempted to have a tinker, the M114 was definitely used in '80s 
>digital organs. It would be good to identify which ones. I picked up a 
>set of four PCBs from an unknown organ on eBay for peanuts - each 
>contains two M114s reading data from EPROMs labelled "Celeste", 
>"Diapason" etc.
>There seem to be at least two versions - my boards use the M114S, which 
>has 40 pins, while the datasheet I have is for the M114A which has 48 
>pins. Polynomial's photo of the MS800 shows 40 pins.
>So anyway, all we need is for Richie to trace out the circuitry of his 
>MS800! We can then make MS800 clones using cheap organ parts and get 
>rich selling them to Aphex Twin fans :-)
>I love me a bit of nerd archaeology :-)
>Steve L.
>Benden Sound Technology
>P.S. Re the battery, just fit the NiMH replacement and check it every 
>ten years for signs of leakage starting - or more regularly if you allow 
>it to sit completely flat. Although one should always do due diligence, 
>at that level of charging current (1.4mA!) there really won't be any 
>NiCd/NiMH compatibility issues. Extending it off-board is also a good 
>insurance policy, if you are willing to put in a bit more effort.
>On 04/06/2021 19:34, Richie Burnett wrote:
>> Lol. Richard D James has got a lot to answer for! It's a totally bonkers synth, with a very gritty sound.
>> -Richie,
>> ---- Gordonjcp wrote ----
>>> On Thu, Jun 03, 2021 at 03:29:59PM +0100, Richie Burnett wrote:
>>>> I would be interested to hear your thoughts!
>>> The overriding one I have is "I wish I hadn't passed up that MS800 that was in Vic Morris for 50 quid about 15 years ago..."
>>> -- 
>>> Gordonjcp
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