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MOTM-800 how to convert old version to rev B

MOTM-800 how to convert old version to rev B

2014-02-24 by <Frank.Hettlich@...>

I have a couple of older MOTM-800s (possibly pre-2000) that I would like to convert to the "recent" rev B version (you can easily tell if yours is a rev B as it is written on the pcb). There is a website that describes the procedure quite in detail (see link below) even with references to Paul Schreiber approving it:

http://www.google.de/imgres?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&biw=1680&bih=898&tbm=isch&tbnid=RIpBnPtYWxekWM%3A&imgrefurl=http%3A%2F%2Fwww.wiseguysynth.com%2Flarry%2Fmods%2F800_rev_B.htm&docid=-4VuitXRK7pqZM&itg=1&imgurl=http%3A%2F%2Fwww.wiseguysynth.com%2Flarry%2Fmods%2FImage536.jpg&w=668&h=397&ei=a_3wUqOwNMeR4ATizIDoDQ&zoom=1&iact=rc&dur=1440&page=1&start=0&ndsp=43&ved=0CIoBEK0DMBE

Unfortunately one of my MOTM-800 that is obviously modified according to these instructions does not behave like my rev B.

With attack to zero, decay and sustain in mid position and release to zero my rev B works as expected, i. e. when the gate signal is off the envelope immediately returns to 0v whereas the modified one still seems to be in the sustain phase (at least for a while). This is a typical behavior when there is no gate input patched and the sustain of the MOTM-800 works as a voltage source.

So the questions are:
- does someone have the old schematics (so I can compare the different circuits)? Paul“s "docs" website offers only the rev B.
- did somemone successfully convert an older MOTM-800?

Many thanks in advance

Frank

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