TR909 Extension

TR909 the queen of drum machines. No much more to say about this one, you love it or hate it. I do certainly love it!
The circuit is build in a way which allows a lot of extension work, as it is an almost modular concept.

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The memory expansion slot had to make place for the connector of the extension box. Of course, the unit can be re-modified to its original version in within a couple of hours, no irreversibly changes have been made.

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Also, on this unit, I replaced the firmware eprom with one holding the latest (or last software version if you can say so for a unit of this age) firmware,
which is known to have a better clock sync-timing. Important for recording sessions…
Got another one, which I repaired, but it was in such a bad state once I got it, that I was too disgusted to take any photos of it. This is how it looks now.

Finally done!

Did I mention that it didn’t work when i got it? it surely does now!

A service manual for the TR909 is available on Matrixsynth but I bought mine before it was available on the net from Mark Glinsky’s manual manor who is always a good source for nicely copied service manuals and schematics.

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