Jen Electronics SX2000 Synthesizer

[earache]

Hi Folks

I have an old monophonic Italian synthesizer, a Jen Electronics SX2000, and I would like to figure out how to tune it.

Specifically the instrument is not in tune with itself across the keyboard and I wonder how I can adjust that?

The manual and schematics are attached here. The text appears to be French or Italian, but the schematics are at the end of the document and all notes are in English there

Thanks In Advance

Earache

JEN-SX2000-doc-Utilisateur-Service.pdf

[Mick Bailey]

The keyboard is a constant current/resistor type and the resistors are likely to be stable. There is an OCT.CAL trimmer shown on the schematic. I'm thinking this would be used to set the octave intervals in tune. The individual notes are determined by the 10R resistors associated with each key and cannot be altered. If the octaves are in tune, then the note intervals should be as well.

If this was mine, I'd locate the trim pot and mark precisely where it's currently set then experiment to see if it will bring the first octave in tune, then check the rest of the keyboard. Sometimes there's a compromise and you have to accept some discrepancy. If the trimmer is a single turn rather than 25 turn it may be a challenge.

[dmeek]

After adjusting the scale with the Oct-Cal trimmer, center the Tune slider, set the Octave switch to 32' and adjust the pitch to A440 with the Freq. Cal. trimmer. Then adjust the pitch of the other octaves 16', 8' and 4' with their own pitch trimmers (page 12).