A bit of TLC for my oldest synthesizer: Jenny is getting a new potentiometer. As the synth’s pots were rather cheap, open types that gather dust, and are 40 years old now, they have become all scratchy and jumpy. As I have mentioned before, I am not the greatest fan of Kontakt spray and similar solvents/cleaners, so I bought replacements. But I never found the time to actually replace them.
This knob is a good place to start: The “glide” potentiometer is in charge of portamento, and it is one of the first things that might make Jenny fail (see Neil Johnson’s site). A faulty glide pot means that the synth will only ever play the same note regardless of which key you press. So I did replace that pot, which is pretty straightforward – you’ll find some pictures in this gallery. (It is a 2.2M linear type BTW.)
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- The Glide pot is in the upper left corner of this picture. As you can see it is sitting on a small PCB together with the Noise switch and pot. Remove the knobs and the nuts from the axes of all three, and you can take out the board to replace the potentiometer.
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- The pot needs to have a 10mm shaft and a 5mm diameter axis. Cut off the axis at about 10mm – which makes the distance from the end of the shaft to the top of the pot 20mm.
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- Pot soldered and screwed to the PCB. Ready to re-insert and re-attach the board into Jenny’s panel.
Overview of potentiometer values
This is an overview of the potentiometer values, some of them are linear, some logarithmic, a few antilog. The most obvious candidates for replacement, apart from the glide pot, would be Frequency (100k) and Resonance (100k) for the filter, and Tune (10k).