Pro-One Calibration and J-Wire Cleaning

I recently cleaned the j-wires and re-calibrated my Sequential Circuits Pro-One. I cleaned the j-wires and the contact bar with isopropyl alcohol and cotton swaps, although proper contact cleaner is recommended. I also gently bent a few of the wires to improve the connection to the contact bar.

I knew about the calibration problem prior to any of this maintenance, but I noticed it even more after cleaning the j-wires. I’m not sure why this would be the case, but I resolved to take a stab at the calibration myself having not attempted it before. Looking on the scope I could see that an octave on the keyboard was actually a quarter tone sharp and therefore unplayable. I made the necessary adjustments for both oscillators and now it sounds great.

After the calibration I produced this sequence entirely on the Pro-One in a single take by programming two short sequences into the on-board sequencer. The first sequence was played at several pitches to create a progression. I also switched off the oscillator sync at the same time I switched to the second sequence to create an octave doubling of the melody then re-enabled the sync at 1:41.


11 thoughts on “Pro-One Calibration and J-Wire Cleaning

  1. sounds like you really know what your doing. I have a Pro One but it’s the membrane model (not the J-wire model). Do you know if the membrane uses the same type of bushing as the j-wire version? Thanks for any help. Pat

  2. Just replaced my keybed inside my Pro One with a Fatar 37-keyboard and just need to calibrate it. Anybody know any tricks or things to be aware of to calibrate this synth. I have a copy of the manual and see it discussed beginning on page 26. Right now all notes play but they all play the same tone. THanks, Pat

  3. If it only plays one pitch the entire length of the keyboard it sounds like you have the KYBD switch off in the Oscillator B section. When the calibration is off you get notes that are sharp or flat an octave or two apart.

  4. John thanks for the tip. I am at work now so can’t check it till I get home tonight. I sure hope that’s the issue!!!! That would be a small miracle. Been reading up on how to calibrate it and it seems pretty involved.

  5. Hi guys,

    I too have a j-wire Pro One in need of calibration so if you have any tips beyond the 4 lines in the manual that would be greatly appreciated. I am certainly a novice in this area, but am confident I can find my way through with some guidance from more experienced hands.

    The voltage readings I’m getting from the CV out are really strange, inconsistent, sometimes negative and bare no relation to the 3V difference from C0 to C3. Some keys trigger the same tone, patterns of notes repeat and in no way follow a scale. Moving up the keyboard can give lower seemingly random notes although the keys tend to keep the same tone whenever you trigger them. Scaling is way off so I’m wondering if I have a more fundamental problem that just calibration.

    I’d really like to get it back to it’s former glory. Cash is tight so I’ve not yet bought the bushes which certainly need replacing, but I thought I’d see if could get it to step though the 3 octaves with it’s clunky keyboard first.

    Apologies if I’ve put this in the wrong spot. Keep calm and Mellotron!

  6. @DanH. Hmmm… Sounds beyond my level of expertise. I’d start by cleaning the j-wires and the contact bar. Also, make sure you have the KYBD switch on in the Oscillator B section.

  7. Thanks for replying John. I spent 3 hours re-calibrating last night (which I really enjoyed as a one off!) The voltage difference between C0 and C3 is now exactly 3V. Hoping that the cleaning will make all the difference.

    Oh, your sequence is a great little piece. Hope I can manage to get something similar out of mine soon!

  8. Hi Dan, were you able to fix the calibration problem? I just got a J-wire version but the C sounds as F. Do you have similar problem?

  9. Hey Alan. You should be able to tune the oscillators with the frequency knobs, otherwise there are little hole nearby for calibration.

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