Sequential Circuits Pro-One

I have finally started restoring my Sequential Circuits Pro-One. My plan is to get it as close to mint condition as possible and start using it again for recording and perhaps performing. Once I started using the Korg MS2000, I neglected the Pro-One and it fell into disrepair. Over time the key contacts became dirty and inconsistent. At some stage one of the knobs was broken off and lost, leaving a stub of potentiometer protruding uselessly from the control panel.

The first thing I did was clean the pots. For you laymen, pots is short for potentiometers. In other words, I wasn’t diverted by dirty dishes. To clean the pots I removed the knobs and then squirted a few drops of a greaseless lubricant called LPS-1 around the post. The stuff works wonders on crackly volume knobs and was recommended to me by the electronics experts at AEI Electronics in Minneapolis years ago. I’ve been using it ever since. After applying the LPS-1 I made thirty or more rotations of the pot from zero to maximum so that the dirt particles were worn away by the fluid.

I put the thing back together and did some tests. The knobs no longer had anymore crackling going on, so that was fixed, but the keyboard was horribly inconsistent. The Pro-One uses a J-wire keyboard with open air connectors that are prone to collecting dirt (or residue from malted beverages spilled over the keys). For a close up view of the Pro-One J-wires check out this post on MaxtrixSynth. Another problem is that the J-wires can become less springy, making the connections a bit weak. I used used q-tips with a drop of LPS-1 to clean each J-wire and the metal bar that they connect to when the key is depressed. I also bent the J-wires slightly to improve the tension. After all that I tested it again to find it working flawless, although still a little difficult to tune. Next up I’ll be replacing the missing mod wheel, the broken potentiometer, and the missing knob.

9 thoughts on “Sequential Circuits Pro-One

  1. Good luck with the restoration, it will surely be worth it! I have never played a Pro-One myself but I’m pretty sure it was used on “Sweet Dreams” by Eurythmics, cool sounds and that sexy Curtis filter chip!

  2. Oh, wow… Just found this through a friend. My Pro-One is needing very similar treatment. Looking forward to seeing the rest of this project!

    Where did you get a replacement pot? I’m having a hell of a time with that. Wine Country seems to be permanently out of stock of the one I need (the 4-position octave selector for Osc. A).

  3. I have my last two knobs on eBay right now.

    Also, with the key contacts I discovered that replacing the DIP sockets on the PCB’s at either end helped a LOT with key contact behaviour. The sockets oxidize somewhat and the increase in resistance means that the J-Wires need to be in really good order. When the sockets are new (double-wiping) then the unit is more forgiving of poor J-Wires.

  4. @thorn I got the pot from a site called http://synthwood.com. They don’t sell parts specifically, but I saw that they do Pro-One retro fits (really crazy ones with lots of wood and glowing pitch/mod wheels) so I emailed them on the off chance that they would have what I needed and luckily they did.

  5. @GB Okay, thanks!

    @John Ah yes, synthwood.com… I’ve drooled over their site a number of times. Didn’t occur to me to see if they’d sell just a part.

  6. Thanks for the photo’s they really show the keyboard bed nicely. I have a Pro ONe but with the Membrane keyboard bed (without the J-Wires). Do you have any idea where to get bushing for it? And secondly, seen any blogs with photo’s doing repairs on that version of the Pro One? Really appreciate any help. Thanks, Pat

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