Sequential circuits pro one with mtg9/14/2023 ![]() ![]() A few nice touches that remind you that you are performing surgery on a lovingly designed artistic instrument, not just another mass produced piece of electronics. There is an elaborate Buddha, some ancient / alien looking symbols and even a cluster of mushrooms and flowers all imprinted in raised silver. (I always wait several hours before powering up a circuit board after cleaning it with any solution) The circuit board itself had a surprising amount of artistic customization. I started by cleaning the board with a small amount of alcohol on paper towel and q-tips. Now it was time to clean up circuit board, repair loose connections and recondition the pots and switches. The wood sides were in great shape and only needed some furniture polish. The outside shell needed some light soap and water, and a bit of all purpose orange cleaner. Most of the basic internal cleaning was done with air bursts and a small amount of 90% isopropanol alcohol on a rag. I half expected to find a dead rat wedged in there. Step number one was to completely break down the Pro One and clean every square inch! There are plenty of tutorials out there on how to take apart a Pro One, so I will not go through every screw here. Deoxit F5 is a fader lube and it works wonders on sticky / frozen / scratchy faders, pots and switches. ![]() Many of the problems with this unit were simply fixed by cleaning the connections with D5. Deoxit D5 is a contact cleaner and an amazing tool for cleaning and caring for vintage electronics. 90% isopropanol alcohol is usually a good cleaning choice for electronics since it evaporates so quickly. I hunted for a serial number below 8500 to ensure that I was dealing with the J-wire keyboard setup, but above 1500 to avoid having a unit with the main power supply mounted to the circuit board which reduces durability.įirst let's talk cleaners and solutions. ![]() The Pro One's with serial numbers under 8500 are equip with the stable and easy to repair J-wire style keyboard, while serial numbers above 8500 have the more troublesome and difficult to repair membrane keyboard. Pro One buying 101 starts with serial numbers. There were a few other problems, but I don't remember them now. The housing was dirty, the pots were scratchy, the unit only powered up intermittently, the audio was buzzy, the keyboard keys were uneven and several were non-functioning, at times the unit only produced noise in the drone mode and the CV pitch and note scale were off causing out of pitch notes no matter how carefully you tuned the oscillators. We stress that if you attempt the job yourself that you must wear safety glasses and be careful not to lose the little springs that you will need to remove.Sequential Circuits Pro One (Repair and Reconditioning)īuying a mint Pro One was not an option at today's high prices, but I found a good deal on eBay and was convinced that I could recondition it myself. ![]() They can be replaced by anyone that is reasonably handy and careful, the suppliers provide directions on their respective web sites. These bushings have been reproduced by several enterprising people and are available for a reasonable cost. This is a common problem and easy to repair. After so many years the rubber bushings dry out and the keyboard becomes noisy and uneven. The Pro-One uses a Pratt-Read keyboard mechanism in common with many American synthesizers. test every pot and switch, especially check all of the waveforms on the VCO’s and LFO, it’s not unheard of for a CEM3340 VCO to lose one of it’s waveforms while the others still function. Look for the obvious – Cosmetics, pots not excessively wobbly and not scratchy, smooth, even key action, jacks clean and not intermittent, bend and mod wheels smooth and working. Take your time, read the manual if you need to before you go to inspect the synth. When trying out the synth the golden rule is to test EVERYTHING. It’s worth paying a buyers premium for a good example of the machine of you can find one, if you ever choose to sell it in the future you will see a return. As with any vintage synth the condition of the exterior tells a story and usually reflects the condition of the interior. ![]()
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