My SCI Pro-One Project

A few months back I got very lucky on an eBay auction. Someone had listed a Sequential Circuits Pro-One in a slightly strange category with an absurd "buy it now" price and I jumped on it!

When it arrived, I realized it would be quite a bit of work. It was really filthy with layers of dust and someone had marked his favorite knob positions on the panel with ruby sparkle nail polish! The key bushings were dried out pretty badly, the output jack was damaged and there were some scratchy pots and coarse-moving switches. Worst of all, the pitchwheel was broken in half!

Surprisingly, electronically it was fine...all functions worked!

I ordered a set of new bushings from Archive Sound, some Deoxit and Faderlube from Caig Labs and decided to spring for a hardwood cherry case from Synthwood. The case from Synthwood also includes case "badges" and a Dave Smith Instruments wheelbox so that also solved my broken pitchwheel issue.

With the arrival of the last of the supplies, I was ready to begin. I started out by giving it a quick wipe-down with a shop towel and setting it on my work surface:

I removed the wood sides and four screws on the bottom and the keyboard was out.
At this point I was careful not to damage any of the exposed J-wires as they are easily bent.

I also took this opportunity to banish my cat to another room! =^.^=

Flipping the keybed over exposes the bushings:

The bushings can be removed without the disassembly of the keybed itself with the aid of an X-acto blade and some dental tools.
The new bushings await their turn:

I just sliced down the length of each old bushing and extracted the detritus with the dental tool:

Slicing them first enables them to come off (usually) in one piece:

After making sure no particles were left behind, the new pre-lubed bushings were so slippery, they just pushed on smoothly with a fingertip or, in some tight areas, with the help of a pair of needle-nose pliers.

At this point I cleaned the control panel and carefully scraped off the nail polish with the X-acto knife.

I test fit the case, chassis, wheelbox and control panel:

The original metal bottom plate needs to be used for the refurb but one of the press-nuts has come loose...this will have to be reattached:

I have some 3M DP-805 handy, a non-epoxy, high-shear-strength (2780psi) glue that retains some flexibility so it will be perfect for the job:

Being careful not to get any glue in the threads, the press-nut is reattached:

Now I'm ready to get to work on the circuit board.
In the Pro-One, the pots, switches sound generating circuitry and power supply are all mounted on a single board:

I lube all the switches and pots by squirting in a small amount of Deoxit Faderlube and working the unit gently back-and-forth a number of times.
I'm using the 5% stuff so as not to gum up the switches and pots with residue.
(Regular Deoxit "contact cleaner" is not recommended for this particular job as the carrier can be antagonistic to some resistive elements, I'll use it later for the busbar and J-wires.)

The 1/4" audio output jack has been damaged very badly so its replacement is necessary.
One of the lugs is very close to a resistor's connection to the board so I've attached a small heatsink to the resistor's lead to keep it from overheating:

A solder "sucker" is used to remove solder from the old jack's pads:

You can see how screwed up the old jack was...someone must have tripped on a cable plugged into it.
The new replacement jack is on the left.

...and moments later its soldered in place:

Now on to the busbar and J-wire cleaning.
A small amount of regular Deoxit is applied to a lint-free swab:

...and very gently rubbed on the area of the busbar and J-wires that contact:

Afterward, I wipe the busbar and J-wires with a clean swab to remove any Deoxit residue.

Now on to the chassis modification for the wheelbox.
I've placed some white labels down in the area where the screwholes will need to be:

...I've inserted the wheelbox screws in upside-down so the ends protrude downward:

I put the wood case in plase over the metal, then fit the wheelbox into the area it will go.
I press down so that the screwtips leave an indentation on the white labels: I can use a starter punch to mark my hole positions in the metal:

Then, I remove the labels and drill the holes where I've dimpled the metal:

The control panel is installed into the case with T-nuts:

The circuit board is attached to the control panel:

Ready to assemble the case.
The wood trim in front has to be in place before the keyboard is attached.
The keyboard and wheelbox are only very loosely bolted in at this point to provide some "wiggle room" during assembly:

I partly lower the case and connect the keyboard, wheelbox and power cables:

Attach all the case serews, tighten down the wheelbox and keyboard, replace the knobs and we're nearly there!

Once the case badges are applied, its finished! Even my cat approves:

This was a fun personal project for me and I hope you all enjoyed it!
While not intended as a definitive or "proper" tutorial, I hope people have found this useful and interesting.
With the focus on hardware, sometimes its easy to forget its about making music...and now this Pro-One is definately ready for that! :)

What you give is what you get.

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