2 manual Zimmer console conversion - Initial steps

I was fortunate to be able to acquire a 2 manual console which I'm in the process of converting to a Hauptwerk controller.  St. Paul's Lutheran Church had had their 16 rank unified Zimmer in storage for 2 years, having left their building in Laguna Beach in search of a place in Irvine.  With no end in sight with respect to a new permanent home, they decided to reduce their storage costs and give me and my friend and organ builder Ryan Ballantyne (http://www.rmballantyne.com/) the entire organ.  The pipework and chests were taken by Ryan for repurposing, and the console was left with me, as Ryan didn't feel it appropriate to use it in a church installation.  Two of the ranks from the St. Paul's organ are already in place at St. John's Lutheran in Orange.

It turns out I picked up a 2-manual Moeller console on the same day, but we felt due to the quality of the console, it would be a more appropriate console to repurpose for a rebuilt pipe organ, so I ended up with just the Zimmer console.  My wife was glad.

The first step is to clean out all of the obsolete and superfluous circuitry.  As all of the memory and combination system will be taken care of by the computer under Hauptwerk, any of this can be removed.  The only objective is to retain all of the switches and wiring to the Syndyne Stop Action Magnets.

 The rack of equipment containing the combination system above the crescendo was removed, along with all of the Peterson coupler action pieces, and the power supply.  The plan, since the power consumption is orders of magnitude lower, is to simply use small power supplies for the MIDI equipment.  Doing the math on the SAMs, there are 28 of them at around 30 ohms.  At 12V, it's 1 ohm if all of them are on at the same time, so it's easy to find a 12A 12V power supply, if no other place, than with a standard 300W PC power supply.  This supply is far more efficient, and lighter than the goat anchor here in this console.  I think by removing all of this equipment, the console is half the weight that it was before.

 I'm using MIDI scanners from a company I found online called "MIDI Hardware" (http://midi-hardware.com/).  Roman Sowa runs the company from his home in Poland.  The circuits are small yet robust, and very inexpensive compared with other alternatives. 

After removing superfluous wires, I wired up the keyboards.  The console was built with pins for each switch and a common ground.  This made it easy to wire ribbon cables up to them, and then run them to the scanner hardware.

Fully wired keyboards are run to the Midi-hardware scanners through the ribbon cables SW on the left, GT on the right.  I'm planning on adding a 3rd manual, since hardware is so compact now.

The pedal was a different story.  The original design of the instrument had the switches for the pedals wired into the console.  This is heavy, bulky, and limits flexibility.  I decided to make the pedal a completely stand-alone MIDI pedalboard, with its own scanner and MIDI output.  This required some rewiring of the switches from a common ground system to a matrix system.  Diodes were added in order to support the inexpensive scanner design.

MIDI output for the pedal board, along with a USB connector for power.  Better would be to have a USB MIDI system, but that hardware is way more expensive.

The switches had been sitting unused for 2 years.  These switches are 2 wires wiped by a copper bar.  After completing the installation, I found that they don't work very well.  I'm going to have to replace them with reed switches before the instrument is usable.  Even after cleaning the contacts, they don't work very well.  I suspect it has a lot to do with the fact that the original system actually drew quite a bit of current through the switches, which tended to hide a lot of keybounce issues.  With modern systems, they really don't work well.

Then there were the Stop Action Magnets (SAMs).  In this system, the reed switches were reference to 12V and the magnet coils were referenced to ground through big bus bars across the top.

The diode array coming in the back is for the SFORZ action, which is unnecessary in the new system.  Ground is on the right, connected to one end of the magnets, and +12V on the left, connected to the switch.  Conveniently, though it's very straightforward to reverse engineer, Syndyne gave the patent number 3832658 which provides some details on how they are hooked up.  I've built a circuit which will drive these magnets, since you want momentary actuation of the magnets.  This simple circuit will bring in the MIDI state change for the stop, and look at the edges and create a short (probably 200ms-400ms) pulse to energize the ON or OFF magnet.  However, it's way more convenient to have the switch referenced to ground so you can use a ground referenced scanner to determine the state of the switch, and the magnet coils referenced to 12V so you can use N-FETs to drive them on.  Fortunately, there are no active circuits on this board, so all I have to do is swap the bus rails and drive the right one to the coils at 12V and the left one to the switch at GND.

So left to do is

1) Reed switches for the pedalboard
2) SAM drivers
   a) write microcontroller code
   b) Test and install using the Midi-Hardware LITSW stoptab drivers
3) Wire up the peripherals to a scanner (Pistons, Toe Studs, Swell mechanism, Crescendo mechanism)
4) Add the 3rd keyboard