Looking to convert a 1970’s Allen

There are two approaches to controlling Allen stops to my knowledge, at least without doing extra modifications to every SAM's driver board (Artisan). Zuma Group has a replacement for the Allen capture board for consoles which remain playable with their original electronics. I have a free design that is intended for stripped down consoles.

The reason generic decoders are not appropriate choices is because of the higher voltages but more importantly because rather than operate a single SAM at a time, Allen pulsed a whole division at a time whether or not individual stops needed to move. This makes a decoder solution impossible without major rewiring or else using the Allen's own capture supply with its five individually switchable outputs which need to be controlled by the decoder. A control line to each driver board is set to determine whether the stop will turn on or off. Then the decoder pulses one of four capture supply inputs which sends a 50V pulse to an entire division's SAMs. This allows a simple CMOS control signal through a 1.5k resistor to operate the stops -- the usual hefty driver board isn't required as the drivers are on the individual SAMs. It is a nifty arrangement which requires a specialized decoder.

I got a chance to ask about using the decoder, etc from https://www.midi-hardware.com which he did with quite some amount of work. But in his case none of the original Allen boards could be used as the instrument was struck by a power surge, probably lightning.

He told me he cut free all of the Allen electronics and individually wired the SAMs to Roman's decoder boards. End result appears to work well. All the control is via Hauptwerk.

Rgds,
Ed

We are currently converting a 3-manual Allen 903d using John Kinkennon's MIDI kits... we're getting close to the finish line... all the keyboards are wired up and the pistons and drawknobs are next...

So far it is working very well.

I plan to post some information in a few days - including keyboard wiring diagrams.

Be aware that the Artisan approach requires modifications to each SAM's driver board. With a large number of stop tabs or drawknobs this requires many hours of tedious work.

I was lucky enough to have the original capture circuitry still working. All I had to do was route the yellow sense wires coming off of each stop switch to a corresponding terminal on a serial input board dedicated for the stops. The original Allen board and power supply still handles all the SAMs.

Artisan has an input board designed for the 6x10 matrix Allen keyboards. However, I couldn't use it on my console because the Artisan board is designed for keyboards that have the highest C as the orphan. Mine was wired with the lowest C as the orphan. I could've walked everything down but that would have been as much work (if not more) as wiring each key directly to a serial input board. Since I already had the input boards from a previous project I just decided to use them and be done with it.

I'll have to dig out my notes and see all what I did.

Bill S.

That makes sense. If you are willing to use the Allen capture system that would work partially. Still the lack of control of stops movement allows the stops to get all out of sync with Hauptwerk. The yellow or white wires are easy to read which gets you the inputs to Hauptwerk. Any combinations stored in Hauptwerk cannot control the green wires without the methods I've recommended, so you would need to keep the Allen circuitry running and still would not have HW control to move the stops and keep them in sync.

If that's good enough then stick with it. I see that Ed and I were failing to communicate as I assumed that controlling stops meant taking advantage of the SAM's ability to move the drawknobs or tabs under HW control. An actual decoder is required to take full advantage of Hauptwerk's capabilities.

Yes - I am using just the Allen capture (and limitations thereof) for now and it's totally separate from the sound engine.

If/when that Allen capture board goes kaput I'll take advantage of Hauptwerk's capture capabilities and make the modifications that you have mentioned. Sounds like a good rainy or snowy weekend project.