Fixing monophonic pedalboard on a home-upgraded digital organ. Replace MIDI board?..

[ramendik]

Hello,

We are looking at acquiring an organ that was made into digital DIY in, apparently, the 90s. It uses a Viscount expander box to make the sounds. To feed the expander box it uses a MIDI board. The two manuals and the pedalboard all appear matrix-wired, judging by the number of wires.

The manuals play just fine. But the pedalboard is monophonic. Moreover, if you press pedal A, then press pedal B, and then release pedal A, you get silence.

To use this organ I need to upgrade it so the pedalboard can make at least two sounds at once. The seller is quite willing to help with doing it but we need to know how to do it.

Would replacing the MIDI board work, and if so, what board do we need? Or do we have to rewire the pedalboard - and for what/how? Advice would be much appreciated.

I have made a photo of the MIDI board in the organ. The photo is at https://pasteboard.co/IgETdW4.jpg

Thanks!

[ramendik]

Upon more research, the console (pedalboard and manual) turned out to be an old Norwich analog organ repurposed for digital in the 90s, DIY.

Might the wiring of the pedalboard be the problem? If so, can I perhaps rewire it, with diodes if necessary? And would I have to replace the MIDI board to take advantage?

I hope to be running tests with a computer soon (just need a MIDI cable). If the problem does turn out to be on the "before MIDI output" side, I will take care to inspect and photograph the wiring of the pedalboard.

[toodles]

Analog organs, especially frequency divider organs, provided monophonic pedals, by using a separate divider for the pedal notes--the pedal key switches might be wired in series through a staggered SPDT wiring to provide a lockout of higher notes on any pedal. If your organ used such a scheme for the analog voices (originally) perhaps when modified for digital they left the pedal wiring intact. Should be a matter of rewiring the pedals to provide a parallel output--i.e., one wire for each note.

If your MIDI encoder permits multiple notes to operate it should just require rewiring the pedals.

[ramendik]

The MIDI encoder is photographed at https://pasteboard.co/IgETdW4.jpg and is from the 90s. It does not seem to have enough pins for a parallel-output pedalboard (the pedalboard connector is on the lower left). So it probably wants matrix input.

Would this MIDI encoder board be programmed for SDPT? Documentation for reprogramming might be hard to come by so I might have to get a new MIDI board? And could you possibly point me to some diagram or otherwise explain how staggered SDPT wiring works? I do understand how matrix works and how parallel works but not staggered SDPT. I know that SDPT is a simple relay, but now how they are staggered.

Another thing that puzzles me here: what we need here is not really pedal polyphony as such. It is legato playing. Note B is pressed then note A released - and note B ends up not played at all. If note B started playing when note A is released, we would not have a problem.

If this is just a matter of wiring, then the moment note A is released, the MIDI encoder would notice note B pressed? Why is this not happening?

I really need to understand more about how such wiring works with a MIDI encoder. Explanations and any sources would be very much appreciated.

[Admin]

It seems to me that simplest way to approach this is to re-wire the pedal board for parallel output. You can use an encoder such as the one linked to below. If instead you want to understand the current configuration first, the only way you're going to be able to do that is to examine the connections to the pedal switches and see how they are wired. As you say, this appears to be a DYI conversion so no one here will have a diagram from which to properly advise you on how to proceed.

[toodles]

It is rare when a photograph of an electronic circuit board can provide enough information as to how it works and is intended to be wire--such is the case here.

What you need most is documentation on how that encoder is supposed to be wired. Without that, everything is just guesswork.

Staggered SPDT wiring works like this, on analog organs with audio keying: Each note switch gets signal applied from its appropriate generator (C note switch gets C signal, C# note switch gets C# signal, etc.) applied to its NO contact (normally open); The switch common for the C note switch is the output for the switch string; the C note NC contact is wired to the C# Common, etc. up the chain; when any note is pressed it disconnects the signal from the switches above it and sends that signal to the notes lower than it (unless they are pressed). Thus the output of the lowest note is the signal from the lowest key that is played, and this is sent to a pedal frequency divider.

[ramendik]

Thanks! I will review all notes that might exist for this organ. And also, using your description, I will try to decode if a staggered wiring still exists. I am planning to be there tomorrow.

Of course the nuclear rewiring option exists. Just remove all wiring from the pedalboard, leave the bare contacts, and wire them anew for a new MIDI board. Looks like I can get the required board from midiboutique.com, along with the "spreadboard" that will let me just wire every contact individually without bothering with creating a matrix, for under 100 Euro. I wrote to them now asking about it.

[ramendik]

To the people who helped me out here - thanks a lot! Armed with all the knowledge I came in and investigated.

The pedalboard is wired well (as far as I could understand, it was rewired as a matrix). The problem is with the Viscount EXL 150, which fails to note a Note On for the pedal once a pedal note is already playing. With Hauptwerk the entire console plays well.

Moreover, the EXL 150 turned out to have a working MIDI Thru output. So I can still run the manuals with the EXL 150, which has very nice sounds and works with the stops and pistons on the console - I just push its pedal volume slider to zero. I attach a Hauptwer-running laptop to the MIDI Thru (with a MIDI-to-USB cable) and play just the pedal with that. A mixer is required for the outputs, I just happen to have one (the Roland Cube has this functionality).

[cjfox]

If the midi encoder shown in the photo encodes both the manuals and the pedals, your problem is in the original pedal wiring. The matrix is looking for switch closures, and will trigger the note it is programmed to trigger, normally polyphonically. If the manuals work fine, then the encoder will se the pedal switches as just an extension of the keyboard matrix. Wire the pedals with same scheme as the manuals, and it should work as you want.

[cjfox]

I just saw that you got Hauptwerk to function correctly. Glad you solved it.

[John_Joe_Jr]

Hi ramendik . I'm only noticing this thread now as I wasn't on the forum when it was originally posted. I see that you live not that far away from me? If the organ that you have described is the same one that I think it is, then yes, I remember seeing photos of it on the seller's website. Obviously I won't be able to see it for myself for quite some time yet what with the whole pandemic situation at the moment, but any chance of a few images of the new setup that you have put together?