Diodes and keyboard contacts

[sweetbb]

I am busy midifying a 1972 Yamaha console style organ, using a Midi Moutique midi encoder. I think the Yamaha organ is a model
E5. There are numerous contacts per key, on both manuals. However, there is
a metal bar above the contacts as well, reminds me of change over contacts.

Will this be a problem? I am creating an 8x8 diode matrix as required by my
midi encoder, utilising two of the contracts per key.

When the keys are not being pressed, 8 keys will be in contact with each other, via this 'bar' above the keys. Will this
have any influence on the system?

[geoelectro]

Question, are you totally re-purposing this organ or adding MIDI, while keeping the organ functions as well?
The contacts are "audio keying" type so they may in fact ground unused contacts to keep noise down etc. That would likely cause problems with the new circuits but I'd need to see the schematic. I recently re-purposed a Yamaha changeover keyboard to a MIDI controller using MIDI Boutique but in my case, all old circuits were removed just using the contacts.

Geo

[sweetbb]

Hi Geo,

I have gutted the organ, and all the contacts are clean. None of the original electronics are left inside the organ, as it was beyond my ability to fix it or have it fixed. I am using a Midi Boutique console midi encoder, which uses the 8x8 diode matrix for the keys.

[geoelectro]

You should probably try to have just open and closed contacts without them resting on a common buss. You could try wiring a few and trying it but I think you would have problems with the same contact being connected to a common buss across the 8 note encoder bus. It's possible the diodes will block this but I'm not certain.

Geo

[orgfred65]

Just a general comment on key scanning. If the contacts in the organ are silver plated, then these will be less successful with a 5V signalling scheme. Gold plated contacts work perfectly at 5V. I believe it is recommended to use a slightly higher voltage with silver contacts - say 15V, for reliable operation. Silver does work perfectly when clean, but airborne contaminants can lean to some tarnish building up which will ultimately affect the electrical performance.

[sweetbb]

I have manged to remove the common bar above the contacts that I want to use.