How I cleaned MIDI contacts.

[pentaprism]

Disclaimer: Im no accordion expert/technician by any stretch of imagination. I was wrong before and I will definitely wrong be again. Dont trust me. Do this at your own risk.

I recently bought a used Fisitalia. I didnt look for an accordion with MIDI but the accordion came fitted with a Master M95D. The seller was nice enough to throw in a Roland RA-30. Im not sure if I will be using it, but its fun.

One of the issues the seller disclosed to me was MIDI contacts need to be cleaned. At the time I didnt know what that meant. But to me MIDI was just the icing on the cake so I didnt question him.

When I tried MIDI, I came to realize what the seller had told me. When I hit a button (in MIDI of course), there might be no sound, or one, two, three sounds. When I released the button, there might be one or two additional sounds. It was not usable. The problem was only on the treble side. The bass side was OK.

So I opened the grill to take a look inside. This was the very first time I saw an acoustic accordion with MIDI added on. It looked pretty intimidating:

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I finally figured out how it worked: each rod connecting the pallet with the corresponding button now has a coiled wire attached. When the button is pushed down, this wire is raised, making contact with a rod and completing an electrical circuit. The MIDI system then knows what note is hit and sends the appropriate signal out.

In the following photo, the wire (arrow) is being raised and making contact with the rod:

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So the problem was that the contact surfaces of the wire and the rod had been corroded. The contact was thus not clean. I would need to clean the contact surfaces.

My first attempt was to use a solvent (electronic contact cleaner) to clean the wires and the rods. This didnt completely fix the problem.

So I had to resort to mechanical means: using small strips of 600-grit sandpaper, I cleaned the contact surfaces on the rod and on the wire. You can see the strip of sandpaper in this photo. I cleaned one surface, then flipped the sandpaper over to clean the other.

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It took a bit of time and patience. But now the accordion MIDI makes clean and articulate sounds.

 

[Glenn]

Looks like the obvious solution for the hand man.
Congratulations.
Is the MIDI interface touch sensitive, namely if you press faster on the button/key the note can be modulated (normally louder)?

 

[pentaprism]

Thanks, Glenn.

Is the MIDI interface touch sensitive, namely if you press faster on the button/key the note can be modulated (normally louder)?

The MIDI interface can be touch sensitive. But not in this case; the contact either makes or breaks.
It would be too complicated to add touch sensitivity feature to an acoustic accordion. You would need a velocity sensor for each note.

 

[Glenn]

I guess then you would have to go to a Roland solution.

 

[Buttons]

I have never seen inside one and it seems an interesting mix of simple electrical engineering and more sophisticated electronics. The copper rod is in effect a buzz bar to carry a mix of loads, and each connection is set with a capacitor (I think) to give the graded electrical circuit all connected to a simple set of printed straight line circuits. The connection made via a coil spring obviously works although you would think some form of copper strip would be the first soultion but this must be better or at least more 'fool proof'. Perhaps more 'spring' than a strip which would need stops. I am impressed and I dont know anythng about it. I am sure that emery cloth was thought to be better method of rubbing points...from my car days, as sandpaper may give off dust. Someone else may remember which it is and correct me.....but it has worked for you. Dirty points may stem from the connections sitting together over time. The slightest smear of vasaline may help on the ponit of connection . I would be interested in proper informed answers from someone who knows. Best wishes to you and most interesting.

 

[Russ]

Great Post and excellent pictures.

 

[Jim the box]

Pentaprism I would say that the grade of sandpaper that you appear to be using is too rough.
1). you are going to wear away the copper too much and in effect because of the coarseness you will get slightly less contact area.
2). fine particles of copper are going to get into your reeds (picture 3) and I know what mere dust can do.

May I suggest dampening some very fine wet and dry and cleaning off any residue with clean lint free cloth? I use a fibreglass stick (electricians commutator stick) on my midi.