Janko chromatone repair?

[Joseph Austin]

I have a Chromatone CT-312 (Janko) keyboard 

http://chromatone.jp/index.html
that has developed a problem.
The symptom is that certain notes either won't consistently sound when the corresponding key is struck, or they sound at maximum volume regardless of touch.
I suspect the cause is a misalignment between the key and two switches that engage when the key is pressed. One of the switches causes the key to sound, the other I surmise is designed to close a fraction sooner or later and thus is used to measure the the speed of the strike.

The attached photos shows the mechanics. 

 The two black "buttons" on the right side of the frame engage switches on the circuit board below. You can see the profile of one key to the right--the bottom surface of the key engages the switches.

The key is hinged with a flexible strap attaching the back of the key to the back of the frame (multiple hinges are formed together 
I suspect perhaps the frame or board warped or the hinge deformed somewhat.  I had been able to get the notes to sound properly by variously shimming the hinge, twisting the key, or tapping the black buttons with a pencil, but I can't get such tinkering to result in a stable fix.

I suspect that this is a fundamental design flaw, but I'm wondering whether anyone has ideas for fixing it.
Alternatively, if someone would be interested in trying to fix it,
or using it for parts, contact me privately and we might work out a deal.

[Aaron Andrew Hunt]

On Jul 30, 2016, at 8:45 PM, Joseph Austin <drtec...@gmail.com> wrote:
> The symptom is that certain notes either won't consistently sound when the corresponding key is struck, or they sound at maximum volume regardless of touch.

This is normally resolved by cleaning the contacts with electronic spray cleaner like https://www.amazon.com/CRC-5103-Quick-Electronic-Cleaner/dp/B000BXOGNI

You'll have to take the whole keyboard apart, lift up all the silicon plungers, spray them and wipe them with Q-tips to clear away any debris. Most of them will look clean but they aren't; oxidation is usually invisible, sometimes looks like a dull film. A small particle of dust is often the culprit for non-playing keys or keys that play only at one dynamic level. It seems impossible, but dust can creep in over time when keys are played hard.

Good luck!
Aaron

[Ian van Loyden]

Hi, Joe

I assume that the angle the bottom of the key hit both black switches causes the problem. I faced the same problem with 3D printed keys, although my Red Wholetone has just one switch (possibly with two triggers inside, have no idea). The solution would be to wrap a relatively thick sticky tape to the bottom of the key at the proper place so that it fills any possible gaps between it and the black switches. One layer, or two... depends on the key.

Sometimes the actual switche can dip in itself like same happens with computer keyboard rubber switches. The solutin would be to slightly bang them with finger or rub them till they release and go back to normal state.

Thats my suggestions so far.

[Ian van Loyden]

Yes, the other more techy solution could be the reason Aaron explained above - dirty surfaces of the contacts. This will take you much more time and hassle cause it is laborous to dissamble the keyboard to PCD boards and bits and pieces.

[Joseph Austin]

Thanks.

Disassembly is especially difficult the way the Chromatone is assembled.

One can't just remove one key at a time, since several key hinges are formed as a single piece.  

But I'd suspect oxidation, or perhaps something got spilled into the keyboard,

because the problem seems to "creep" from one key to neighboring keys over time.

Joe

On Jul 30, 2016, at 3:08 PM, Ian van Loyden <adxo...@gmail.com> wrote:

Yes, the other more techy solution could be the reason Aaron explained above - dirty surfaces of the contacts. This will take you much more time and hassle cause it is laborous to dissamble the keyboard to PCD boards and bits and pieces.

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[Joseph Austin]

Thanks, I'll try that.
Joe

[Andrew Wagner]

Does the chromatone use keyswitches or just the electronics from the
synth it was based on? If the former, maybe you can learn something
from user reports for the original keyboard...