Yamaha DX7 - issue with key

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Doug
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Yamaha DX7 - issue with key

Post by Doug » Sun Jun 07, 2020 1:17 am

Hi folks.

Was using my Yamaha DX7 and playing fine until a piano key (E below Middle C) acted up.

Basically when you press that key it doesn’t play the note until the key is released, and then it plays. Also with some patches when you press that key, the note continues to play after the key is released, and doesn’t fade out.

All other keys are perfect. Hoping simple key replacement will solve this, or even some alteration to the key itself. It’s not broken and feels fine when it’s pressed.

Thanks!

mellotron
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Re: Yamaha DX7 - issue with key

Post by mellotron » Tue Apr 06, 2021 4:11 am

Hi Doug,

I am new to this forum recently, and see this one post from you last June. Did you ever get the issue resolved?

I just tore my new-to-me DX7 open for the same issue as you. While I have not solved the problem yet, I think I see what is the problem. Some time in the past 35 years, a beverage was spilled between the keys. There is rust on the bottom of the synth, and on a couple screw heads under the keyboard.

Each key produces a sound by way of changing the way three different "leaf springs" interact with each other.

1) With a key at rest, the center leaf is in the UP position, making contact with the top leaf. This results in a signal telling the synth to make no sound. Let's call this CONTACT A. (Not a note, just the first condition.)

2) When a key is pressed, it lowers the center leaf, moving it down and away from the top leaf, thereby breaking the "off" circuit. Let's call this CONTACT B. As it travels down further, it makes contact with the bottom leaf. Let's call this contact C. This results in a signal telling the synth to make a sound. Presumably, the time difference between CONTACT B and CONTACT C determines the velocity (the harder you hit the key, the shorter the time between contacts B and C, so it plays louder).

With my keyboard, some of these leaf springs have visible green corrosion. I am going to try to gently burnish these leaf springs and try again. Hope this helps you move forward.
Corrosion 2.jpg

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