Fixing a DX7-II . . . volume on one key

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BluMunk
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Fixing a DX7-II . . . volume on one key

Post by BluMunk » Sun Nov 20, 2011 4:57 pm

Instead of selling my DX7-II for parts, I decided I ought to plunge in and try to fix it myself. After all, it was just a bunch of keys that were off their springs and such.

So, I opened it up, re-seated the keys, and had to buy one replacement key.

Well, the replacement is in and works fine, but that one note now plays at a much lower velocity than any of the others. Any suggestions? Is this something that just needs some cleaning? If so, where and how do I clean it? I don't want to ruin any contact points/electronics.

Also, as an aside: man was it tough to get at the action. So many screws . . . next time I do something like this I am going to make a drawing and label each screw so I can put each one back exactly where I found it!

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Re: Fixing a DX7-II . . . volume on one key

Post by rhino » Sun Nov 20, 2011 5:43 pm

Here's a VERY basic overview:

Under each key is a switch with three metal leaves. The key moves the middle one down when you press it. When the key is up, the moving middle leaf touches the upper leaf. When you press the key, the middle leaf moves down - leaving the upper leaf - and touches the lower leaf. When you get to the contacts, look at the ones on either side of the bad one and CAREFULY adjust (by bending) the bad set of three to match the others. Note that the upper leaf presses down on the middle one when the key is off... that means as the middle moves down, the upper will 'follow' it...staying in contact for a fraction of a inch. Either the upper leaf is bent too far down, or the bottom leaf is bent down.
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Re: Fixing a DX7-II . . . volume on one key

Post by spacefolklore » Sun Nov 20, 2011 6:08 pm

Does it work well when velocity sensitivity is disabled? I had a problem with random keys in the lowest octave on my DX7 MkI - they output lower velocity than the rest. The contacts looked good so I reflowed all solder joints on the keyboard PCB and that completely revitalised it.

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