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Trying to Repair a VAX77 - Keys Losing Responsiveness
Old 1 week ago
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Trying to Repair a VAX77 - Keys Losing Responsiveness

Hey, I'm a longtime user of my red VAX77, that rare MIDI controller with polyphonic aftertouch that folds in half. It's built like a tank, and I've only used it for light gigging - although it did make a trip to Belize for a wedding lol - but it still looks very good. Unfortunately, some keys have started to malfunction, and I am hoping to track down technical information to assist me doing my own repair. I contacted the Infinite Response website, they're out of the keyboard business, but I'm still hoping they still have folks around who remember the VAX77, or can direct me to someone who has some VAX77 background. But I'm also resigned to the fact I might get a Zero Response from them.

The problem I'm having is the keys near the split keyboard have begun to become less responsive, where only a very hard strike sends MIDI; lighter touches do not sound/send a MIDI Note On. Having 6-8 keys right in the center of the keyboard that don't sound fairly often is getting to be a big drag. It seems to be a proximity effect, in that i can push the key slowly to the keybed with no Note On event, and then push a bit harder, where it does send a Note On event with a velocity of 1.

I am looking for any sort of information on how the keyboard sensing works and what adjustments might be available to me, to help me understand what’s causing this. Also some information on how to disassemble the unit would be extremely helpful. I have done some basic disassembly - since the worse offending key is the middle C just to the right of the body split, I have pulled the metal inside end plate off to expose the side of the key, and note the small screw-like magnet under each key that seems to initiate the Note On event when it gets close to the board. By pushing a slight amount on the board to position it very slightly closer to the keybed underside, it definitely improves the bad responsiveness on the bad keys. That led me to think that the magnet might be adjustable on threads, but not wanting to damage anything, I have not been able to make any sort of adjustment to the magnet height with some medium twisting with a needle nose pliers - most likely I’m not even moving it - if it’s even intended to be moved.

Both halves of the keyboard are beginning to experience the problem, so I’m thinking the only way I can truly fix things requires getting the keyboard disassembled. I am a technically adept guy with a lot of tools, and I’m slowly and cautiously sorting out a good way to disassemble, but so far I have not figured out how to release a key. I am experimenting with the end Hot Key; I was successful in releasing the end metal strip spring, although I’ve been reluctant to just let it fully release, with all the sticky glue on the end, so I temporarily clamp it with a small vice grips - but the key is still locked in place, apparently at the center key pivot. I’m not completely sure whether the front metal rail needs to be removed, but I reached an impasse trying to remove it - there are 3 screws on the chassis bottom with what looks like tiny hex slots that just slip before breaking the screw free. Now I’m working on the underside small philips screws that seem to line up with the center key pivot rail, with the hope that they are related to freeing the keys.

It's a longshot, but maybe somebody out there has some come across some drawings or service manuals? And what about replacement parts - anybody know if any are stockpiled? I want to continue to be a VAX77 fan, but it’s reached the point where I can’t rely on it for live performance, so this is my last ditch effort before retiring it.

And for the record, I still have a box of VAX MIDI parts - I just can’t bear to toss it in the trash!

Thanks folks,

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