Sequential Circuits Pro One Keyboard Not Functioning

Hello Everyone,

I was given a Sequential Circuits Pro One a while back. Recently the keyboard section has stopped working. Whenever I press a key, I get a cruddy noise sort of sound if the oscillators are set to follow "kybd". In other words, the gate seems to be working but whatever communicates the pitch of the key pressed to the oscillators is messed up.

From the research I have done, it seems the 8021 keyboard processor might be the culprit. Apparently this part is pretty hard to find, if not impossible (wine country is sold out). I can't find a datasheet of this part, so I can't figure out how to test it.

If anyone has experience with these synths and could offer some advice for testing, or what my next move should be if the 8021 is toast I would very much appreciate it.

Thanks,

Tim

I don't have any experience fixing or troubleshooting a Pro One, just playing one. But, anyway... Do the gate/CV inputs work? Does it play if you plug in an analog sequencer, for example. If so and you still can't get the keyboard functioning properly, adding a MIDI input might be a good fall-back.
http://www.synhouse.com/midijack.html
That's actually a decent mod for a Pro One even if the keyboard is working. :wink:

Good luck!
~ Charlie

Thanks Charlie,

I think some kind of midi>cv is the best way to go at this point. The CV input does work. I would love to have a fully-functioning instrument, but I think it may be impossible or very costly.

I'm checking out the PAiA Midi>CV kit.

http://www.paia.com/proddetail.asp?prod=9700K&cat=12%22

My studio partner has a modular that I'd like to control as well, and the paia seems to be able to control more than one synth.

Tim

well definitely open it up!

the keys are attatched to the main board by a single 16dip ribbon connector that just sticks into a socket. Its very possible for it to get loose, or even fall out. Make sure its in there!

secondly, the best place to get parts for the Pro One is through synthesis technology - the dude who makes the MOTM synths. He usually has a nice stash of CEM, SEM, and parts that Sequential used.

Another thing to consider is whether you have the J-wire or membrane keyboard. If you have the J-wire, its pretty easy to clean the key bus and make sure everything is making good solid contact. If you have the membrane, you are more prone for complete failure.

Remember Occams Razor - its most likely the most simple thing that has gone wrong. Esp with the Pro One - its a very simple synth, and it was built really well. I have had a few of them, and its only been the most minor things that makes them crap out. Lost my LFO once - and after replcing a 3340, I realized that there was simply an open resistor in circuit. Now I have an extra 3340

anyway, open it up, do some cleaning, and report back!