OBXa Problem/Advice

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drawtippy
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Re: OBXa Problem/Advice

Post by drawtippy » Thu Oct 16, 2008 4:43 pm

Thanks guys,

I'm gonna actually try all of the above. Pull out the chips and clean and then pull out the board and look for loose traces/wires. My gut tells me it's the later because the board was actually functioning perfectly for a minute there until I moved it. but we'll see. As far as the J-wires, I actually made new wires and soldered them in. This was way over my head, but it seems to work. There is just one bum key now and I know how to fix it.

I hope other people are reading this thread! I am not electronically inclined but I've managed to do a lot of repairs on this myself--without taking it into the shop. The best part so far has been calibrating the pitch bend lever and octave switches. They were out of wack when I got it and now they are perfect. I'll gladly share any tips I've learned during this process. Thanks again.

P.S.-- I'm gonna post some close up pics of her when I get a chance.
Visit http://www.arttestmusic.com

Voyager, JP-6, Pro-One, 800DV, CZ-101, VL-1, Micron, Solina, OB-Xa, JX-8P, Sid Station, xoxbox

Steve Jones
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Re: OBXa Problem/Advice

Post by Steve Jones » Sun Oct 19, 2008 5:25 am

I am restoring a couple of them at the moment, they are a great example in so many ways of how not to build a reliable synthesizer. One thing to be wary of is the DIP switch pack that turns the individual voices on and off. They can get intermittent and really should be replaced. A trap is that if you switch them with your fingers that will work sometimes but not always, so you really need to use a stylus and make sure that each switch is pushed ALL the way in the ON position, as older switches sometimes will not work if they are sitting flush, they need to be pushed right down firmly. Best to replace them if you can.

Another common problem is with the non J-wire actions (the ones that use the rubber pads) is that the metal contacts become tarnished and need to be cleaned back to a bright shine with a non-abrasive solvent or cleaner, being careful not to remove the plating.

A third common problem is rectifier failure, where one of the diodes in a rectifier bridge pack fails and puts lots of ripple into the machine. I feel that these diode modules are under-rated for the OBXa.
Synthesizer service tech since 1982.
Synth parts and service, Sydney Australia.

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drawtippy
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Re: OBXa Problem/Advice

Post by drawtippy » Mon Oct 20, 2008 3:40 pm

Steve,

Thanks for the very technical addition to this thread! Yeah, I haven't even touched my dip switches, they look really shady and fragile. Of course leaving all the voices on, did make the tuning process much more of a pain. And I didn't know there were versions of the keyboard with the pads. My wires, were literally snapping at the base where they go down inside the housing-- but I did take a moment to gently clean the bus bar and make sure all the wires were hitting it cleanly. As far as the rectifier, now that's way over head. If she has a problem like that, I'm afraid I will have to finally bring her into the shop.
Visit http://www.arttestmusic.com

Voyager, JP-6, Pro-One, 800DV, CZ-101, VL-1, Micron, Solina, OB-Xa, JX-8P, Sid Station, xoxbox

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