[sdiy] Ideas on resonance problem on single OB-Xa voice

[tprivitera at nc.rr.com]

I fixed it - bad (drifted) resistor. This one won't be destroyed by incompetent repair jobs, I can assure you.  I'm careful and have been able to fix every issue I've had with in the 8 years I've owned it and learned a lot in the process. From a power supply rebuild, logic chip replacement, full calibration, to keyboard rebushing/leveling, etc.  Never botched once (maybe I'm lucky?).  My OB-Xa works perfectly, sounds amazing and is rock solid (no random lock-ups).

I should have been more clear in that I was having trouble with this particular schematic.  It didn't seem clear to me, based on what I was seeing on the card after I pulled it out.  

Tim

-----Original Message-----
From: Michael E Caloroso [mailto:mec.forumreader at gmail.com] 
Sent: Saturday, February 21, 2015 6:21 PM
To: tprivitera at nc.rr.com
Cc: tom at electricdruid.net; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Ideas on resonance problem on single OB-Xa voice

> I'm not that good at reading schematics.

Please do not try to fix this yourself.  Stop right now and take it to a competent repair tech.  Too many of these wonderful vintage synthesizers have been destroyed by incompetent repair jobs and repair techs are starting to refuse botched DIY repair jobs.  A repair job like this is seldom trivial and cannot be fixed over the internet.  If you cannot grasp complex systems such as polyphonic analog synths or correctly interpret a schematic, you will do more damage and your repair bill will be higher.  The circuits have many complex interactions.  A problem can be deceptive and may actually have another cause somewhere else.  Complex systems need complex tools.  A DMM is going to tell you little.  Oscilloscopes and other test instruments are not easy tools to use and it is easy to use them the wrong way.  "Professional driver" disclaimer...

There's a reason these things are labeled NO USER SERVICEABLE PARTS INSIDE.

MC