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

[Tom Wiltshire]

Hi Tim,

Does the voice do this in both filter modes? - e.g. with the 12dB filter and the 24dB filter?

If it does, that might suggest something going funny with the resonance control voltage for that voice, since the resonance is unlikely to have failed simultaneously on both filters. If it the resonance is fine on one filter but not the other, I'd expect the problem is in the actual filter circuit itself.

HTH,
Tom

On 21 Feb 2015, at 19:22, tprivitera at nc.rr.com wrote:

> Hello everyone,
> 
> I wanted to see if anyone had any ideas on an issue I am having with the resonance on one of my OB-Xa's voice cards.  With patches that have more extreme resonance settings (ie: the resonant sweep patch 'C4' aka Van Halen 1984 patch), instead of sounding "whistling" at the top of the sweep, this voice sounds "buzzy", with no whistle, if that makes sense.  That voice sounds fine in other patches without resonance or with resonance at a lower setting.  Here is what I've done so far:
> 
> - Recapped all 7 electrolytics on the card
> - Cleaned all the connections on the card and pins on the voice card motherboard that seat the card
> - Pulled every chip on the card, cleaned pins and reseated a few times
> - Swapped multiple CEM 3320 filter chips in to confirm it wasn't a bad chip
> - calibrated the card correctly.
> 
> I've calibrated this whole synth several times in the years I owned it and since it's not a calibration issue and I've hit all the usually fixes, I'm kinda stuck.  Anyone have this specific problem before or can think of what might be causing this?
> 
> Thanks in advance,
> Tim
> 
> 
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