[sdiy] Help with an OB-X issue

[tprivitera at nc.rr.com]

Hi,

2 of my OB-X voice cards have an issue with patches that have high resonance (ex: Tom Sawyer sweep) . The envelopes abruptly “shut off” in mid-sweep with a thump.  Almost like the VCA Sustain cuts off.  This is not something I’ve been able to “calibrate out” and I’ve tried swapping 3310’s and also swapped the cards around and confirmed it’s a card issue (problem follows the card, not the slot).  If I lower the control panel resonance setting enough, I can get it stop cutting out.  Filter on all other patches sounds normal, just an issue with hi-res stuff.  Any ideas or experience with a similar issue?

Also, the noise quit working.  The LEDs light with I hit the Half/Full buttons, but no noise on any of the cards.  Anyone have experience with the MM5837 chips from China on eBay?  Can seem to easily locate an NOS version.

Any help steering me in the right direction would be much appreciated.

Thanks,
Tim