Another Ob-Xa Issue

Jacob Hunt · Post by **Jacob Hunt** » Thu Sep 26, 2013 7:32 am

Everything's going great until.. The top voice boards start to become horribly distorted. Autotune becomes useless. Somebody help me. Is this likely an OTA issue, or something more?

Jacob Hunt · Post by **Jacob Hunt** » Thu Sep 26, 2013 8:11 pm

Turns out the bottom boards also start to get crazy after the 3rd B key. They're not distorted badly like the top ones, but they sure don't sound right at all. Thanks in advance to anybody who may have some insight.

Jacob Hunt · Post by **Jacob Hunt** » Thu Sep 26, 2013 10:57 pm

It seems it is related to key CV maybe. Those notes' boards that go wacky are not getting past 3 volts for the key CV input when I go higher up the keyboard. Strangely though the top boards are getting proper voltage up until past 4 volts. The schematic has key cv as coming out of a 4051 (U47) on the lower board and running through a series of op-amps, which are simply just not in existance.. Maybe there's something after it that is the problem.

Jacob Hunt · Post by **Jacob Hunt** » Fri Sep 27, 2013 6:37 pm

Common sense prevailed, and I checked the voltage verification steps. IC #145 (another 4051) on the upper board is not recieving a proper 5.6v, but a not so healthy 2v. Now to track down the culprit(s).

Jacob Hunt · Post by **Jacob Hunt** » Fri Sep 27, 2013 8:12 pm

Turns out it was the 4051 itself. duh. Glad that's over with, I was getting pretty scared.

radek tymecki · Post by **radek tymecki** » Fri Sep 27, 2013 9:58 pm

4051 is common failure in ob-xa. try to track down simple modification coz 5.6v is not proper voltage. i mean it is but it's factory mistake

Another Ob-Xa Issue

Another Ob-Xa Issue

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