Moog Music Forum

Hello
Don't know if you have resolved your issue. As with your problem I was also focused on the digital board for quite a while with the issue I had. Please refer to the post Moog Source. No Pitch/Oct Change Level 1. As it turned out there was a bad OTA IC that was pulling the address lines down ...

As stated in the post above the OTA IC is truly a heart and soul type of IC for analog music synthesis. In the Moog Source it is used in ten different circuits on the analog board. They are U17,U24,U29,U33,U38,U39,U42,U44,U45,U49. The following article expands on the function of the OTA IC. Credit ...

Don't know if you got the problem repaired. I can offer some help if you post the schematics. Own a Moog Source that had a similar problem and found that there was a bad OTA IC which is a comparator driven op amp. It could also simply be a normal op amp that is latched high

Issue has been resolved. Had a classic case of not being able to see out of the woods because of the trees. After exhausting the addressing theory I moved to the analog side of the equation. From U3,U4,U5 input output channels and circuits I traced to the culprit. U17, which is a 3080A OTA IC went ...

Thank you for the reply. To date U3,U4 and U5 on the analog board have been replaced. That was my first thought.
Tracing the address lines back to the digital board led me to replace U23,U24,U27,U28 as this encompasses the entire address
bus as far as i can see. Still same result. Do not like the ...

Have a difficult issue. In level 1 there are no pitch or octave changes. Appears stuck on one note.
If level 2 function is accessed for example S@H, normal pitch and octave changes occur.
As post replies filter in I will elaborate further. My personal thoughts are corrupted address
messages from ...