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Hi everyone!
I'm excited to join this group. It seems there is a wealth of knowledge here about this great instrument!
I thought it best to tackle one issue at a time instead of one big post. Long story short, I fixed the open traces caused by battery damage (battery had already been replaced) and replaced IC31 and that fixed most issues. I can now store patches and most of the erratic behaviour is gone. However, the VCA mode switch and attenuator don't work. At first, the VCA was always controlled by the EG, then after a couple reboots it seems to be stuck in gate mode. Seems like a problem with the logic circuits. After reading a previous thread in this group, I checked the effects board for damage and it looks clean (the effects don't work, but I'm tackling issues one at a time, as it's likely the same thing could be causing both problems). It seems like the control signals for VCA mode/attenuator travel on D02 and D03, and make their way through the same logic chips that reside near the "battery of death". Maybe there are PCB traces that I missed? I checked for continuity and used jumpers to fix the open traces. Is it possible that a logic chip could be partially dead? Also, am I correct in thinking the VCA mode would be stored as a binary value and the attenuator as a control voltage? I'm not sure how all these parameters are stored, are CVs all passed to an ADC and stored as 8bit values in ram? In Manual Mode, is the same logic circuitry used, simply ignoring values in ram? I've looked over the schematics and signal flow diagram but I'm still trying to wrap my head around the way the analog and digital circuits work with each other. I have a basic understanding of logic circuits and analog circuits from college, but I'm in over my head here....
Anyway, sorry for the barrage of questions but I'd really appreciate some insight here. I have a DVM and a scope is on its way. Thanks a lot for reading!
Cheers
Joel