Service Tips:
Circuit Overview:
Uses 6 of the "synth on a chip" CEM3394 with a Z80A processor and a custom IC controlling things. Also a sequencer and arpeggiator. Velecity sensetive. Fairly typical architecture.
I've found a few problems with this one. You MUST load factory patches or after you install a new battery, no matter what you program, a weak hashy sound (probably signal bleeding through switching chips) is all you get. This thing apparently performs a check sum and if it's not valid simply ignores you until such data exists.
But that's not all. I had a bad leak of charge that drained batteries FAST on my first unit I worked on. I repaired that problem but a 260uA leak remained. At the time it didn't occur to me. I figured I'd fixed the problem. But then I got a second one and this one seemed to be fine after battery replacement. But...it had that identical 260uA leak. And I realized..wait. This is too much. When Chip Select is high (within .2V of Vnv) we should see something around tenths of a microamp/chip. Plus some for the chips that run them (74HC02 and 74HC32 plus the MC14022 which is hooked to Vnv also for what reason I do not know. The reset line of that chip..apparently so that it doesn't glitch on bootup.)
Now, it cost me a lot of pain to find the answer. If you have this problem of early battery death, I want to know about it. Call me at 406-582-5849 or email me. If you see that same current drain let me know because I'd like to establish if this is indeed a design flaw or what. My unit now draws a microamp or thereabouts. Also don't forget to reinitialize wheel, MIDI channels, etc. Search faq above for help there. And also if you power up w/out analog board attached display should count 1-4.