I suspect this unit was made somewhere 89-90 (crazy...) I was hoping for the SAJ to (As i have 4 of them), but the Dividers in the soviet synths should be some clones of the MM5824N, however I'm not quite sure of that.
I had 4 of the Dividers broken, but eventually found some similar Soviet IC that would fit with some modification.
Here is my long "Me/Myself" conversation about it:
https://groupdiy.com/index.php?topic=73443.0
The Main Oscillator was also not working so it all started out with NOTHING. No sound anywhere... I eventually found the Broken OP amp, I just put an 741 in there and it seem to work fine. All in all the thing has like 25 PCBs and i must have found about 15 broken OP-amps in there.
The thing looked like it had been spending 10 years in a cold/Wet basement here in Berlin. 25% of all the transistors were showing Oxidation on some of the legs and had no Contact. By the way, those Soviet KT315 transistors look so cool.
I recaped all the cards. And only that was like 2 days of desoldering.
After a closer look at the schematics i realised that the Ringmod card was the same as the 3 other "Tremolo" cards but with a smaller Capacitor so i just made the Tremolos "High speed" switchable, voila... 4 Ringmods!
The Sub bass part was not going through the Filter or the Chorus so i made that selectable.
the filter was always (!!?) running through the Chorus, i found that a bit stupid so i also have a switch for the filter parallel to the Chorus at the output amp.
The only mod i unsure of is a change of resistor in the Resonance feedback path in the State variable filter. Im not sure if it is possible to get more resonance that way or if i'm only changing the filter Response. (ooh... The Math..)
I haven't fine tuned it all yet but the thing sound so "Good"! Not like a Pro5 or Memory Moog good.. But like Weird/Good.
Lastly, i would not recommend anybody to take on this synth for a client as a "Repair Job" its just to crazy. But as a Project to Learn and get into Soviet IC/Schematics/Alphabet and general Fault checking skills... This is the bomb!
Sound will come
S