Early MIDI synth with some scaled back aspects but a lot of typical subtractive analog things going on of course. Timer chips used for the DCO design as was typical in the first generation of those units. Analog VCF and VCA chips but digitally generated envelope controls and oscillators. BBD based chorus
The MKS-30 has the failure prone filters of course. I've had good results with soaking them in acetone for several days then peeling off the resin coating. Crystals tend to form that are conductive under that jacket and it just all washes away when you perform this procedure. Otherwise I've only done key cleanings and pot replacements and so on with JX-3P that I can recall.
I have a variety of parts that might help you on these as it appears Roland used many of the same parts those years. And also there are some discrete components that I usually stock.
Contact Sound Doctorin'
GOOD NEWS for MKS-30 users!!!! I've purchased and tested one of the 40 euro module redesigns. GREAT WORK! This should drive the price of the used modules down since these are way more reliable and sound identical! Here is the Module Retro page. This device must be hard wired which takes a few minutes but well worth the effort to get something in using common 13700 ota's.