friend has a really rare synth (synergy) and we wanna repair

>>1155645
>could i apply a +/- voltage to the power pins, touch a wire to one of the pins and measure resistance? i think that'd tell me if it runs current or not.
no. that's not how digital circuitry works.

>>1155653
that's what i assumed. still a novice to this stuff. do you know of a way i could test it?

generally speaking if you cant work out a road map by yourself you won't be able to do the logic/work

Since you have documents, you can create a testbed for each chip. Most will probably be simple, input through some data bus and output on another bus or an analog signal. If you don't know microcontroller design and digital data bus usage it will probably be too hard.

>>1155683 thank you! i'll try this out. we do have a really big resource of information (schematics, manuals, programing, etc)

>>1155645
Check all the PCB tracks to see if they conduct, a common point of failure is near any jacks. This is the quickest thing to check so I'd do that before testing components.