I am repairing an old analog synthesizer (Siel Kiwi) with a missing CPU and the CPU board in a bad state.
I can't get such a CPU in the right package anymore, so I'm writing an emulator for it which will run on a more modern, much faster MPU. That alone replaces the CPU, RAM, and ROM. The remaining stuff on the board is lots of I/O both analog and digital which I'm planning to replace with something more modern, like a DAC with 32 channels instead of the many chips and opamp sample-hold circuits that are on the original board.
I can't get such a CPU in the right package anymore, so I'm writing an emulator for it which will run on a more modern, much faster MPU. That alone replaces the CPU, RAM, and ROM. The remaining stuff on the board is lots of I/O both analog and digital which I'm planning to replace with something more modern, like a DAC with 32 channels instead of the many chips and opamp sample-hold circuits that are on the original board.