Korg 800DV Synthesizer Repair Service. This synthesizer had problems with the repeat modes. These didn't work as they should. It was able to quickly find out that it was just a contact problem in the rotary switch. These could be eliminated quickly with a good cleaning.
With a synthesizer of this age and with the problems described, one can confidently assume that there are other problems. Because something like that always sounds to me as if the last service was a little further back, or the synthesizer has never had a service since it was released. In this case everything should be cleaned better. The other switches, the faders, the keyboard, the sockets ... I also quickly discovered other problems: Matsushita Elkos. These should be replaced immediately.