Repair Solton SM-100 Synthesizer

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Repair Solton SM-100 Synthesizer

A friend brought me this vintage, digital/analog synthesizer, Solton SM100 for repair. Besides the cosmetic condition was not the best, but ok, it had mailfunction or it was completely not working. Since it was corroded all over the place due to moisture (I was happy the battery was ok at this time) I decided to look for dirty contacts first. But cleaning all contacts, changing a lot of ICs sockets (which is always a good idea when contacts are corroded that way) was not successful. Meanwhile I measured the psu, which was ok. But I decided to recap it, since this is the heart and its in use now for decades. I scoped around and found two faulty 74LS377N which are resonsible for the voice triggering. I verified these with my Chiptester and voila, the synth came back to life. I did some more recap (out of tolerance,bad esr, bad D-factor). I cleaned up the mess someone did before. Cleaned the switches and potentiometers. It took me some time but my friend is happy now;)