Yesterday evening we replaced the CR2032 battery in my YS-200. The diagnostic mode showed it as only being at .4 volts, and I was getting the usual gibberish for patch names in the user bank (even when loaded with sysex) and tuning issues. We followed the instructions from http://snackeyes.blogspot.com/2017/06/replacing-yamaha-ys200-synthesizer.html
except we made a battery holder, attached it to the underside of the card reader, and ran wires to the metal pieces we left attached. When we turned the unit on after reassembling it, the diagnostic said the battery was at 4.6 volts, "NG" (No Good). It wants somewhere around 3.5 volts I think. That's what the battery was labeled too. I did a factory reset, and the user bank retained the factory preset duplicates fine. And I was able to record a track on the sequencer which I could not do before. I turned the YS200 on this morning, and it was out of tune again, and the patches were all gibberish in the user bank once again.
Yamaha: Motif XF8, YS200, CVP-305, CLP-130, YPG-235, PSR-295, PSS-470
Korg: Krome 61
Kimball: Broadway (R-80), Valencia III (S-20)
Western Cottage Organ Co. reed organ
Accordions: Titano Virtuoso Converter, Borsini Vienna 723, others