Vintage Synth Repair

I bought an Ibanez SDR-1000 reverb recently (1986-ish, designed by Sony and 
also sold as the Sony MU-R201).  There was also an SDR-1000+ which was 
evidently an upgrade version- I assumed it would be an EPROM swap, like the 
Alesis Quadraverb Plus.  I'd like to upgrade it if possible, but I opened it 
up and there's only a ROM chip soldered in (Version 1.0).  I don't imagine 
either Sony or Ibanez being any help, but I'm not really sure where to look. 
  Has anyone got any information or ideas?

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