The digital to analog circuits are in the upper right corner of that picture. The transistors, caps and 8 legged op-amps would be suspects.
Try this link instead to the manual. And it was very slow to download for me.
http://tinyurl.com/FB01ManualEdit: Looking through the schematics C2 and C3 catch my attention as 47uf/16v non polar dielectric capacitors. Regular caps fading after 20 years, non-polars even faster.
Plaz
