Vintage Synth Repair

Hello:
I'm trying to solve a problem with an old KN800 from Technics.
The owner left it stored for aboiut two years.
When he turned it on there's no message in the display and the keyboard produced no sound.
The internal memory is keep with a capacitor 1 Farad 5,5 Volt in place of the normal litium battery.
I replaced the capacitor, gave it a charge for several hours.
Now the keyboard starts up with the regular message on the display but seem that the memory is all scrambled with strange messages in the display and the sound is kind of random.
My questions are:
- Does anyone have deal with a similar problem?
- Does anyone have a pdf version of the service manual?
- Does anyone know how to make a hard reset to the machine?

Any help will be appreciated.
Best regards.
José.
Portugal