Vintage Synth Repair

Hi all.

I was given a Roland U-20 that seems to have some keyboard problems. A
lot of the keys don't sound at all, or are at half volume. If you
knock the keyboard, or the stand even, sometime you the key will start
to sound. To me, it sound like there is corrosion or something on the
contacts. Is this something that I remedy myself? I am hoping that the
mechanical aspects of the Roland keyboards are close enough to others
that someone can answer me.

I took the bottom off the keyboard but that is as far as I have
gotten, as of yet I cannot see how to remove the actual key assembly.
I have a Korg DW8000 that had 2 keys malfunctioning and I was able to
get that working, I am hoping that this will be repairable by me also.

I hooked it up to another keyboard via MIDI and all worked great, so
pretty much the keys are muckered up.  The only other problems I have
found is the bank 6 button does not respond and when I try to access
PCM cards, it can't find them.  Have to wait to see if this is a card
problem or more bad contacts.

Thanks all

Thanks for your help