Need help to fix an old SH2000 Roland

Hi all,

First post here! Nice to meet you all. A good friend of mine gave me his SH2000 Roland for fixing it.
There’s 2 different problems with it.

First, when using, all sounds that have a sustain state (I mean all sounds that won’t die if you keep the key pressed). When I play then release a note then the first key of the keyboard will be triggered without I touch it. If I play a C then release the key then the lowest F (first key) will then trig.
I’ve been checking the connections of the keyboard and nothing seems wrong to me. I’ve also searched for any bad connection on ALL the connectors.
I’ve test ALL the diodes and find one that was faulty in the ADSR2. I changed it but I’m not 100% the one I’ve used is a possible equivalent.
My second problem is that I have a high pitched sound that is always preset on all sound even on bass sounds. Not too loud but quite annoying!
IS there anyone here that could help me investigate? I know a little in electronics. I’ve already made a lot of stompboxes and fix many machines but here I’m stuck.
If you can’t help me maybe you can tell me where on the net I should ask my questions.
All the best!