Roland SH 2000 repair

Hi , I got this SH 2000 few years ago , changed capacitors on power supply first day , was working fine until yesterday, now I have lower output volume and a high pitch sound(not very loud) beside the actual note every time I press any key, looks like everything working, switches sliders keys, just low volume and that additional high pitch noise
Let me know if anyone has an idea what is the problem
Thanks