There are two main problems, notes/tones being played without a key pressed on start up. the second is once key A4 (and a couple surrounding keys G#4 and A#4) is pressed, the tone keeps playing after the release. Here are my notes on what i observed happen over time.
https://www.synthxl.com/roland-vk-1/
On start up, drawbar 2’ leaks a G#4 tone, and 1’ leaks A3. 16’ leaks a very faint G# tone (same tone as 2’). after sometime being on, 2 2/3’ leak both the G# and A tone but also faint in volume.
immediately after pressing the A4 key, this tone is ‘stuck on’ being continuously played without being pressed. this tone will be played through any drawbar. same is true with G# and A#, though these dont happen on the first key press (these two keys are usually affected after being powered on for 10-15 minutes)
interestingly certain drawbars will cancel the sound of the ‘leaking’ tones but only when played. for ex 16’ turns off the A4 tone (only for that drawbar) when played, comes back after release. one more note is 2 2/3’ and 2’ produce subtle ‘pop’ on attack and release of the A4 (or other leaking tone key) also will turn off the leaking tone when pressed.
There are two suspects, im thinking its either a 4066 IC chip on the tone generator board or on the switching board. i checked these chips on the tone generator and noticed the chips for C-F were 35 and 25 on the out. F#-B had less output averaged around 27.5 and 21.5 on the outs. is this a PSU problem with chips on recieving correct Volts or the IC chips malfunctioning?
ive been trying to fix this organ for a couple years now, any input is greatly appreciated.