Grabbed an old CS1 in the basement and found that Q1 and Q2 were missing on board.
I've got services note on google but not sure which fet is related to Q1 and Q2.
Any help would be appreciated :)
I wonder why they were missing. Not likely to fail.
They are just switches, not "tone". I would try "any" N-type JFET. Figure out which hole is Gate. The other two pins S and D may go in either hole (interchangeable in this use).
Turned out that my CS-1 is the older revision so Q1 and Q2 are not FET but transistors.
Everything is running fine now thanks !