oh I've done all that Fizzy (more than once.. ...tbh I don't want to keep manhandling the cart and headshell too much, I just know one false move and I'll bust it and that'll be another £150 down the bloody drain!).. the trouble is that one of the demodulators doesn't separate the Front Left + Rear Left at all.. while the other demodulator separates them like a good'un but with distortion in the Rear Left only (like big blasts of distortion!).. otherwise I would indeed say yes it must be the stylus/cart.. ah well.. it was working great on Tony Orlando and his Dawn chorus tonight.. then I try Bob Dylan's Wavey Planets again and BLAM..! Revenge of the Distorto-tron..!
Short of that solution I have no more.
Time to take em both out in a nearby field, attach some C4 and blow em to ' ell.
But.....first replace em witha cheaper outboard unit (Sansui, or Pansonic, et al -all had cheap CD-4 units).bugger JVC !