I've had 2 cd6's lying around for years,both skipping and not reading some disks.
I've managed to get them both going,by adjusting the FBAL and TBAL trimpots.
No special equipment was used, just known good cd and one with plenty of scratches on it(but without damage to the alu foil)
I just played back the good disk until it started skipping, then slowly adjusted one or either of the trimpots until playback resumed,
continue playback until it skips again, a very small adjustment of one of the pots makes it play smoothly again.
Once the good cd plays without skipping,move on to the scratched disk and repeat the procedure,again using minute adjustments
to make playback stable.
With a bit of luck ,and patience you're cd6 will be as good as new!
Its definitely better to leave the laser diode rf alone until you have at least tried this first.
Seeing as both my machines needed the adjustment,theres a good chance you can get youre cd6 going this way.
Good luck.