Hello!
I got a CD 3300 on eBay for 10€ because I needed some Philips parts. It was supposed to be hopelessly dead.
What if...?
Fault n°1: the pickup mechanism wasn't working at all (no motors, no focus) and the dreaded question mark was appearing.
Repair: the power relay had a bad contact and wasn't supplying any voltage to the servo. Fixed.
Fault n°2: after cleaning the relay, the motor was spinning very fast and nothing else happened. Question mark again. The focus seemed to work.
This was only due to a bad solder on a cap (22MF top left of main PCB).
Now everything works, I can even read all my so-so CD-Rs without any problems! Great sound.
Conclusion: never give up on these machines, they want to live on!