I am looking at the CD player part of an Aiwa CX-N500Z (NSX-500), many times does not focus when a disk is loaded, but retrying sometimes starts and plays the disk perfectly all the way.
I have swapped the entire optical pickup assy from an identical working unit and the problem is in the drive electronics, not the pickup. Both pickups work fine one one unit and both fail the same way in the other. Mostly Sony parts, pickup: KSS-210A, ICs: CXA1081A, CXA1082BQ, CXD1167Q, BA6296FP.
I have scoped some signals, when it its trying to focus the FOCUS-OK signal from CXA1081A activates momentarily but nothing happens, this should trigger the servos and start of spindle motor. Sometimes the focus locks and disk starts to spin and suddently loses focus for no obvious reason. However while playing it does not lose focus easily, buttons FF or REW behave fine, but jumping tracks sometimes cause it to lose focus.
A secondary sympthom (maybe related) is when playback is stopped through the stop button, the sled returns home and at the end the sled gears slip some teeth because the inertia, the motor does not brake in time. BUT if playback is stopped with the stand-by button instead, it does the same without teeth slippage, because it brakes. I ran some tests shorting the switch contacts and with the Stop button the sled moves some extra millimeters due to inertia. I can't explain how the BA6296FP can stop the motor without brake as its MUTE signal is wired to Vcc.