Will not play dvds

This question is actually for a koss dvd player, moded ks4122, it is very similar inside to the philips.

I have replaced the laser pickup and the spindle motor, out of 10 cd's, only one cd will load and play, the dvd will not even spin.

The pickup is mounted on two rails that are screwed the metal chassis, the screws go thu tension springs before they screw into the metal, is the height of the laser pickup critical, ie how loose or tight the screws are, to get the dvd to play.

Any help would be appreciated.

Update, i changed the sled motor, no change.

I used a slyvania dvd as a reference and readjusted the spindle height and the laser table height, this made the player now play approx. 4 discs, but the dvd will not load at all still. I also used a bubble level and adjusted the laser table screws to get level.

Mechanical spindle height and laser table height should be good, maybe i got a bad new laser pickup or i have a electrical problem with the mother board.

I posted pictures of the circuit board and the mech.

If any has a service manual for this unit or a unit similar, i would pay for it, i do want to get this unit working properly again.

Yes and i did remove the solder blob on the laser pcb.

Any help would be appreciated.