So as I supposed that there is just a little data on the Winback DVD, that is on the inner part of the disk that can be read more easily, and that is the reason why it boots. If anything boots (CD and DVD) then there is no any serious problem with the board itself (so changing any "chip" is not really needed ... :D) but the problem is the lens and/or the adjustment. You can check the things you could try before investing into a new laser:
hxxp://www.cyber-mag.com/station/ go to the laser repair section and check
1, white cog setting (remember to mark the original position)
2, azimut setting (mark the original setting)
3, laser pot values
4, laser type
if that is a V4, you have a Sony 400B laser, if it is needed to be replaced get the 400C that is much much better.