What´s up with my laser-unit ?

First I used a USB-Mod. It did it´s job pretty good. But after a few days, it was annoying to switch this thing on-and-off-and-on-and-off.... I know what some might people think about me....but I wanted a Neo2.2, I chipped my PS2 because it´s more comfortable. Then, after installing my Neo2.2, I had to calibrate my Laser because the rotation of my drive was pretty fast, and some copies didn´t work. After calibration my copies ran better than ever before, no hang-ups, no helicopter-like sound out of my PS2...but now I can´t boot ANY DVD. No game, no movie.
So I uninstalled my Neo2.2 and plugged back my USB-Mod. Now I have a PS2 which uses an external neokey and can´t run DVD´s, because it doesn´t fix my problem.
To calibrate my laser I just used the left pot (if your memory-card-slots face towards you, upside down)
What have I done ? I tried to turn this pot into the former position, but still my DVD´s are no bootable. Unfortunately I have no oscilloscope to check the right ohms.
What I don´t understand is, why are my DVD´s affected, I think the LEFT pot calibrates the CD-Read-quality and the RIGHT is to adjust my DVD´s ?

I hope there´s just one brain which has an enlightment...

Please don´t tell me that I was stupid to install my NEO2.2 although my USB-Mod worked good......I know I was, but what if everyone would be satisfied with his current situation ? kinda boring