Reads CDs like a charm but not DVDs

Here goes
I got a V9 from a guy that was droped on the floor like a couple of times or something (or once REALLY hard) :crazy:

anyway i got the pieces and started putting it back toghter

the tray is busted and there seam 2 be parts missing but enought beating around the bush

here's the real problem:
after i got it back toghter (after soldering a few cables and so on) i got a almost working ps2 :D

i put the first disc i found in it and tryed it out (not caring what it was at all) happend 2 b a audio disc and booted without any problems what so ever

next i tryed a dvd the lasers seams 2 b focusing but it cant get it right (the laser prob works cuz i can actually see it switching on and off evem moving around)
iv tried diff types of media original games movies backups nothing works it just makes clicking sounds for a while then stops anyone know what could b wrong and/or what could fix this?

(every type o cd works ps2,ps1,audio, backup audio all those i can test without a chip installed)

i should ad that i actaully see the laser lighting up and going off so the laser diod should b ok (from what i know i should b able 2 see a red laser when its trying 2 read a dvd and so i do, and cd laser if outside of the spectrum the human eye can see)