Problem with a 50004

[madmax4]

i have knowledge on electronics but i'm not a ps2 specialist!
i use "ultimate ps2 repair guide" and i can see some pictures on how to measure the laser signal with an osciloscope.However, the book doesn't include SCPH-5000x versions so i don't know where to measure.Anything that you suggest and covers SCPH-50004?
i want to try all the possible solutions before i change any parts. i.e:laser beam or mod chip.(i supposed that one of these is fault).
But i need some suggestions.
i have also change the angle of laser head to make it totally horizontal(it wasn't) .is it right? any way on how to adjust the angle of laser rather than doing it in blind?