Adjusting The Voltage >>>

6)With the PS2 plugged in (power and video) turn it on. You are ready to adjust the voltage for the laser. Only adjust the screw for the type of disc you are having problems with. If you are having problems with both, do them one at a time.
Remember, now that the unit is on its side the CD voltage control screw is above the DVD control screw.

If at all posible use a non-metalic screwdriver, as static electricity can ruin this portion of your PS2 (a ฃ50+ part!)...

7)Turning the screw clockwise increases the voltage, counter-clockwise decreases the voltage. Because you risk of blowing the laser if you give it too much voltage, always start by decreasing voltage.
In my experience, you generally have to add voltage, but for safety, I suggest you reduce voltage first. Using a small screw-driver (non-magnetic & non-metallic if possible) turn the appropriate screw counter-clockwise two degrees. Load in the CD and wait, if you still get a disc read error move the screw another two degrees. Repeat the process...