The Playstation 2 is a precise gaming console. Fixing the console yourself should not be done unless completely necessary. You may also risk electric shock, so do anything within your power to remain safe while attempting these repairs.
If you can, use an anti-static wrist band to ground yourself. This device is available at any electronics store (e.g. Radio Shack.)These repairs require opening the case, which WILL void your warranty. If your console is still under warranty think twice about cracking the seal.
Adjusting the laser's voltage requires some precision, being too rough can cause damage which you will not be able to fix. Be very careful when doing this process!!! Be prepared to pay Sony over $120 to fix this part if you damage it!!!
Always attempt the laser CLEANING before trying to adjust the voltage!!!!!!