The laser current is controlled by the DVD drive CPU. It reads the value on the pot but it's not the only thing used by it to define the real current that go to the pot. There's also some information on the PS2 eeprom about the laser and it's that plus the pots that define the laser power.
About the laser coils, it's position is critical. I never remove the metalic pad on the laser. I remove the black screw in the middle of the plastic holder of the lens assembly and change only that. You should be careful at the time of tightening the screw to don't put weight on the mechanism. If you do it will bend and the lens will lose it's position. So changing lens is hard. A missaligned drive might read CDs and not DVDs so not all the time the lasers are blown. Crank up the pots is not a real solution.
SCPH-10000_GH-001 SCPH-15000_GH-003 SCPH-18000_GH-008 SCPH-30001_GH-005 SCPH-30000_GH-016(V4) SCPH-30001_GH-010(V4)
2xSCPH-10190, 2xSCPH-10350, 2xSCPH-10280
"**** j0 hackers!"
-Sjeep (As seen on TOXIC OS ELF...)