Thanks for replying Wilba. Just to make sure I soldered a pot between B+ and the anode pin for the backlight on the lcd. When powered on, I slowly decreased te resistance on the pot until my volt-meter indicated 4,2V, which is the voltage needed to power the backlight according to the data-sheet (measured between Vss and LCD anode pin). I then measured the resistance on the pot and it was about 12 Ohm. That means that a 13 Ohm resistor (which I calculated) should be okay, shouldn't it?