heya! "What I do see when the power is plugged in is blocks on row 1 and 3 (it's a 20x4 LCD)" That´s ok!  ;) "In the techsheet for the LCD it says that the max voltage for the backlight is 4,8, and the typical voltage for the BL is 4,5. I measure 5,12 " It must be ok.Is a little diference.Are you sure that the + and-  conections of BL are ok?Maybe are reversed? Or maybe that can help http://www.midibox.org/cgi-bin/yabb/YaBB.cgi?board=troubleshooting;action=display;num=1061099622