follow the connector from the inverter to psu and check on the plug.most lcd psu's will output a number of supplies.these could be 3.3v,5v,12v,15v,24v.If you have backlight the 24v is probably ok,if not you need to check it's reaching the panel from the psu.If it reaches the panel but still no backlight then look for circuit protectors on the inverter.You don't need a schematic,just follow the cables/print
