Quote Originally Posted by keithdoxey View Post
You just need a bigger resistor instead of the 11 ohm you currently have.

With your 11 ohm resistor you have 50mA flowing through the backlight.

11 * 0.05 = 0.55V dropped across the resistor so your LED backlight has a forward voltage of 4.45 volts.

For a 12v supply you need the resistor to drop 7.55v

7.55/0.05 = 151 so 150 ohm 0.5 watt resistor for 12V supply @ 50mA

For the 18v supply you need the resistor to drop 13.55v

13.55 / 0.05 = 271 so 270 ohm 1 watt resistor 18V supply @ 50mA
having regard to RYTECH, i wonder whther 78L05 was used and if so proper termination adopted or Not?
afterall for 50mA with 12V input, the device need not be hot. let RYTECH measure the current at input 12V point and it will really speak.