In troubleshooting this problem you may need to try to replace the LCD screen first to easily confirm if the LED light bulb is already damaged or not. If the said newly installed LCD still shows a dark screen display and the LED failed to light up, this solution below will show us the next step to proceed in fixing this problem.
Nokia X3-02 Display Light Problem Solution Guide
Repair hints for Nokia X3-02 Display light Problem:
The SMD transistor LED driver components shown on the solution above holds both for the positive supply voltage(LED+) of the LCD screen display and keypads, while the negative supply voltage(LED-) is directly feeds from the PEARL IC.
If the said transistor is damaged it will result to both and display and keypad back lights failure. So, check and replace it first if such problem occurred.
If the said transistor confirmed okay, the next step is by checking the 3.7V battery voltage(VBAT) across the inductor coil and diode near the PEARLJ IC. Check or replace also these components.
Lastly if the above procedures didn't work, reheating, reworkin and possibly replacing the PEARL IC will only solve the Nokia X3-02 display light problem.