The Nokia X3-02 numeric keys are mounted or attached on a flex board. So you must see to it and check the flex board assembly for possible damaged. Then refer to the solution below for it shows which certain components needs to check and replace in fixing the keypad LED failure problem.
Nokia X3-02 Touch and Type Keypad Backlight Jumper Tracks
Hints in troubleshooting keypad LED light failure problem:
1. Check the keypad matrix flex assembly, clean it if oxidized. replace the whole flex board if severely damaged.
2. Check each of the white LED light bulbs using a multimeter set to X1.
3. Check and trace the positive (LED+) and negative (LED-) supply voltage.
3. The negative supply(LED-) of the keypad LED is feed from the PEARLJ IC.
4. The components such as the transistors, inductor coil and diode will only be check if also the Display backlight LED failed or show a dark screen. The display light problem solution is here.