Due of some request we updated this solution for quick and easy troubleshooting.
This solution may only works after ensuring and confirming that the LCD is okay or already tried replacing a new one. Also try to restore/flash update the device firmware before doing any hardware repairs on the phone. Just refer to the given solution below and locate the highlighted components on the Nokia C5-00 PCB board.
Nokia C5 Dark LCD Screen Display, White LED Light failure solution
1. Try to replace the LCD screen display module.
2. Clean the LCD pin connector if oxidized,.
3. Check/replace the two 6.8 pica farad capacitors near the pin connector.
4. Trace the positive( red line) LED supply voltage line paths to opposite terminals of the capacitors.
5. If also the keypad LED light is not working, Check the VBAT 3,8V across the inductor coil.
6. If the voltage reading is okay, check/replace the coil and the diode. If the VBAT voltage is missing, apply a jumper wire from the battery positive terminal down to the inductor coil.
7. Check the negative (green line) LED supply voltage. You check it by reading a voltage by putting the multimeter red probe to the LED positive supply voltage then to the LED's negative supply voltage. Read about 3-5V on that spots.
8. If the there is no voltage reading the possible faulty is the GAZOO IC, reworking or replacing it will only fix the problem.