In Nokia 6760s there are six white LED bulbs used and mounted on the keypad matrix, both driven by an LED driver IC mounted near and besides the SIM card slot or holder.
Each white LED bulbs have individual voltage supply line paths but all both came from the LED driver IC.
Hints in troubleshooting keypad backlight failure on Nokia 6760 slide:
If all the white LED bulbs doesn't turns ON, check the VBAT voltage (battery voltage) across the inductor coil. Check the coil's resistance or continuity if the voltage is missing. If the voltage reading is okay, try to rework the LED driver IC. Replace if necessary.