This repair solution can be used to solve Keypad LED backlights problem on Nokia 5730 xpressmusic.
In Nokia 5730 there are two LED driver IC that controls the voltage and current to the keypads LED backlight. The first LED driver on the left side controls and managed the four LED's on the keypads while the other one the right side holds and control only two LED's.
Check the LED backlight first before doing anything further.
If the four LED's on left is not working, you may check or replace the left side LED driver IC, same also when the two LED's on the right stop working you may check also the LED driver IC on the right side.
Just analyze and observe carefully how the LED backlight driver IC works.
Check the connection of the LED driver IC's ball terminals, including which signal or which particular line it is being connected with.Check the power supply voltage, which is connected direct to the battery VBAT voltage range range 3.7 volts. Trace and check all the lines, then apply jumper wire when found cut or open.