Nokia 5800 LCD Display Backlights LED's repair
The Nokia 5800 Xpressmusic used an LED driver IC same as other Nokia mobile phones, this IC chip drive and control the current and voltage to LCD backlight LED.
Repair hints, refer to the picture above:
1. check and test the LCD backlight LED's, you can do it by setting the Multimeter to X1 just refer to the pictures above for the pin configuration. The positive (cathode) and the negative(anode) is indicated on the LCD pin connector. If the backlight LED's wont light up, a new replacement LCD is necessary.
1. Check the coils for continuity and resistors resistance value, replace if found busted or damaged. A very low resistance resistor can be easily damaged when a short circuit happens. Short circuit happens when the device is damaged by a liquid or so called water damaged handsets.
2. Check the line paths between each components, you may start from the pin connectors then between particular component parts.
3. Check the Vbat voltage across the filter coil. this voltage is the positive voltage of the battery, you can check it also by doing continuity check from the cell phone battery positive terminal to the coil.
4. Remove the LED driver IC, check both of each solder ball line paths to where it is being connected to a particular components. If all lines were okay find a new LED driver IC replacement and replace it.