Fix Lcd and keypad led light problem using diagrams in which all related components are traced and marked. Troubleshoot the problem if yo want solve display or keypad backlight problem. After disassemble your nokia lumia 900 check Motherboard if there is any carbon or rust due to water damage or wash motherboard with electronics cleaner and apply normal heat with heatgun to dry motherboard. Make sure your Nokia Lumia 900 lcd not damage and also check lcd connector, some time connector damage due to water or other reason, then we can solve this problem by changing mobile lcd only. Here some diagrams are uploded to show jumpers, follow diagram instructions carefully to fix the issue.
Backligt led drive diagram
These diagrams can be used for nokia lumia 900 only, do not try these diagrams on other mobiles. If your problem not solved you can contact us for further info.