I had this issue with a recent job, replaced the power supply, but the connector to the logic board was not connected all the way in. So i got it all put back together and then had to take it apart again to reconnect that plug. Then it worked fine but I still have an issue with the screen. The user has it on full brightness all the time which is not normal, I think that may have caused an issue with the power supply, and the left side is darker now and I have seen all kinds of fixes for that, however I think the backlight is just bad. Good Luck.