Original post by: Minho ,
There are two possible scenarios that I can see: # You possibly have a bad batch of LCD’s. You’ll want to look at this carefully in terms of batch/vendor etc. # If this is a logic board issue, then I would look at the backlight filter. This is a Ferrite Bead and the purpose of using a FB is not to act as a fuse but to filter out high frequency noise. A FB will let DC pass but filter out high frequency noise. When there is too much noise on the line it becomes resistive (whatever the spec says, i.e. 33R). Perhaps this phone has been repaired in the past and someone just jumpered the filter instead of replacing it meaning that high frequency noise is getting to the actual backlight. # Otherwise, if the screens are good then you may want to wipe the entire BL circuit and rebuild.