Model LTF550HQ03 TV will not turn on but can hear crackling noise.

I have read other responses for the above problem with Samsung TV but have found no bad capactors or anything that looks burnt or damaged. Vacuumed the interior the first time this happened and it came back on again for about 4 weeks and the problem returned again . Removed the back again everything looked okay but this time I tried heating the main circuit board BN94-02696G with a hair dryer until warm and tried turning on TV and it came on again. Been working ever since. Boards are unavailable for this what would cause this? Any suggestions of what it could be? Any help would be appreciated. Thank you Bill