My 42PFL5603 is also showing a similar problem. The circular central area of the LCD is very dim and it becomes brighter towards the corners. There also appears to be a flicker and hum coming from the DPS-279CP and after a few seconds the TV shuts off and reboots.
I have checked DPS-279CP solder quality, aluminium electrolitics, HV caps, mosfets, flybacks, etc... but nothing obvious.
Reading the post is sounds like the master/slave boards might be at fault and that a mod is required to both boards. Is this mod to prevent damage of these boards or to fix a defect that may occur after a while?
Mod (I) is a 33V TVS zener and mod (II) adds a 4R7 and cap. Without the schematic I would speculate these mods are to prevent/dampen "LC tank" ringing on the master/slave inverter IC supplies which would occur when the DSP-279 shuts off due to stray inductance in the wires joining the boards and the near zero ESR of high value input filter ceramics. If this is true my master/slave inverter ICs may have been damaged and applying the mod will do nothing. Maybe someone can confirm?
Cheers
