So I recently acquired a 60 inch Sharp LCD TV with CCFL back lighting for free which has a symptom common to the model of the top half of the screen flickering. The back light in this area actually flickers. It takes around 10 hours at the moment of being left on before this occurs.
The unit has 24 tubes divided in to 4 banks of 6 bulbs each. So in this case the top 6 bulbs flicker after 10 hours of use. It has a total of 48 transformers (24 on each side)
Evidence has been found on an interconnect wire of excessive current. One wire has clear heat damage. It's one of two wires that feed the same circuit.
Heat appears to be the trigger for this issue, however I'm a bit puzzled as to what component would go for 10 hours and then start to act up. The only capacitors in the circuit path which failed are ceramics that act as a DC block, as in the transformers are capacitive coupled. Could one or more of the high voltage transformers be dropping in resistance due to a short or just basic resistance drop due to heat ? Could it be one or more of the ceramics? This is not a one off failure, many have reported the exact same issue with this model. It's just a normal failure type, no smoke and flames.
So what's a common failure mode for a back light inverter ?
Thanks,
Jeff