Bumping this question back to the top.
The power light flashes green three times, separated by a long pause, then repeats. Set will not power-up. I'm wondering if the repair involves board replacement or just a component. The user manual vaguely says the green LED blinks at 3 second intervals because the CableCard fan has stopped. Mine blinks 3 times at three second intervals, the set never powers-up, and all that is running is the CableCard fan. I disconnect the tach wire, the 12 volt power to the fan will cease. Thus, it is sending tach pulses, and appears normal on a scope. Three green flashes from the power light, in an endless sequence that doesn't change when I disable the fan. Turning- off the TV by the power button does nothing because the set never turns-on.