Your post seemed to be similar to my problem. I bought my Toshiba 57HD81 new unit in 2001 and have had NO problems until now. Picture went black, red LED blinking, still have sound. Unsuccessful hard reset. Just prior, color was fine except mildly vibrating sides picture thinking it was cable reception. Today, the tech took the board back to his shop for benchwork. He plans to replace the conv. IC and 2 caps.
So far, sunk costs $128 (Housecall-$95, Diagnostics-$33). Quoted $460 and have it back in 3-5 days ($425 plus $35 tax). Since you did a lot of research I wondered if you thought this reasonable?