I performed this repair, and like Alan, also got this thumping noise when I turned on the set. I searched on Google and found that this is called "Power Supply Overcurrent Shutdown."
Quoted from the site:
"Power Supply Overcurrent Shutdown means the set has found a problem in one of the circuits in the tv and shuts the tv off and keeps it off. the most common circuit in your model to do this is the convergence circuit."
Perhaps there's a loose connection somewhere, Alan? I'm going to try re-soldering in the morning, hopefully this will fix the problem.