About 2 years ago the tv started shutting off intermittently. If was well out of warranty and seemed to operate fine when powered off and restarted. Over the next 18 months the issue began to happen more frequently until finally about 6 months ago it stopped turning back on. It would start to power up and the would shut down with the 3 flashing LED's on the front console.
I started trouble shooting the problem in this order:
1) checked the back door switch for proper alignment --> result: properly aligned and no change in symptoms
2) checked that the power cord was seated properly --> result: properly seated and no change in symptoms
3) ordered new lamp and replaced lamp --> result: new lamp did not change the symptoms
4) at the same time I ordered the lamp, I ordered a new color wheel because I could hear a problem with it --> result: new color wheel is not noisy anymore, but no change in shut off symptoms
5) inspected and cleaned fans to confirm function --> result: fans in good operating condition and no change in symptoms
6) called professional repair person to look at tv --> result: he confirmed that both of my lamps were good and also swapped in a good ballast with no change in symptoms so my lamp and ballast are good. He also visually inspected the power source and board and said that he didn't really see any issues there and suggested that the next step was replacing the light engine.
OK, I sent the repair man away thinking that the symptoms don't match a light engine issue

Disclaimer: I'm not a professional TV repairman nor do I play one on said TV, but I'm reasonably handy with a screwdriver -- in other words, I may be in way over my head on this
Thanks in advance!