PT54DL50 (by 2 users)

There is a problem in your 3.3v main line and until corrected it will not power the lamp. This isn't usually an expensive repair but one that a shop will need to do since most of the work will be in trace testing voltage and signal using a scope.
For future information only here are the blink codes for this unit:

1 | Load Shortage
2 | Over Volage
3 | Fan Sos
4 | Main 3.3v
5 | Lamp Disable
6 | Gc3fm-Iic
7 | Gc3fs-Iic
8 | Gc3i-Iic
9 | Color Wheel Stop
Hope this helps!
Bill