I got slightly bored and took a look, this seems to be the steps...
Go into service mode as described below.
Do not mess with ANY settings and do so at your own risk!!!
SERVICE MODE
With the TV OFF using the Sony remote press the following keys in this order 1 at a time and within 2 seconds:
- Press DISPLAY
- Press 5
- Press Volume UP
- Press Power ON
Now:
Select diagnostics.
There will be 3 sets of numbers near the bottom. The first is hours of operation and the last is panel hours.
This information was posted by others from the AVS thread linked above.