Hi Al,
Try holding the buttons for 20 seconds and see if the letter K appears. As far as I know, this only works if the TV has faulty CCFLs, which may not be your case. I believe others have used PR- and VOL- to achieve some result, but I've never tried this myself.
In case of failure, I'd check to see if STBY-5V remains steady, and if PS-ON is present when the TV reverts to standby. If not, I'd tend to think Main is faulty, and I'd try tying PS-ON to STBY-5V via a 100 ohm resistor to see if the psu volts come up.
Also, if there's a AC-DET pin on the PSU-to-Main connector, this should come up to around 4V. This is detected by the Main micro and if it is missing, the TV wont turn on. It is generated from the mains volts on the PSU.
See how you go with that. Bruce