PLEASE HELP !!

I have a Sony WEGA plasma KE-P42XS1 and I entered the test mode by
pressing the keys on the remote: {display} - [5] - {up vol} - {TV}.
(The intent was to fix a problem with the horizontal position of the
picture, but I never got that far.)

I got some big characters with Tnnn on the upper right. The last thing
I did was hit the sequence {display} - [5] - {DN vol} - {TV} and
nothing happened. I decided to stop everything and power down the TV
and power up. I was horrified to discover that the TV would not
initialise. I only had one power light and no other lights (stdby was
off). I disconnected the power to the TV, waited a few minutes,
reconnected power and tried to turn it on, but all I got was the one
glowing power LED as before. TV was dark. No other LEDs were on. Remote
did and does nothing to the TV (remote itself is working). I even
cycled the power switch on the right side of the set with no results
other than the power led cycling on and off as I pressed the power
switch on and off.

My TV is not under warranty. I am an electronics technician and I have
the service manual, but it says nothing about the service codes. I got
that info from another forum. Now I know why the service manual said
nothing about the codes.

I figure that the next thing I can try is perform a firmware or
software update, but I need the firmware file and the instructions or
service bulletin that goes with it.

Can anyone help me ? (short of suggesting to take it to an authorized
Sony service center)

Please advise.