Now, I'm by no means an expert, but the folks on this board, in fact it may have been this very thread, have told me that repairing the ASU/DSU board would run upwards of $900. So needless to say I gave up. Of course, you'd want to ascertain that this is in fact the issue first.
I used the instructions from the service manual for this TV to get to the status screen back in the days when the screen stayed on for a couple of minutes. The status screen will show any error that happened within the TV in the past. On the status screen I saw three errors marked with a 1 instead of zero. The light bulb error, the fan error and the Lower B error. All three errors happened to me on the very same day. :O

Since I had no idea what Lower B error was at that time I went searching and eventually asked about it here, and of course got my answer.

Adding insult to injury was the fact that I had to buy a brand new bulb in order to see these three errors and realize that my TV is now completely unusable. But now it has a brand new bulb in it.

HTH
Rudy