My Toshiba 36A50 had the same issue.
The picture would gradually shrink until it no longer appeared and there was only a thin line running from left-to-right across the center of the screen.
The volume still worked perfect.
From information I gleaned from this site and others, I removed the main circuit board and flipped it over to re-solder the pins going to the Vertical IC (TA8427K).
This IC is right about center of the board mounted on an aluminum heatsink so it is soldered in vertically.
You can easily see the part number on the IC and it is the only one of that part number.
Additionally, the silk-screen on the PC board has a QC301 next to it identifying the part.
After I re-soldered it, the TV works excellent.
I just did this yesterday afternoon 10.26.08.
Thinks to note that have been pointed out by others:
- There is high voltage in the TV even after the power is removed. There are several sites where they tell you how to remove the power.
- Make a note of all connections. Most of the connectors are keyed to go in only one way but some you can turn the connector either way. Write down all the information and take some digital pictures before you disconnect everything.
- As was pointed out but other people, the Vertical IC and/or some of the surrounding capacitors may be defective and need replacement. Its possible that your local Radio Shack may have what you need but I would not count on it. A possible source for parts is www.digikey.com.