[JohnCT]

Do you mean the bonded boards between the display and the TCON? We call them address boards although I'm not sure that is a good definition either.

Those are often symmetrical and sometimes not, depends on the whim of the manufacturer. Those that are symmetrical and have two ribbons are almost like two different screens side by side. In those, you can get half a normal picture with just one ribbon connected. If removing one side restores the picture on a TV that shows none, the disconnected side is bad. That can be a problem on the address board, or a bad COF chip on the flexible ribbon, or a COF chip on the side tabs of the display (usually hidden by the front mask).

We see a lot of newer screens that are not symmetrical at all. New Samsungs and some others have a 25 series eeprom on one side. If the main board polls the display and doesn't get back a good answer, the TV shutsdown and recycles. Many modern displays won't run with just one ribbon disconnected, either having no picture or causing a shutdown. Worse, many cheap TVs (like Black Friday toilers) combine the TCON with the display address boards, so we have to work on the "TCON" right on the display screen. Sigh..

As far as that LCD screen tester, they probably are better for laptops where computer manufacturers don't want anything to do with screen design but just pick a vendor and design their video circuits to match, so there's probably far fewer unique designs available in laptops or computer monitors. Those testers won't help where the TCON is actually part of the display.

I don't know of any professional TV techs working today that have one of those testers, although one of my friends with a computer store has one. I can't conceive of any tester possibly covering every contingency of TV panel manufacturer.

John