[lcaillo]

I would be looking for a bad connection between boards or something similar.

 

[lcaillo]

It does not appear to have a convergence problem. Looks like something from the internal test pattern generator getting into the video somehow. This is not likely a DIY project.

I would still be looking for a bad connection, bad ground, wire dress problem or something similar.

 

[lcaillo]

Power supplies with problems in the filtering can contribute all kinds of symptoms like this in any type of set, so that is a possibility. Best to check the obvious first, then to be sure you would need to look at the supply lines with a scope.

 

[lcaillo]

Not sure. I was under the impression that shorting the pins was the procedure to do to be able to operate the set with the back open, not to restore it. I have never had to restore a lost digital function, but what I have heard is that you have to jump through hoops with JVC to get the parts.

 

[lcaillo]

The technician is supposed to come back tonight to look at the issue, I have 10 pages of posts of what can happen if the back is removed while powered on, do you think covering the hole with tape, replacing the back and powering up the tv will reset the dvi?

Ten pages of posts are not relevant. He, or you, need to talk to JVC and get the real information on the matter. If he is not a JVC ASC that may be difficult, but they should at least be able to refer you to someone who can answer your question definitively.

 

[lcaillo]

I was able to find a service bulletin on the DVI problem. While I do not generally do research on individual problems nor post service bulletins, this affects lots of people and the so called "booby trap" on the JVC sets is so irresponsible, IMO, that I think it is appropriate to post the info publicly.

The service bulletin is in a sticky here:

http://www.hometheatershack.com/forums/jvc/17982-no-dvi-video.html

 

[lcaillo]

I remember I read somewhere else that there's an EPROM for this DVI. There's a round optical hole on top of the EPROM. When TV is on and light goes through the hole to EPROM, the EPROM will be ERASED. There used to be a lot of these kind of EPROMs for MCU. JVC will be your last resort to get it programmed or get a pre-programmed part.

What someone really should do is to take off the back cover while TV is powered off, and use something like black electrical tape to cover that hole up before powering up the TV again.

IIRC there is simply a photodiode that changes a setting in the EEPROM in these (if activated while the set is plugged in), not an old style UV erasable EPROM. Note the difference in the acronym. There is no schematic data on the digital input board, however, so it is hard to be sure exactly what they are doing, but most techs routinely cover it or just don't fire the set up with the back cover open.