Does unplugging half the T-Con really prove bad panel?

[Truncatedhose]

In general, when you have an LCD with backlight but no video and you can unplug half the T-CON going into the panel and then you get that SAME HALF of the screen that you just unplugged in white with black smeary shadow creeping away from the center of the screen and the other half of the screen is still just blank, what does this really prove? It does the same thing with either half of the T-CON unplugged. Does this mean a bad panel? I thought it would show video on the opposite half that you unplug...? But it's still just blank. I don't want to jump to a bad panel conclusion without certainty. This is on an LG37LG50, by the way. Will provide pictures if you want, but my question really applies to this same scenario that I've seen on many models with same symptoms.

Help! Thanks!

[Truncatedhose]

Re: Does unplugging half the T-Con really prove bad panel?

Bump

[tom66]

Re: Does unplugging half the T-Con really prove bad panel?

If you get half a good picture with one half unplugged usually it means there is a short on one side of the panel (i.e. bad panel.)

If you get a distorted image, it's hard to tell, as sometimes you could be missing some signals by removing that connector.

[budm]

Re: Does unplugging half the T-Con really prove bad panel?

if you get half a good picture with one half unplugged usually it means there is a short on one side of the panel (i.e. Bad panel.)

if you get a distorted image, it's hard to tell, as sometimes you could be missing some signals by removing that connector.

+1

[freakaftr8]

Re: Does unplugging half the T-Con really prove bad panel?

I would say possibly not. Its rare that a bad panel would not show anything on either side. Sounds more like a tcon issue possibly. Are you getting voltages to the tcon?

but Tom is right on a part of his post where he mentioned that if you unplug one cable you could have an issue on the other side as well as some panels use a jumper ribbon in series between both halves of the top driver boards on the panel itself and therefore no you will not receive a proper picture on either side as they both have to coincide with each other to jive with the signal generated coming from the tcon board

[Truncatedhose]

Re: Does unplugging half the T-Con really prove bad panel?

Thank you Tom and Freakaftr8. I am getting voltage to the T-Con (13.0v approx) and the fuse is GOOD, but the chips and things on the T-CON never get even warm. I agree, I think it may be the T-CON. Thank you again! I will order one and let you know!

[Truncatedhose]

Re: Does unplugging half the T-Con really prove bad panel?

Well, I got one T-CON a few days ago and with it I still got the blank raster on one side, but now I had distorted, orange lines running vertically on parts of the left side. I checked my cables and connections and all was good. I sent the T-CON back for another one and with the 2nd one installed, I got the same symptom as originally: just a blank screen (backlights running, but no video). I guess either the panel is bad or it's the Main board.

Can anyone help me solve this one? Maybe someone can tell me exactly how to scope the video signal from the Main board? I have a scope (Tektronix TDS 210), but haven't used it in a while and never was the expert with scopes.

Thanks!

[Truncatedhose]

Re: Does unplugging half the T-Con really prove bad panel?

Someone, please? Thank you!

[tom66]

Re: Does unplugging half the T-Con really prove bad panel?

Yes, you can use a scope to check LVDS. A TDS210 is a little limited, in this respect an analog scope would be better (because the update rate and graduation on the Tek is very limited) but it might be possible to make use of it as a basic test.

[Truncatedhose]

Re: Does unplugging half the T-Con really prove bad panel?

Yes, you can use a scope to check LVDS. A TDS210 is a little limited, in this respect an analog scope would be better (because the update rate and graduation on the Tek is very limited) but it might be possible to make use of it as a basic test.

Thanks, Tom. Do you need me to take some pictures of the boards and plugs (what area specifically?) and also, could you help me make sure I have the scope set up correctly and walk me through this?

[tom66]

Re: Does unplugging half the T-Con really prove bad panel?

Yes, a picture of the LVDS connector on the board (showing traces) will help, also one of the probe and scope. I think I've used a TDS210 before but a long time ago.

[Truncatedhose]

Re: Does unplugging half the T-Con really prove bad panel?

Well, good news! I had a Main board on the way for this (just in case that was the problem) and I just got it in and that fixed it! So it was the Main board after all. Thanks, Tom for being prepared to help and so kind!

[tom66]

Re: Does unplugging half the T-Con really prove bad panel?

Nice to hear. You can use this as a learning opportunity to check the LVDS signals with your scope as you know the main board is working.

[Truncatedhose]

Re: Does unplugging half the T-Con really prove bad panel?

Ahh, yes, thank you, I should have done that, but I already wrapped it all up.