LC70LE550U no pic

[paulstef]

Please someone tell me that this TV is not scrap.

Picture works great but turns off after a few seconds. Backlight stays on, sound stays on.
Replaced T-con, same problem. Apparently TCON shuts down it's output due to overcurrent/fault detection.

Removed front bezel to get access to the tab bonds / COFs. Sure enough, to the right there are two, the first and third from the bottom that heat between 50 deg C and up to 100 deg C within a matter of seconds. All the bottom COF stay at about 40 deg C, all COF on the left side stay at about 25 deg C.

The voltage on the little ceramic cap right next to the overheating COF is 5.9V.



Did anybody have this problem and find a solution or remedy? Maybe lowering some voltage that comes from the TCON/modify the circuit ect?

Why does it have an awesome picture while it's working? Why does it not always overheat to the same temperature?

I know chances a very slim to repair this but it's really a shame to scrap that TV.

[budwich]

Re: LC70LE550U no pic

IF you are good at soldering, you might try swapping out the bad smd capacitors. You can compare voltages along with resistance values with others on the board to see if this is indeed the issue. Finally, IF the operation is not successful, you can try the "last chance save" of just removing the tabs on the failing side. Lots of posts dealing with this type of save. The set will operate "near design" with a very watchable picture. A 70in tv that I saved over 2.5 years ago is still operating fine in this mode. NOTE: the tab removal can not be reverse so it is the "last straw operation"... so exhaust all other avenues before taking this last step.

[paulstef]

Re: LC70LE550U no pic

IF you are good at soldering, you might try swapping out the bad smd capacitors. You can compare voltages along with resistance values with others on the board to see if this is indeed the issue. Finally, IF the operation is not successful, you can try the "last chance save" of just removing the tabs on the failing side. Lots of posts dealing with this type of save. The set will operate "near design" with a very watchable picture. A 70in tv that I saved over 2.5 years ago is still operating fine in this mode. NOTE: the tab removal can not be reverse so it is the "last straw operation"... so exhaust all other avenues before taking this last step.

Yes I'm very good with soldering but there are no shorted or low resuistance ceramic caps anywhere.

Why does removing the apparently defective tabs work? I think I have to read up on how they panel actually works. :-D

[budwich]

Re: LC70LE550U no pic

its quite possible like most things... complete failure is only "one state". As you have found, the "compromised tabs" appear to be drawing more than "designed" levels of current which kicks in protections.... that's good as it is possible (as in vizio implementations with little / no protection) to save other components and ultimately reduce damage.

Anyways, you indicate that your picture is fine when it works. I would suggest that you input a known diagnostic pattern (color bars or equivalent) and closely look at the result. It may show some "warning signs".

Further, I gave voltage / resistance checks but those were to provide a direction... of course, there are others especially with capacitors and that capacitance checks along with esr checks.

As for your question on tab removal working... do some reading. For my part it works and that's all I need to know as there are lots of things in life that work and I don't need to know why, just that it works. :-)

[paulstef]

Re: LC70LE550U no pic

WOW!!!

I can confirm this worked!

I don't know for how long but this is incredible, remove defective parts and it works again, like you cut out a cancer.

If all repairs were like this!! Like, ok, TV doesn't turn on, remove the PSU, hahaha.
Now if I don't break anything when reassembling I'll have a really nice TV, can't really sell it in good faith...

Thanks

If it doesn't hold up I'll update this thread

[freakaftr8]

Re: LC70LE550U no pic

Looks good nice save! I've sold a few like this after removing the side tabs however I do tell the buyer about the problem and usually sell cheap.

[budwich]

Re: LC70LE550U no pic

no confirming is need... the forum already has "tons" of posts that confirmed that. Glad you didn't toss it out. Happy viewing.

[paulstef]

Re: LC70LE550U no pic

Anyway, I want to thank you both.

So these circuits must be redundant then. I wonder if this would work on other smaller panels too, I have several of them laying around...

[freakaftr8]

Re: LC70LE550U no pic

Yes they should work on any panel that uses gate drivers on each side. One is essentially a send and one is a receive more or less. When you remove 1 side the sending side must receive at the same time.

Of course there is a lot of other technical data that goes along with this but this is the most easiest way to explain how it works to the best of my knowledge. A lot of it has to do with frame rate reproduction and horizontal data driving signals