no picture backlight works LN55b650 samsung

[dacdd]

Hey guys. Had this for about 2 and a half years with 0 issues. So I am watching tv then all of the sudden random vertical colored lines showed up on the left hand side of the tv and the right side while having no defects was noticabley dimmer then the left.



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Not knowing what to do, I unplugged the tv for a few hours. Upon plugging it back in, there was no picture at all. The backlight stayed on, and the sound worked as I blindly switched around inputs.

I googled the issue extensively and almost everyone fixed theirs with a t-con board. I ordered one and installed it and nothing changed.

Basically upon installing the new tcon I did notice a faint "electrical type smell" if you know what I mean.

I contacted a tech at shopjimmy.com and he suspected the main board.

From my research, I have obtained the following information. There is an LVDS cable that connects the main board and t-con together. You can essestainlly wiggle this cable in and out of the t-con while looking for flashing or activity on your screen. If you get anything your t-con should be ok. I performed this test and got no response, however, if I powered the TV off and disconnected the cable, I got an even backlight response when turning it back on with the cable disconnected.

If I turn the tv off, then connect the cable and turn the tv back on, I get the backlight however I also can see a faint vertical black bar about 13 inches wide towards the left side of the screen (is that what they call LCD banding?), which almost makes me think the t-con is doing something.

I am pretty clueless on TV repair, I am really hoping to get this TV back to life, and am wondering what kind of tests I can do or if the gurus here would suspect main board. Im not very knowelgeable with a meter, however my dad has been an engineer for honeywell for 35 years and is very good with circuit board and using a meter.

I really do appreciate the help

[Dgtech]

Re: no picture backlight works LN55b650 samsung

I'm wondering if the Tconn board is still the issue. You replaced it with another one and smelled an electrical type of burning smell with the same resulting picture. I think maybe something blew out the new Tconn board in the same area that the old one was blown. Just a wild guess.

Post a clear picture of both new and old Tconn boards. I'd like to see if anything on there is toasted.

[dacdd]

Re: no picture backlight works LN55b650 samsung

Hi DGtech. I really appreciate your response.

After reading your comment, I looked over every square inch of both t-cons board.

Low and behold, the New t-con board indeed had burn marks on it, which would certainly explain the smell. I have attached pics of the spot for reference.

I carefully examined both boards everywhere, the old t con looked absolutely perfect, while the new one obviously did not. I attached pics of both the t-cons and the burn area. Doubt the actual board pics will do you any good cause my cell phone cam apparently sucks, but you can at least see the burned up part on the new board.

If you would like better pics of the t-cons I could get my dads real camera and post them tomorrow, however I assure you I did inspect both boards rigoursly and only found that one issue on the new board.

THe pic of the new t-con is the one that has the ribbon cables plugged in

[tom66]

Re: no picture backlight works LN55b650 samsung

Looks like the gamma control IC has failed. Did the people you buy it from give a warranty on it?

[dacdd]

Re: no picture backlight works LN55b650 samsung

Hi tom. I got it from shop jimmy. I believe they have a 180 day warranty. Do you think the board was bad from the get go or something else caused it to burn out?

[tom66]

Re: no picture backlight works LN55b650 samsung

Unless your old board has the same damage, I reckon the board you got was faulty already. They are pulls from cracked screen TVs so who knows what has happened to them. The TV it was pulled from could have been dropped and this could have damaged something.

[Dgtech]

Re: no picture backlight works LN55b650 samsung

I googled the issue extensively and almost everyone fixed theirs with a t-con board. I ordered one and installed it and nothing changed.

Basically upon installing the new tcon I did notice a faint "electrical type smell" if you know what I mean.

Based on what was already done, I'd bet that the original board has the same failure since it produced the same outcome. Please post pics of the original board as well to verify.

Now... If this is the case, this is going to take some investigating to fix this. My first thought would be that the vcc to this chip may be too high. To find out which pin is VCC, you would need to know what that chip's numbers are and since the chip is burned, it's gonna be hard to see the chip's numbers and orientation.

The problem may still be from the mainboard. It dishes out the power and signals to this t-conn board.

[dacdd]

Re: no picture backlight works LN55b650 samsung

I have attached a pic of the original boards IC. The same IC that burnt out on the second board shows no evidence of being burnt at all on the original board. I cant find any evidence of burning on the first board.

The numbers on top of the IC chip read 178H68A P9178MQ

Other symptoms: If i hook up the old T con all i see is the tv's backlight.

If I hook up the new tcon I see the backlight and a darker vertical band about 13 inches wide more towards the left side of the tv (not sure if this info means anything)