Samsung UE55MU6120K Boot loop with backlight no video

[handsworth]

Re: Samsung UE55MU6120K Boot loop with backlight no video

Here I give you a photo of each half (left and right cable) where to isolate the CKV. Maybe it will be easier for you.

I have 2 of these MU models and your placements worked for me. Definitefly bad screens. Was hoping to light it up and verify the main boards still worked. Cudos to you

[Davi.p]

Re: Samsung UE55MU6120K Boot loop with backlight no video

not on the cof, on the panel distribution boards , a jumper on the diodes if present

[hugmax]

Re: Samsung UE55MU6120K Boot loop with backlight no video

check diodes on the panel small boards, maybe try shorting clk lines to gnd one by one, if a new set of black lines appears step to the other clock, until no new lines appears, that clock line is probably connected to a bad diode to be removed.

Short the clock lines on the COF?

Because I couldnt find the clkv points on the cof.

[Davi.p]

Re: Samsung UE55MU6120K Boot loop with backlight no video

check diodes on the panel small boards, maybe try shorting clk lines to gnd one by one, if a new set of black lines appears step to the other clock, until no new lines appears, that clock line is probably connected to a bad diode to be removed.

[hugmax]

Re: Samsung UE55MU6120K Boot loop with backlight no video

I just went on try and error, uncover some lines on the flex.
from 12-20 went down to 16-20 if I left any of these lines free the TV goes on reboot frenzy.
but the best I got the TV is this.

Is this the best? Can I do something to get a better picture?
br

[Davi.p]

Re: Samsung UE55MU6120K Boot loop with backlight no video

I think no, the thin circuits within the glass some times belongs to a sufficient overload and so the tcon protection, sometimes the short belongs to an intermittent faulty line.. depends which mosfet in which circuit position is been hit by the spike..maybe the faulty line is due to an half broken fet connection and not a short..
last but not least, i have a dvbt2 Panasonic with lines starting from both sides.. sometimes the image works with few lines, sometimes it starts scrambling lines in big part of screen.. depends on thermal state..

if someone don't wants to drive crazy, it's sad but these screens must be disposed of..

[lotas]

Re: Samsung UE55MU6120K Boot loop with backlight no video

hugmax this is probably due to the fact that both the sides are broken..

If there were two sides broken, there would be no picture at all and the TV would always reboot.

[Davi.p]

Re: Samsung UE55MU6120K Boot loop with backlight no video

hugmax this is probably due to the fact that both the sides are broken..

[hugmax]

Re: Samsung UE55MU6120K Boot loop with backlight no video

My update for my TV: I did the jumper T-RDY1 and T-RDY3 in #36 and I found that the short was on the left and I isolated the ckv (12-20).
but I got some lines on the screen, how many lines should I uncover?

I cut the jumper after I got image on the TV

I uploaded the video

https://imgur.com/6rGvALj

[fanaticgames]

Re: Samsung UE55MU6120K Boot loop with backlight no video

Hi Fanatic, as per Lotas post #113, try connect the screen, don't forget there is a serial connection between mb and screen due to the spi flash on it, so it's normal maybe a reboot, another test that can be made is try booting the tv, if it reboots many times freezing the spi flash, if tv works ok desoldering the spi, freezing it 5sec before reading it with programmer then let it come to ambient temp then rewrite it, solder back then try..

the tv works now both cold and hot, even tried to flex the motherboard

[Davi.p]

Re: Samsung UE55MU6120K Boot loop with backlight no video

Hi Fanatic, as per Lotas post #113, try connect the screen, don't forget there is a serial connection between mb and screen due to the spi flash on it, so it's normal maybe a reboot, another test that can be made is try booting the tv, if it reboots many times freezing the spi flash, if tv works ok desoldering the spi, freezing it 5sec before reading it with programmer then let it come to ambient temp then rewrite it, solder back then try..

[nomoresonys]

Re: Samsung UE55MU6120K Boot loop with backlight no video

we are all here to learn something and lend a hand to solve problems for this I update the situation at every step

I for 1 certainly appreciate your efforts in that.

[fanaticgames]

Re: Samsung UE55MU6120K Boot loop with backlight no video

After reading the whole 7 page of the post, because I have the EXACT same problem, I did the masking and all and I haven't fixed yet.
BUT I did buy a motherboard from Ebay. And had the same reboot loop when both flex where in.
It seems that I have some testing to do on Monday when I get to my shop.

As soon as you do some tests let us know

[fanaticgames]

Re: Samsung UE55MU6120K Boot loop with backlight no video

After post #5 even I thought it might be the panel because thats a classic symptom of a panel issue, just goes to show, always keep an open mind when troubleshooting and be careful not to jump to conclusions, which we all do sometimes.

we are all here to learn something and lend a hand to solve problems for this I update the situation at every step

[hugmax]

Re: Samsung UE55MU6120K Boot loop with backlight no video

After reading the whole 7 page of the post, because I have the EXACT same problem, I did the masking and all and I haven't fixed yet.
BUT I did buy a motherboard from Ebay. And had the same reboot loop when both flex where in.
It seems that I have some testing to do on Monday when I get to my shop.

[nomoresonys]

Re: Samsung UE55MU6120K Boot loop with backlight no video

After post #5 even I thought it might be the panel because thats a classic symptom of a panel issue, just goes to show, always keep an open mind when troubleshooting and be careful not to jump to conclusions, which we all do sometimes.

[nomoresonys]

Re: Samsung UE55MU6120K Boot loop with backlight no video

I'm just now realizing that a stupid little solder crack is probably the same problem I had with a sony a while back.

[nomoresonys]

Re: Samsung UE55MU6120K Boot loop with backlight no video

Yes, I noticed you got it right in post #101.

[fanaticgames]

Re: Samsung UE55MU6120K Boot loop with backlight no video

Yes, dc to dc converter, somehow I put it in wrong and came up with this, didn't think that seemed right, lol: https://www.aliexpress.com/i/3256803...apt=4itemAdapt

as I had already hypothesized a bad weld it was the attachment to the wall that didn't make it work anymore because it worked 30 hours without any problem without moving it, anyway let's see, at worst I change the motherboard, the important thing is not to have thrown away the TV due to an alleged defect in the display

[nomoresonys]

Re: Samsung UE55MU6120K Boot loop with backlight no video

Post #98 and #102 was close, I bet when you had it going for 30 hours it wasn't exactly straight like when its on the wall, like just leaning on a bit of an angle and making that joint work.