Samsung 4K led model UE50NU7445U no picture

[Diah]

Re: Samsung 4K led model UE50NU7445U no picture

Going for Diah's advice blocking only 3 pins made the bootloop come back.
Explanation:
Blocking all blue markings - set is OK
Blocking only the red markings - Set goes into bootloop
Now extend blocking to cover a few of the CKV lines aswell. Stay tuned.

ASG_MON_R_MB4 with its respose STV_MP4 they are only 2 not 3

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

There is only one signal which causes bootloop and that is pin 81 CKV3_MB4, but isolating only that one gives lines in the screen.
I did not investigate how many signals that was necessary to get rid of the lines, so I simply isolated the original 12 which I by luck happened to do at my first try.

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

ASG_MON_R_MB4 with its respose STV_MP4 they are only 2 not 3

Yes I know but I had to use a quite thick isolatingtape so it was three in total, but the third was not used according to pinout.

[kevinallein]

Re: Samsung 4K led model UE50NU7445U no picture

Here is the same connector but from the NU Series Service Manual

[kevinallein]

Re: Samsung 4K led model UE50NU7445U no picture

And here is the Service Manual for the NU Series

[kevinallein]

Re: Samsung 4K led model UE50NU7445U no picture

Sorry, I guess I pressed to quickly

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

Thanks.
But HOW on earth can the picture be OK while loosing 12 of the signals?

[Diah]

Re: Samsung 4K led model UE50NU7445U no picture

pin 81 CKV3_MB4, but isolating only that one gives lines in the screen.

where are the line appearing on the screen?

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

The lines were all over the left side of the screen "right buffer", black lines.

[Diah]

Re: Samsung 4K led model UE50NU7445U no picture

Yes I know but I had to use a quite thick isolatingtape so it was three in total, but the third was not used according to pinout.

regards to the manual of NU there are no SG_MON_R_MB4 with its repose STV_MP4 lol.. we were swimming out side the pool

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

regards to the manual of NU there are no SG_MON_R_MB4 with its repose STV_MP4 lol.. we were swimming out side the pool

Yes, but the question remains - how can the picture work without the correct amount of clock signals ?

[kevinallein]

Re: Samsung 4K led model UE50NU7445U no picture

I have tried to read up quite a lot over the last days. Apparently in modern panels the actual gate driver Transistors are integrated into the panel itself on the left and the right side. The external control turns on the gates line by line.

In case of a short on one side (e.g. left) that gate signal does not work correctly. However if you block the clocks on one side, the gate still opens on the other side (e.g. right). This might lead to timing violations visible in small bad lines, but at least the panel works again.

[kevinallein]

Re: Samsung 4K led model UE50NU7445U no picture

There is only one signal which causes bootloop and that is pin 81 CKV3_MB4, but isolating only that one gives lines in the screen.
I did not investigate how many signals that was necessary to get rid of the lines, so I simply isolated the original 12 which I by luck happened to do at my first try.

Just to double check: You did block two pins, CKV3_MB4 and CKVB3_MB4 and still had lines ?

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

I have tried to read up quite a lot over the last days. Apparently in modern panels the actual gate driver Transistors are integrated into the panel itself on the left and the right side. The external control turns on the gates line by line.

In case of a short on one side (e.g. left) that gate signal does not work correctly. However if you block the clocks on one side, the gate still opens on the other side (e.g. right). This might lead to timing violations visible in small bad lines, but at least the panel works again.

OK, that makes sense.
So perhaps the signal isolation does show up in special occasions and during a special type of picture or colour composition.

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

Just to double check: You did block two pins, CKV3_MB4 and CKVB3_MB4 and still had lines ?

I never tried that combination. I was thinking about it though if they both need to be blocked to get rid of the lines.
I will have a try.

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

CKV3_MB4 and CKVB3_MB4 isolated only does not give a picture. Only bootloop.

[Diah]

Re: Samsung 4K led model UE50NU7445U no picture

Yes, but the question remains - how can the picture work without the correct amount of clock signals ?

to get picture and no bootloop should at least one CKV line in place.. its + and -

the idea is if CKV signal occurs extremely the panel will be fault. and this is the case at yours TV. reduce the source will solve it.. as one chanel CKV remain in tact to deliver the frequancy to the liquid crystal cells.. this freq go thru all cells. each response on part of the freq. only in this way i can imagine it display complete screen by blocking some CKV signal

[Diah]

Re: Samsung 4K led model UE50NU7445U no picture

i think if this theory of extreme CKV signal was the result of boot loop .. if you as it working reduce the contrast and brightness below 50% then remove yours hide see if the it come on.. just theory

[Davi.p]

Re: Samsung 4K led model UE50NU7445U no picture

Answer to Powerampfreak, Gate drivers needs few signals, much fewer than source drivers, the fault happens when a mains surge will reach the screen, the spike goes through clock signals and destroy some circuitry on the panel side, if you block some of them you prevent the current to flow in wrong places and do probably an overload in vgh/vgl supply or protection of the tcon level shifter happens, without current the bad side will not work but the good one will do the job for the bad one too, if you see black lines spaced constantly, is maybe because the total overload will not reach the protection level, but some lines have still a short some where, for example in the remaining diode packs if there are..

[PowerAmpFreak]

Re: Samsung 4K led model UE50NU7445U no picture

That is interesting.
All in all, I won't mess with the set more now, afraid of destroying a connector or similair, have been trying quite a few combinations now.
I bought a new mainboard for it which was not necessary, I wonder if it's a good idea to use the new one or keep the old in place.
Both MB's works in the set.

I thank you all who contributed with advice. The result now is I got a 4k TV with no screen artifacts whatsoever after blocking 12 signals.
Obviously there are an internal panelfailure somewhere in the gate-driver circuitry, which means the panel is already broken so I won't care to find new ESD diodepacks to the bufferboards.

Found a good video about how the multiplexing in the panel works:
https://www.youtube.com/watch?v=izd7dhtmZjc