SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

[Davi.p]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

First, i don't take care of Nomoresonys posts that i usually skip because scarce technically, i don't any further comment its totally unuseful comments...
The tv... sorry i can't follow you in all the posts long, understand me but my limitations in language etc etc.. i only suggest you to remove all the suppressor diodes in the bad board called T1-14, and remove all maskings, then try, for a safety reason put them in another place in order like were you took from.. bye..

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

I found that the points s12p, s12n were shorted to ground. I found that the short went away when I unplugged the board from the other one. I traced it to pin 42 on that connector which connects to pin 18 on the other connector which I had measured earlier as GND...which doesn't make a lot of sense...why should those points be grounded out? The black bar on the right side of the screen corresponds to s5p and s5n and those are also shorted to ground even when no other board is plugged in. So something is wrong in the COF5 area and I guess that traces to pin 18 which shouldn't be ground but is because of something in or around COF5, though none of the caps there are shorted to ground. I did the only thing I could think of and masked that pin 42, stopping it from connecting to pin18 and COF5 and stopping it from getting grounded out. The result is that the area in the previous picture that had the static has been replaced by a good picture. The static area has moved to being part of the 2 bar corruption at the far left of the screen. COF11 and COF12. Even though s12p and s12n are not shorted to ground anymore they still measure very low voltage like .05.
TESTOUT0-COF12 has 0.03v when most other COFS show 0.40 there. the other 2 points on COF12 are normal.
On COF11 the s11p and s11n have 0.42v like normal but TESTOUT0-COF11 is 0.03v just like on COF12.

I think it was COF10 that originally had the static but now it seem fine.

COF5 testout0 is only 0.30 when others are closer to 0.40. Other 2 points look fine but s5p and s5n are at 0.02v. That area of the screen can look like static or black depending on flexing that area of the board. Or at least it was like that before I masked pin 42. Now it just stays static. Strange behaviors! But I was able to get one more COF of picture!

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

My pin mask was off by 2 pins somehow! It was blocking rhe 7v. With that taken care of i get this "clear" picture but still with the bad sections.

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

i spent a few hours yesterday not trying to fix the tv but instead, refining my environment, my techniques, and tools. i measured and cut up a bunch of "pin mask" strips of varying widths from 1 pin up to 14. tape by itself just doesnt work well for me, so i prefer to use some very thin but still stiff plastic combined with some tape to hold it in place. having those done and at the ready will save me a lot of fiddling around cutting these things in the future.
I took a few steps to create a more comfortable setup to work on tvs and take measurements, and the result is quite nice. I was able to measure and record the 60 pins going to that second board without the insanity inducing frustrations I was having earlier. I raised my workspace so that the TV is at a good chest height now so I'm not leaning over like I was. I got a good strong light and a magnifying glass involved. i got a very fine tipped felt pen. a micron 005 with which i can actually mark individual pins pretty easily. i put marks on the connector at 5 pin intervals and that helps A LOT. also i found a sewing pin with a finer point than my probe and wrapped it to my probe tip with a piece of silver wire. through the magnifying glass i realized where the safe place was to slip the tip of the pin into to read one and only one of the pins at a time. i had been trying to get at the pins from the back of the connector where they are soldered to the board, but i realized that from the top of the latch you can measure them more accurately. all of these things i did are quite simple, but combined they make the process bearable. the last thing i did to make it easier on myself is that instead of taking a break to write down each value, i found it much faster to use the voice recorder on my phone to record myself calling out the pin numbers and the values, and then just listened to it back and wrote them all down. WAAAAY faster than the alternative.

using my new pin masks, i seem to be getting more consistent results. now masking those 14 pins does get most of the screen going. the color is washed out and there is still that one black vertical bar on the right hand side of the screen, and there are 2 bars of the left side of the screen that are wrong too. one is some kind of static, the other is just black and twice as wide as the one on the right. on the COF test points related to those areas that have the black bars i am getting hardly any if any voltage compared with the normally functioning ones which i have listed earlier as 1.85v,0.1v,0.38v
i noticed also that the IC that is on the left panel board has the same 15.6 voltage on pin 8 as it does on the right side but all the other voltages are much lower than i would expect. pin 5 on the right reads at 7v but on the left board its 0. the other pins are all less than a volt.
ill see if i can get a datasheet on that IC. and try to trace where i that 7v should come from.
while i was probing that IC a couple of times my probe slipped and i might have jumped 2 pins but the picture became clear. still missing those bars but the washed out went away. it came back eventually though. but i saw that also when i was trying all kinds of pin masking the first time. theres got to be some way to at least get it to stay there! and then figure out how to turn on those cofs that are staying off? probably impossible. could be internal panel damage. but i went to look at another TV the other day and its almost this same model but a 58 inch and it has almost the same kind of problem! reboots when the second panel board is plugged in but otherwise stays on. these tvs are just barely a year old. have they gone full evil and are making panels with timed explosives in them????
no reason to give up while im still learning!

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

The guy decided to give up on fixing it and didn't even feel like returning the main board. So he gave it all to me. Basically I'm free now to try any crazy thing I can think of or be suggested to do to this panel to try get some results or at least some education from. Any ideas?

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

With this mod you get stable image, but very tinted on left side. The reason is missing VGH.
May be still the best option if nothing else can be done.

i did this. tv stays stable but then i dont get any image on either side.
something is making all the COF TEST OUT pins read 0.

[alfatv]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

Usually these 14 pins need to be masked.

With this mod you get stable image, but very tinted on left side. The reason is missing VGH.
May be still the best option if nothing else can be done.

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

Usually these 14 pins need to be masked.

I did this and for a little while I did get some picture on the left side. 2 of the areas were corrupted tho. Same width as the black bar I described earlier on the right side. Of the 2 bad areas 1 was all kinds of moving static, and the other was just black. Other parts looked good. While I was trying to get a reading on the COF TEST OUT pins, the picture went away and so too the voltage on those COF OUT TEST pins. I tried all kinds of tape masking but could not get that left side of the panel to do anything anymore. None of the COF turn on. All other voltage is there. The area of the screen on the right side with the bar has the same problem too. That COF is not getting turned on? I don't really care at this point if I fix the TV though I really would like to. I just want to understand panel and tcon logic!

Masking those 14 pins are the clock signals for that side of the panel. I found I only have to mask a few to get stable voltages but the right side panel won't display any image unless I also mask some other pins on the cable. By my count it's pins 43, 42, maybe 41... I need smaller eyes!

[lotas]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

Usually these 14 pins need to be masked.

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

I just don't know when to give up! I decided to keep going with masking pins, and on the first try, this big piece of tape masking a whole lot of what I assume are signal data pairs, while leaving the high voltage and the necessary pin 45 and pin 1 unmasked to complete the connection check loop...has resulted in a stable tv, all 16v, 8v, 7v voltages present and the picture no longer looks washed out. Still only seeing image on the right side and still having that black bar. But I think this proves I dont have any hot short on any of the higher voltage rails on the left board....so something wrong with one or some of the pins that tape is blocking. I can't stop now! Gotta keep cutting tiny pieces of tape lIke a madman late into the night!

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

You were not being rude, I myself like to get right to it, and appreciate not having to read extra words that don't pertain to the problem at hand, if someone wants to be greeted by hello I'm blah blah from blah blah, maybe they should try social media. THIS is a tv repair board. I can only put up with x number of those BS remarks before I have to respond.

Thanks for the support, mate
So I've made a little progress. I was looking at that tracing I did and guessed correctly that this loop just tells the mb that the panel boards are connected. If I short pins 1 and 45 on the connector that goes to the second board that I leave disconnected, I can "trick" the TV into thinking that the second board IS connected, thereby allowing the TV to stay on stably, and produce the 15v and 8v and 7v for the panel boards, which the right board (first board) makes use of to display...almost...half a picture. There is a concerning black vertical bar about an 8th of the screen wide right in the middle of the otherwise visible right half of the screen. The color looks washed out in the picture. I was still using the clients old mainboard. I switched to the new one and got a better picture but still that black bar.
So both mains appear to be functioning OK, and it really looks narrowed down now to something on that left panel board which shows no "cold shorts" on any of the caps. I tried masking the pins responsible for the 15v coming into the second board and also the pins next to them for the 8v but I couldn't get the TV to be stable. It still kept getting up to about 7v on that big cap and then falling over and over. Masking these tiny pins is so tedious...
so the only thing I have left at this point is voltage injection....unless there are any objections or interruptions I'll probably be doing that tomorrow. Injecting 15v into the big cap nearest the connector on the left panel board. What current should I start at and what should I expect to get up to before it's dangerous? Seems it could damage the panel itself if too much current?

[nomoresonys]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

i was not aware i was being rude in the way i started my thread...

rest assured i have the warmest feelings in my heart for anyone on this forum, especially those who take the time to post. we are all in this together are we not? and i feel i have shown my appreciation numerous times by being an active member of the forum, trying to help on other posts where i have something to add, and of course thanking anyone along to way who tries to help!

GREETINGS, EARTHLINGS!!!
ALOHA FROM HILO, HAWAII

You were not being rude, I myself like to get right to it, and appreciate not having to read extra words that don't pertain to the problem at hand, if someone wants to be greeted by hello I'm blah blah from blah blah, maybe they should try social media. THIS is a tv repair board. I can only put up with x number of those BS remarks before I have to respond.

[Davi.p]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

hi, there's no need now to inject on cpu or similar, instead in other situations yes, sometimes cpus fries..

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

sorry, in italian the more used one is "condensatore" , much more than "capacitore" , yes it is the same, i will try to remember to use only "capacitor"..

No need for apologies my friend! Thank you for helping me understand these circuits and working through a language barrier no less! Much respect!
I have dusted off my barely used bench power supply and found that it seems to work pretty well. It gives correct results with my tests using a 25 ohm resistor and ohms law. The only thing I am not sure of is that it can only go down to 2.5v max voltage even though I turn the knob all the way counter clockwise. And when I short out the leads and try to set max current I can only go down to 0.19A. When I put 25 ohm resistor and 2.5v I get 0.1a which is about right. And when I adust the voltage up I can get it to 0.19A at 4.5v which is about right. Resistor gets pretty hot then so I don't do that for long of course!
If I adjust the current knob then I can make it go even higher, and the voltage increases too and the resistor gets even hotter.


So I think I'm ready to try voltage injection for this case...but I think I should practice on some dead mother board or graphics card first maybe...and what if I need to inject less that 2.5v ? Don't cpu and gpu run off of 1v?

[Davi.p]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

sorry, in italian the more used one is "condensatore" , much more than "capacitore" , yes it is the same, i will try to remember to use only "capacitor"..

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

sorry my errors :

..biggest condensers..
therefore.. forget about testpoints, easier way, on a biggest size condenser apply the voltage as i have explained, increase current slowly, keep fingers on condensers..

Is condenser another word for capacitor ?

[Davi.p]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

sorry my errors :

so mandatory, on panel's boards the bigger condensers

..biggest condensers..
therefore.. forget about testpoints, easier way, on a biggest size condenser apply the voltage as i have explained, increase current slowly, keep fingers on condensers..

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

Ok, you can be the most correct man in the world but not everybody nows you, a little advice, never forget at least a tiny "Hi, " in the beginning. Now the tv, sorry read very fast all long thread because reading the first post it's almost clear to me it's the frequent common problem of the panel's boards, almost surely a bad condenser, the odd thing is you don't see a cold short, but we can make it explicit, much probably it's the AVDD/source tension rail that is at fault, so try to locate a test point for that rail, not so mandatory, on panel's boards the bigger condensers paralleled thogether are for that rail so, connect to one of them a bench psu at 15v starting low current, increasing one of the caps would go short and you will feel heat on it.. ah, for last the short is in the second board, so you can test it also alone with nothing connected..

thank you. it sounds like you have more experience than me with this stuff. I will love to perform any other test i can manage on this TV just to learn more. I do have a bench PSU which i hope actually still works as its been sitting for a long time almost never being used... but this test point AVDD/source tension rail you speak of... i dont see any markings on the board for that. one of my posts here lists all the test points and their labels i was able to find and measure. is it one of those but the name is different?

[Davi.p]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

Ok, you can be the most correct man in the world but not everybody nows you, a little advice, never forget at least a tiny "Hi, " in the beginning. Now the tv, sorry read very fast all long thread because reading the first post it's almost clear to me it's the frequent common problem of the panel's boards, almost surely a bad condenser, the odd thing is you don't see a cold short, but we can make it explicit, much probably it's the AVDD/source tension rail that is at fault, so try to locate a test point for that rail, not so mandatory, on panel's boards the bigger condensers paralleled thogether are for that rail so, connect to one of them a bench psu at 15v starting low current, increasing one of the caps would go short and you will feel heat on it.. ah, for last the short is in the second board, so you can test it also alone with nothing connected..

[triplefour]

Re: SAMSUNG UN50TU8000F rebooting, backlight ok. No 12v to panel boards.

after thinking about it for a while, i really cant say i know anything about that circuit ive been tracing that goes out on pin15 and comes back in on the last pin (i labeled it 80 but it was just a guess)

for one thing, i dont know that it "goes out" on 15 and "comes back" on pin 80. i dont know the way to tell if it isnt the other way around in fact.
also i dont know if this circuit is merely a single uninhibited wire that when connected, simply tells some part of the mainboard that both panel boards are connected.
essentially i dont know whether i should expect to see some kind of resistance on that line, or not, under normal conditions.

all i do know is that blocking this line, stops all the other high voltages being created. and thus stops the power cycling. basically giving the same result as if the second panel board were not connected. which maybe means theres nothing wrong with this line, its just doing its job.

i do see a voltage of 3.22 volts on this line (on both pin 15 and "80") that is there and then drops out when the tv power cycles. ive tried to find on the mainboard where this 3.22v comes from but i cant see it anywhere else on the board
really getting hamstringed here in my quest for knowledge by a lack of a schematic or pinout diagram. i feel the only way is to possibly look at schematics and pinouts of "similar" samsung tv's and try to make some educated guesses... definitely over my head at this point, but if you're trying to learn something, you should be excited by what you dont know yet, and i am! just want to know more!

a pinout of these connectors might be helpful if i could decipher the pin names to something meaningful. I would love to test and trace each one of these pins but with so many there in such a tight spot, i dont see how to do that without driving myself insane.