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

[triplefour]

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

No, i ment, you started the thread with no greetings, reading a big post is a bit challenging, a sign of thanksgiving or friendness does not hurt. A favor must be return back a day

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

[Davi.p]

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

No, i ment, you started the thread with no greetings, reading a big post is a bit challenging, a sign of thanksgiving or friendness does not hurt. A favor must be return back a day

[triplefour]

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

Greetings? I see no one..

I see dead tvs...

Here's a picture of what that pin 15 seems to do. I can't find out where it goes beyond this loop. It dispears via vias on both the mb and the panel boards

[Davi.p]

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

Greetings? I see no one..

[triplefour]

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

here is the ebay link to the replacement board that was purchased. i may have been hasty to order this one because he had another of the same boards listed but that listing actually shows a good picture displayed. this one shows a blank backlit screen like i get....but i only get that to be stable (no power cycle) if i block pin 15 or leave the second board disconnected!

https://www.ebay.com/itm/39418043975...rdt=true&rt=nc

ive asked the guy if he would let us do an exchange of parts... get the "known good picture" mainboard to work with instead of this possibly suspect one....

here is a link to the "good one"
https://www.ebay.com/itm/38503763832...&segname=11050

[triplefour]

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

Did you try to look into service manual? No more schematics, but at least there are connector pinouts
https://www.electronica-pt.com/esque...2-uwl01-85139/

wow thanks! ill have a look. i guess i shoudnt assume there is NO useful information in there...just not very much. not like...schematics or anything! but yes connector pinout is helpful!!!

--- oh dang i looked more closely and this is actually not for my model of TV. i have the 8000F and this pdf is for the 7000F series

i believe this is the correct manual:
https://www.electronica-pt.com/esque...ileinfo/83227/

wow...and i come to this line in the service manual:
"When replacing Main Board, certain values needs to be manually input in Factory menu to complete the replacement."

this cant possibly be true can it? ive never had to enter any factory menu to swap a board!


dang...and reading even further down it shows a picture of the mainboard and it is NOT the mainboard i have in this tv. it shows 2 connectors for left and right side of panel. i WISH my mb had that!

man... and almost 99% of the manual is just filled with useless garbage....endless lists of electrical parts with no way of identifying where on the board they are. does anyone find a use for this crap? or do they just make it to laugh at us?

the pinouts would be useful.... if they were for my board!

the manual references chassis UWK00
the only thing i can find saying chassis on the tv is a sticker saying Y20 TU7K ... but i am getting nowhere with that search.

[alfatv]

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

Did you try to look into service manual? No more schematics, but at least there are connector pinouts
https://www.electronica-pt.com/esque...2-uwl01-85139/

[triplefour]

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

i have noticed after much painstaking tracing last night that pin 15 goes to the first panel board, and to the second and somewhere on the second board, pin 40 connects to it (pin 15 and pin 40 appear almost as dead short on the second board only) and pin 40 goes back to the mainboard. so there is like a loop between 15 and 40 that i think makes sure all the panel boards are connected and throws an error if not? or does this loop actually go into the panel itself to check something? should i see resistance between these 2 pins on the second board or is a short normal? hard to know without looking at another tv, or a schematic!

[diif]

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

and what of my other questions? how does 0v on a power supply test point say anything about a panel? im quite sure that point in question is meant to be the ground of that particular test point?


...panel fault on a tv this new... bad samsung!

i am still hoping its something on the panel boards i can repair but ive checked all the mlccs i can see for shorts and dont find any...

If only there was a way we could visually confirm what is going on in that area.

It's poor consumer law/vendors you have over there. Some vendors sell their TVs with a 6 year warranty.

[triplefour]

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

so i must have been working too late and tired because i made a mistake and was looking at the panel connector backwards. i was blocking pins 15 and 16 but counting from the other side! so... not the clock 3 and clock 5.
i made a new piece of pin blocking plastic and made it extra thin this time to only block one pin. turns out blocking pin 15 makes the tv stable but still no picture and still no higher panel voltages.
here is which pin it is on the MB side.
i trace it to that solder point where it goes to a via and then poof! who knows where it goes!??

same happens on the panel side of the connector. i have to run for now but ill be back to try stabbing in the dark to see where this pin15 goes on both the mb side or the pb side.

[triplefour]

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

No idea why I wrote LG, replace LG for Samsung.

and what of my other questions? how does 0v on a power supply test point say anything about a panel? im quite sure that point in question is meant to be the ground of that particular test point?


...panel fault on a tv this new... bad samsung!

i am still hoping its something on the panel boards i can repair but ive checked all the mlccs i can see for shorts and dont find any...

[diif]

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

No idea why I wrote LG, replace LG for Samsung.

[triplefour]

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

The two voltages I asked for a diagnostic points. The 0V indicates a panel fault and that is the part LG would replace.
As the driver boards are attached to the panel they are classed as the same thing to LG. You can't replace one without the other.
If you can find a shorted capacitor on the driver board you are in luck, it's possible it's one buffer ICs, if not it's the panel.

this is a samsung tv not an LG and those two test points you asked for are on the power supply! how could that have anything to do with the panel?
one of them is 0v because its is ground. am i missing something here?

and the tv is out of warranty so SAMSUNG wont be replacing anything.

[diif]

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

The two voltages I asked for a diagnostic points. The 0V indicates a panel fault and that is the part LG would replace.
As the driver boards are attached to the panel they are classed as the same thing to LG. You can't replace one without the other.
If you can find a shorted capacitor on the driver board you are in luck, it's possible it's one buffer ICs, if not it's the panel.

[triplefour]

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

They are test points that indicate where the fault it. 0v tells us it's the panel.
The panel to LG is the replaceable part so it's on the driver board or panel.

sorry i dont understand. what exactly are you saying here? do we have enough information to tell which part has the problem?
are there more measurements i could take? i seem to have hit a wall with no way to tell for sure if the problem is from the mainboard, the panel board, or the panel itself.

what do you mean by "The panel to LG is the replaceable part?"

and what do you mean by "0v tells us its the panel" ? which 0v tells us this?

[diif]

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

They are test points that indicate where the fault it. 0v tells us it's the panel.
The panel to LG is the replaceable part so it's on the driver board or panel.

[triplefour]

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

I went back and put the tape on the panel cable to block those pins again and see what voltages look like then with a stable TV not turning on and off, both panel boards connected, still no picture. Turns out the pins I blocked are pin 15 and 16 from the left in my picture...which correspond to CLK3 and CLK5 ...the result is a stable TV with a blank black backlit screen but never any generation of the higher voltages (25v, 15v, 7v. 8v) that we see spike up and fall away when we leave those pins unblocked. How does blocking those two clock pins cause that voltage not to be generated?

[triplefour]

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

There were two test points next to the connector, you have given one, I don't think you have given the other.

I suspect the fault is in the panel or on one of the driver boards.

Yes as it behaves the same way even with the replacement main board we really have to lean toward panel or driver boards. There is always some chance that the main board they sent is defective in the same way. There were no pictures to prove otherwise.

I don't understand why you are concerned about the power supply though. It seems to check out 100%
Am I missing something here?

And those 2 test points near the psu to mb connector on the psu side? One of them is ground...so 0v

Obviously I am hoping the fault is in the main board or the panel driver boards and not in the panel itself, but more than that it is important for me to learn how to tell for sure which of the three it is!

[diif]

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

theres not much to tell about the power supply voltages. they are all there.
testing without plugged into mainboard:
there are only 13v power rails which are all there at 12.9v
there is analog dimmer (ANADIM) which when i measure it, the backlight dims a little and voltmeter reads 0.05v
there is power on/off which is at 4v
there is back light on/off (BLU_PWM) which is at 3.3v

There were two test points next to the connector, you have given one, I don't think you have given the other.

I suspect the fault is in the panel or on one of the driver boards.

[triplefour]

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

The ICs, what are they on the driver boards ? Not the Winbond.

i believe it says AAT7212
RJLFP0

and yes there are 2 of them. and they are same.