Samsung un65nu6900 bonds get extremely hot

[nomoresonys]

Re: Samsung un65nu6900 bonds get extremely hot

I should have said maybe try it with the one with a good picture but with a line, the one with no picture probably has a different issue. On the one with a display, did you clean the ribbon connectors and make sure they are seated properly and the lvds cable is clean and seated properly, also try a little heat with a hairdryer on the mainboard hit the capacitors eeprom/s and the processor, see if the line clears up if only for a while.

[budwich]

Re: Samsung un65nu6900 bonds get extremely hot

If I remove the left tab going from the Mainboard to the Panel, the right half of the screen comes up white, and if I remove the right side tab, the right side of the screen comes on white too. That is what's weird about these TV's.

Also, I did replace the mainboard on one TV, but with same result.

Will add a photo shortly.

Oh ya... I forgot that looking at the picture that you posted of the back, this set has no seperate tcon. The signal goes from the main to the panel drivers which may be a combined driver / tcon function. That will result in a slightly different approach. :-(

You are likely going to need to get at the bottom edge boards to look at there layout and labeling to see if there are some things to check.

since you have two sets of boards, did you try swapping the main from one to other... did the symptoms follow?

[itelite]

Re: Samsung un65nu6900 bonds get extremely hot

For what it is worth, there is a service bulletin from Samsung published in 2019 describing this problem and the solution is to replace the panel. It seems to be applicable to UN65NU6900 produced in 2018. Not that you will find it for sale anywhere but part number for the panel is BN95-05318A.

[henryvrensburg]

Re: Samsung un65nu6900 bonds get extremely hot

Hi guys,

I did replace the mainboard with a new board from SJ, but the result were the same.

The one that had picture, deteriorated while I was checking, cleaning the tabs etc. It now has exactly the same problems as the other. No picture, backlights, sound, no picture with flashlight, respond to remote. I can see no damage to anything, the tab bonds doesn't get hot, etc. I haven't taken of the side trim to get to the side bonds yet. I did inspect the bottom panel pcb, but no apparent problems, also nothing changes when I touch/apply pressure to tabs/bonds.

Nomoresonys, both TV's now have exactly the same issue. I'm sure the Power Supply is good, the Mainboard has been replaced(I tried the new one in both), now only the panel left.

[budwich]

Re: Samsung un65nu6900 bonds get extremely hot

so both sets are now showing nothing and when you remove either main to panel cable, the right side of the set goes white while the other half goes perfectly dark?

You need to look at the panel tabs on the bottom from the front of the panel... removing the plastic bezel to see things there. Look for "window washing" contamination at or near the bonded tabs. PS. the "tabs" that you referring to about cleaning are not really the "bonded tabs" that are connected directly to the panel from the driver boards at the bottom.

[henryvrensburg]

Re: Samsung un65nu6900 bonds get extremely hot

Yes, both sets are now showing nothing.

Thank you for the help. I will follow your advise, and report back here.

[Unspun01]

Re: Samsung un65nu6900 bonds get extremely hot

I had a chance to tinker with my UN65NU6900F. I am not original owner so I do not know anything about problem from previous owner.

When plugged in, TV backlights immediately come on, and dims or blinks on and off at seemingly random intervals. Turns off with remote.

When left or right side ribbon cable is disconnected from the panel, upon plug in, the backlights come on, and there is a startup sound from the speakers after about 10 seconds. The TV screen remains completely black except for backlight bleed.

I do not get "white" (or anything) on one half of screen regardless which ribbon cable is detached. Screen is completely unresponsive.

It is curious that I only get startup sound from speakers when left OR right ribbon cable is disconnected. Or BOTH ribbon cables disconnected. I can also hear audio cues when pressing up or down on remote control cursor.

When both ribbon cables are connected, there is no startup chime, and no sounds from speakers when pressing remote control buttons.

It's like the panel is preventing startup voltages or routine when both ribbon cables are attached.

[Unspun01]

Re: Samsung un65nu6900 bonds get extremely hot

I have an update.

I removed the two metal covers at the bottom of the panel to expose four narrow circuit boards which are directly connected to the panel with flexible COF (chip on flex) ribbon cables. I will call them 1, 2, 3, 4 left-to-right as viewed from back of TV.

Each of the four boards has 3 COF ribbon cables connected to the panel.

Circuit boards 1 and 2 are connected to each other with a removable jumper ribbon cable. 2 is connected to the left LVDS cable. 3 is connected to the right LVDS cable. 3 and 4 are connected to each other with another removable jumper ribbon cable.

With both LVDS cables connected to the panel circuit boards 2 and 3, I removed the left jumper between boards 1 and 2. When plugged in, the TV turns on with steady backlights and audio from the speakers.

Therefore, the issue is contained to the leftmost panel board #1.

In fact, using a DMM to measure across the small surface mount capacitors on the board, several of them measure as short circuit. Under magnifying lens, the 3rd COF ribbon from the left on board #1 has arcing damage where the IC is attached - The IC is shorted which damaged the flex cable. Neither is replaceable.

When the removable ribbon between boards 1-2 is re-connected, the 3rd COF ribbon cable on board #1 gets hot almost immediately and the TV backlights turn on and off repeatedly and no audio from speakers since the shorted IC brings the TV voltages down and TV detects fault.

Bad panel.

Interestingly: Several online parts retailers charge a "CORE" charge for the faulty panel when buying a new one so Samsung factory must be able to repair the panel by replacing this COF ribbon cable otherwise the "CORE" would have no value.

[Kilroy2k1]

Re: Samsung un65nu6900 bonds get extremely hot

the LVDS on the left side cover the first 4 pin with thin type then place it in. turn on.. hope it wil block the over clocking and remain on with out cooking

I also have one of these NU6900's where all the bond COF tabs along the bottom run very hot and the picture flips to vertical lines.

Could you describe which pins on which cable and which end of the ribbon you are referring to please?

Also I have markings of VGL1_-5V and VGL2_-10V on the mainboard but they actually Test out as -7V and -14.9V

Could these be part of what is overheating the COF tabs?
Thanks
Tom.

[itelite]

Re: Samsung un65nu6900 bonds get extremely hot

for what it's worth, i never went ahead with this test. It was a customer tv and i didnt want to give it back compromised in any way.

[Kilroy2k1]

Re: Samsung un65nu6900 bonds get extremely hot

I've seen the method used in many videos and it seems fairly safe as long as you dont physically short anything out to where it shouldnt be.
For me its a test to see if anything can be done to cool these tabs down.