Samsung QE65Q700TATXXC is not starting

[K212]

Hi,

my Samsung QE65Q700TATXXC has stopped working recently. It worked fine during the morning, and when trying to start it later the same day it just refused to start.

The standby LED is working, but nothing happens when pushing the power button, other then the LED blinking once. No picture, no sound, no chime, no relay click. I tried a cold start, and other recommended fixes from Samsung. Nothing worked. Then i even tried to reflash the firmware, but nothing happened, not even flashing of the standby led etc.

I contacted Samsung support who said it is most likely the main board or the PSU, and that neither are being fabricated anymore and buying them 2nd hand would be very expensive.

I managed to open the backside of the tv and tried some more things with the help of chat gpt.

When the cable between the mainboard and the psu is disconnected, the backlight turns on and stays on. LED strips seem to work. So most likely the PSU is fine.

Bridged PS_ON to gnd, no backlight, only disconnecting the main board triggers the backlight.

I managed to remove the mainboard, visual inspection did not reveal anything weird yet. Didnt manage to remove the heat shield which covers the majority of the board (yet) though.

Main suspect: Possibly bricked mainboard or failed SPI flash / EEPROM (firmware corruption), since the PSU and backlight behave normally once disconnected from mainboard. PSU likely good. T-Con not tested independently yet.

I cant seem to find any manuals with details on the boards themselves, which would be very helpful...

I need help with finding the SPI flash chip or EEPROM on BN94-15931L / BN41-02958B board, so that I can try resetting it in case it is bricked.
or any other ideas...

thanks

[mrtek]

What happens if you disconnect the cable from the main board to the buffer boards / panel?
Some pictures would be nice.

[K212]

Here are some pictures. I will do that test later today if I can.

[K212]

Alright, so now I’ve tested a few more things. Here are the results:

1. Everything connected:
When powered, there’s a slight buzz from the T-Con and a very gentle, quiet whine (or high-pitched beep) from the main board.


2. Main board disconnected from T-Con:
No backlight, screen remains completely black/unresponsive. Same sounds as above (T-Con buzz + main board whine).


3. Main board and T-Con reconnected. Disconnected the left 2 ribbon cables from the T-Con (going to what I believe are the buffer boards for the left side of the panel). Right-side ribbons stayed connected.
Result: No backlight or audio. T-Con was silent. Main board still made the quiet whine.


4. Reversed the test (disconnected right-side ribbons instead, left-side connected):
Same results as above — no image, no backlight, T-Con silent, and main board continued with quiet whine

[EazyBone]

This has probably been answered.. I need to find the thread. The main board goes bad. Reflowing the CPU on the top left is the fix for it. I'll try and find thread.

[Davi.p]

I have lost a file with some samsung led error codes, i remember some around bad cpu/software for the 1 blink, there's a problem maybe on one of the bga ic on main board, i barely remember a similar case on a similar chassis, the culprit was a ram ic, first thing to do is for me do a light heating with no flux on those ic , then get the board as cold as possible (even on a fridge for some minutes) then try turn on, a small improvement indicate that the way is right, but if so it is not easy to proceed as the entire set of bga reballed by a lab can be very expensive..

tried some more things with the help of chat gpt.

good this.. this is the new era of donkey men, for your info those chat feeds themselves with public internet info, the more the people rely on these tools the less good info there are around, IA is not a tech, is only voyeur of internet, they list you all of the less technical info around , and is a big loss of time most of the times..my opinion..

[K212]

I could probably inspect further if I can remove those heat shields, but I am uncertain how to do that without possibly damaging the board. Any help there would be appreciated as well.

[Davi.p]

if you have an heat gun or hot air station you can warm it for 1 minute at 200 celsius and the rest said..

[Diah]

Bridged PS_ON to gnd, no backlight, only disconnecting the main board triggers the backlight.

wow... where did you read this test !!, you killed yours MB,

[K212]

Chatgpt.. it was already dead tho?

[K212]

if you have an heat gun or hot air station you can warm it for 1 minute at 200 celsius and the rest said..

Can you elaborate some more on where exactly to apply heat? The heat shields seem to be held in place with some kind of anchors (plastic or metal), that have some kind of spring under the caps?

Also, I only have a simple soldering iron that I can't change the temperature on...

[nomoresonys]

That tv is a bad bet, you need to also look at refresh rate, which is only 60 Hz. Why would anyone do that to an 8k tv. More samsung shenanigans, I'll say it once more, SHAME on samsung. A problem with it is it will not even support 4k 120 Hz content.

[K212]

I should probably also add that Samsung support suggested to buy a new one. The support guy said that it most likely was the mainboard or PSU. None of these are fabricated anymore and 2nd hand ones cost about half as much as the tv itself.
I'm just trying to give it one last shot to try to fix it myself..

[nomoresonys]

With samsungs recent reputation, the last thing you want to do is buy an 8k tv from them. Myself I wouldn't buy an 8k tv at all. By the time there's enough 8k content available to make it worth while, most tvs bought today will be dead way before then. My purchase would be 4k 120 Hz.

[nomoresonys]

MOST all the time the test you did in post # 1, verifies backlights and powerboard are good. That leaves the rest, everything after the powerboard that could be the issue, likely the mainboard.

[nomoresonys]

Not familiar with this mainboard, maybe look at the bottom side. See if there's little plastic bits poking thru that need to be squeezed together and poked thru to release the heatsink.

[K212]

Not familiar with this mainboard, maybe look at the bottom side. See if there's little plastic bits poking thru that need to be squeezed together and poked thru to release the heatsink.

Yeah, where those circular markings are (see picture), a tiny bit sticks out from those anchors. So I just squeeze them and pull gently from the other side then? Do I need to be careful with those springs?


also note, I have an arduino board that perhaps could be used to read some data of one of the chips??

[nomoresonys]

If it's the type I'm thinking of you need to remove the mainboard from the tv, turn it over, spot the plastic bits sticking thru, use tweezers or such to squeeze them to release, use magnifier if needed.

[nomoresonys]

Once those are released then gently twist side to side to loosen the heatsink compound, it may pop right off with no trouble.

[nomoresonys]

You can try a test once you get the heatsink off, heat the chip with a hairdryer for a minute or two, then try the tv, see if you get a display but don't run it for too long this way because the heatsink is off.