1 Main Board vs Panel - Backlight Boot Loop
Model: UN65KU650DF
TV Symptoms:
Two thin vertical lines appeared in the middle of the screen a few weeks ago. I ignored as I was traveling. 10 days later and the screen is faded and bleached and the picture is totally washed out. TV still works.
Now the picture is completely gone and the TV is stuck in a boot loop. The backlight comes on, and immediately goes out within 2-3 seconds. No audio jingle, no dimming, nothing.
Here is what I have tried so far:
- Disconnect the main board from the power board and power on the TV. The backlight works fine -- > this probably means power board is fine. I even checked the out voltages out to the screen and they seem fine.
- When I reconnect the main board and remove either of the LVDS cables and then supply power the same symptom appears - backlight cycles ON and OFF in ~ 10 seconds interval. No boot audio jingle or picture.
- If I disconnect both LVDS cables from the main board..still the same issue.
- I ordered a replacement main board from eBay. I am sure its the correct model number for the main board (BN94-10828C). I replaced the main board with the one from eBay. Nothing changed i.e. regardless of whether the LVDS is connected or disconnect the backlight continues to cycle.
I'm running out of ideas on what to try and diagnose next. Could the cheapo eBay board also be faulty. I'm perplexed since I've seen in videos online that if the main board is fine then the TV at least boots up and then people try the tape masking process. In my case the TV does not boot up at all.
Link to Video showing the above symptoms
Main Board Images:
Main Board Full:
Bottom Right:
Bottom Left:
Top Right:
Top Left:
LVDS connection:
Power Board:
ScreenPCB Right LVDS:
ScreenPCB Left LVDS:
SMPS to Panel connector:
Ist dies eine gute Frage?
897 
2,4 Tsd. 
2 Kommentare
@emmbeeheavy "The backlight works fine -- > this probably means main board is fine" not really. all that means is that your SMPS (power supply) works. From what I read about you pulling the LVDS cables off, that is normal behavior. This is "Two thin vertical lines appeared in the middle of the screen" what is worrisome. WE really need to see all of your boards. Post some good pictures of those with your Question. Bilder zu einer vorhandenen Frage hinzufügen
von oldturkey03
@oldturkey03 Thank you for your response. Yes you are right. When the main board is disconnected and backlight comes on, I meant to say that the power board is fine. (Corrected this typo in the question).
I've added several high resolution images of the main board and SMPS board and screen PCBs and also added a link to a video that shows that symptoms I've described above.
I also suspect there is an issue with the screen due to the original 2 thin vertical lines that had appeared but its puzzling to me that when both LVDS cables are disconnected from the main board the backlight still doest stay ON. Does that mean the main board is telling the SMPS to power cycle the backlights ? Essentially, I do not know how to rule out main board vs screen issue and what to debug next.
von emmbeeheavy