Support for UE50KU6070 [SOLVED]

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johnduff
Posts: 3
Joined: Mon Jan 20, 2025 10:09 pm

Support for UE50KU6070 [SOLVED]

Post by johnduff »

Hi !
After a few hours of searching the internets, I found this forum and kindly request a little help with this TV:
Model: UE50KU6070UXZF Version No 05
Main board: generic type JAZZ BN41-02528A / model BN94-11834W
PSU: BN44-00807A Rev 1.2
Symptoms:
-When I turn the TV on, the backlight flashes sometimes a little bit and then turns off. I can see the image with a lamp. After a little while, I can see the system restarting. When I press the power button, the led blinks fast but faintly until I release the button.
-When I disconnect the main board from the PSU, the backlight turns on and all the LEDs have the same brightness.
-When I disconnect from mainboard the left ribbon, right ribbon or both, the backlight still doesn't turn on.

A few people on facebook groups gave me contradictory answers, even sometimes quite illogical. Here are the ones that seem to make sense:
-Some of them said it was the PSU that couldn't handle both the mainboard and the backlight.
-Another guy said it could be the mainboard being dead.
-A third guy wrote that the display has a short circuit somewhere and would damage a new mainboard.

Now the questions:
-What fault sounds the most likely consistent with the symptoms ? PSU, mainboard or both ?
-Can you suggest test points to confirm either option? On the PSU I measured 12,83v on DM853C and DM854C after being asked to do so.
-I read about eeprom reset. Do you think it could solve the issue? I found the i2c connector. Is there something interesting to do with it ?
-I have found a guy that sells cheap boards for UE50KU6000 that had a broken display.
Main board: generic type JAZZ BN41-02528A / model BN94-10800D
PSU: BN84-10712A
Can I replace the faulty boards with the ones he sells ?

Thank you for your patience.
Last edited by johnduff on Tue Jan 28, 2025 7:13 pm, edited 1 time in total.
johnduff
Posts: 3
Joined: Mon Jan 20, 2025 10:09 pm

Re: Support for UE50KU6070

Post by johnduff »

I managed to start main board using my lab power supply (set to 12,83V). It works perfectly. I will swap the PSU board.
johnduff
Posts: 3
Joined: Mon Jan 20, 2025 10:09 pm

Re: Support for UE50KU6070

Post by johnduff »

Ok after swapping SMPS board the TV came back to life.
Faulty SMPS reacted the wrong way to 3.3V on POWER_ON pin: it turned backlight off instead of ON.
How to check:
1-disconnect SMPS from main board. Backlight turns ON -> backlight is OK
2-power main board with a separate lab power supply. TV works, and pin POWER_ON is 3.3V when board is ON and close to 0V when TV is switched off with the remote -> Main board is OK
3-power main board with SMPS but disconnecting POWER_ON pin. This is a cheap fix that prevents turning backlight off with remote controller but allows you to watch TV. You can just unplug the TV when you don't need it.
Fault: this SMPS board has an inverted logic, with 3.3V on POWER_ON it turns backlight OFF instead of ON

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