Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

[dchang0]

Hi, everyone--

I've got a Samsung UN55KU630DFXZA or UN55KU630DF, Version CA02, that does this:

1) Plug in power cord.
2) Backlight comes on and SMART TV logo is visible. This logo screen looks perfect. No sound (not sure if there is a startup sound or not).
3) Logo screen quickly turns off, backlight turns off.
4) After a few seconds, backlight comes on regardless of whether power button was pressed. Screen is black with backlight glow. No menu, no sound, none of the inputs work. I can press the joystick button in the back and the IR light flashes, but nothing happens (no sounds that would indicate moving around menus, etc.) TV will not turn off no matter what I do except pulling the AC cord out from the back.

A visual inspection of all the boards including the display drivers at the bottom edge of the screen didn't show any obvious burn or water damage marks.
Plugging a laptop in to the HDMI 1 input does nothing on the TV, but the laptop is aware that the TV is attached and is aware of the 4K resolution.

The power board is Samsung p/n BN94-10712A. A huge close-up photo is on ShopJimmy's site.
The mainboard is Samsung BN94-10838R. A huge close-up photo of that is also on ShopJimmy's site.
There does not appear to be a T-CON board.


I checked the voltages on the cable between the mainboard and the power board on the power board side while all boards were attached and the voltages all are within the spec silkscreened on the power board (They say 13V but another label clarifies that 13V is supposed to be 12.8V, which is exactly what I got).

EXCEPT: one test point J823 was a bit high. That pin's silkscreen said that while the TV is on, it should be 11.8V and while on standby, 7.5V. The actual measurement was 12.8V, which was the same as the output-to-mainboard pins, but I am not sure whether the TV is on or on standby while in this frozen state. Is 12.8V too high for 11.8V? Probably.

This feels like a mainboard issue and the power board is actually okay, but I don't want to buy a mainboard, drop it in, and have the power board kill it.

I found the EEPROM (label is IC1104) and tried shorting pins 5 and 6 on power on but nothing changed.

So, I'll go back and measure the power board and post up the values here, now that I have a better idea of how to measure the COLD and HOT sides.

Any tips or questions or a service manual/schematic are much appreciated.

[Davi.p]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

Hi, your problem is only software, I had an Hisense smart TV with the same exact behaviour, i had to buy a replacement board, but after this i have inspected the original board, done a lot of research and i think i was near the solution for it, So start to search for a new board. Bye.

[dchang0]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

Hi, your problem is only software, I had an Hisense smart TV with the same exact behaviour, i had to buy a replacement board, but after this i have inspected the original board, done a lot of research and i think i was near the solution for it, So start to search for a new board. Bye.

Thanks for your advice!

[Davi.p]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

i have forgot to mention MAIN board... and the fact that is enough to change the flash mem chip with a one programmed, but if is nand flash is more easy, if is emmc is less easy or difficult.

[dchang0]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

i have forgot to mention MAIN board...

Oh, thanks--that's what I thought you meant.

Do you think that replacing just the EEPROM will work? (ShopJimmy does not have the main board in stock.) I expect that replacing the EEPROM will not fix the problem, but if it could, it would cost much less than the whole board.

Thanks again!

[Davi.p]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

eeprom is a generic term, if you mean the small i2c 8 pins one it does not contain software. If you don't find a repl. board i can offer a fixing job, i don't desolder any component, i work only trough the uart serial port if exists, but the shipping and other fees will cost too much i think, and after i saw from a picture of board that there are no video output connections to test the board so this way is impossible.

[dchang0]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

Thanks for offering. You're correct, the shipping and other fees would be too high relative to the cost of a replacement board.

Thanks for clarifying that the EEPROM does not contain software.
I'll order a main board ASAP.

Also, Happy New Year!

[dchang0]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

Davi.p:

Thanks very much for your help. Replacing just the main board did indeed fix the TV. It booted up right away (much faster than my broken board did).

Hopefully this thread helps a person with the same TV and same problem in the future.

Thanks again!

[comptek]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

Had a UE55KU6100KXXU had the similarities to yours
And yes replaced the mainboard and it's also sorted now

[dchang0]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

Had a UE55KU6100KXXU had the similarities to yours
And yes replaced the mainboard and it’s also sorted now

Thanks! Do you recall how it got that way? I'm wondering if this is the result of firmware bricking or something along those lines. (I got this TV from a neighbor who was throwing it out; they could not tell me how it went bad.)

If the user can cause this problem, then it would be nice to know what to avoid.

I'd really like to figure out how Davi.p fixed the bad board with the UART. I have a USB-to-UART dongle from programming Arduinos, just no know-how on programming Samsung TVs.

[mdneilson]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

FYI. I had this happen to a set. All that I did was factory reset!

[dchang0]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

FYI. I had this happen to a set. All that I did was factory reset!

Nice! I should try that (I still have the bad board).
How did you do the factory reset, if you don't mind sharing?

Or, if you could post a link to some documentation you followed...

Thanks!

[Davi.p]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

I don't think the user have resolved, for me mine was a mistake, i did solved an Hisense issue not Samsung, Samsung instead have massive protection on the system access, no luck for now, on a Samsung smart tv by year 2012 i have unlocked the boot process by modifying the settings eprom, only a single byte, then the tv showed a new defect, channels memory lose.. this is not solved until now, i'm still with theese works since a lot, i'm changing home and i don't know where to store all my tvs..
the real important thing in this post is that theese faults comes out from making updates, Samsung puts malware that locks some functions so it can earn from assistance or new set buying.. sounds paranoic but it is documented by users complaints in the samsung site's forum..

[dchang0]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

I don't think the user have resolved, for me mine was a mistake, i did solved an Hisense issue not Samsung, Samsung instead have massive protection on the system access, no luck for now, on a Samsung smart tv by year 2012 i have unlocked the boot process by modifying the settings eprom, only a single byte, then the tv showed a new defect, channels memory lose.. this is not solved until now, i'm still with theese works since a lot, i'm changing home and i don't know where to store all my tvs..
the real important thing in this post is that theese faults comes out from making updates, Samsung puts malware that locks some functions so it can earn from assistance or new set buying..

Very interesting! I wish I could do what you're doing (hacking the EEPROM). Thanks for the explanations so far!

[mdneilson]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

Nice! I should try that (I still have the bad board).
How did you do the factory reset, if you don't mind sharing?

Or, if you could post a link to some documentation you followed...

Thanks!

Sorry that I was unclear. Factory resetting broke the TV. Clearing the EEPROM has brought it back a bit, but going through the setup has broken it again.

I live close to shop Jimmy, do I want to pick up a new EEPROM, but I'm not sure if the CA02 chip will work with the CJ05 board.

[dchang0]

Re: Samsung UN55KU630DFXZA: Smart TV logo comes on, backlight off, then on, but blank

Sorry that I was unclear. Factory resetting broke the TV. Clearing the EEPROM has brought it back a bit, but going through the setup has broken it again.

I live close to shop Jimmy, do I want to pick up a new EEPROM, but I'm not sure if the CA02 chip will work with the CJ05 board.

Ohhhhh, my bad. I misunderstood you.

Sorry to hear that it happened to you and that it's not fixed yet.

I tried resetting the EEPROM but it did nothing for me. Based on that and the explanations from Davi.p, I decided not to try to replace the EEPROM and instead replaced the whole board. However, if it does turn out that replacing just the EEPROM definitely fixes the board, I have the bad board and am able to desolder and solder SMT, so I would indeed go ahead and replace the EEPROM to have a backup board on hand.