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Crumbtrail TV Forums: TV Equipment: TV Repair Forum:
Samsung UE55JU6875 - 1/2 Backlight Failed, Power Sup. or LEDīs?

 
 


Tomas02
New User

Mar 22, 2019, 7:39 PM

Post #1 of 4 (1101 views)
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Samsung UE55JU6875 - 1/2 Backlight Failed, Power Sup. or LEDīs? Can't Post
Hello everyone

I have a Samsung TV over here that only lights up 4 of 9 backlight strips/rows.
I think the power supply feeds the lights with two ~100v leads but when measuring with the TV on and the lights connected they read:

1: 1
2: 105v
3: 195v
4: 5v

What I am wondering is this normal when LED lights starts to go out, that the voltage shots up high in that specific pack?
Is it normal for the whole side (5 rows in my case) to die when one or two lights go out, and do all the strips/row get damage with the higher voltage? In other words: is it worth checking the 5 dark rows to see if any of them are fine?

Or is this simply a power supply issue?
Power Supply: UN55JS700DF BN44-00859A L55SHN_FHS
Best regards,
Tomas



jts1957
Veteran


Mar 23, 2019, 9:42 AM

Post #2 of 4 (1088 views)
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Re: [Tomas02] Samsung UE55JU6875 - 1/2 Backlight Failed, Power Sup. or LEDīs? [In reply to] Can't Post
Just replace bad LEDs and reduce backlight intensity.


Sammy decided that backlights at full intensity helped sell TVs, while ignoring even their own designer's warnings that doing so would seriously shorten the life of the LEDs.

LEDs wired in series. Take number of LEDs in a string and multiply by the individual LED voltage of 2.5 to 3.5 volts to obtain approximate total voltage.


-------------------------
Location: Far, Far Away


Tomas02
New User

Mar 23, 2019, 10:02 AM

Post #3 of 4 (1085 views)
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Re: [jts1957] Samsung UE55JU6875 - 1/2 Backlight Failed, Power Sup. or LEDīs? [In reply to] Can't Post
Thank you for answer, I will open the TV and replace the 5 rows.
Also I will reduce the backlight when itĄĶs working again.

And a small correction, it seems that Pin 1 on the connector is at 320v, my first meter did not measure over 200v in DC. I assume the LEDs are powered with 3 leads with 3 rows each, which make much more sense.

I was just hoping that the power supply was the culprit as it is a bit easier to replaceĄK Thanks again
Best regards,
Tomas


Tomas02
New User

Mar 24, 2019, 12:20 PM

Post #4 of 4 (1073 views)
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Re: [Tomas02] Samsung UE55JU6875 - 1/2 Backlight Failed, Power Sup. or LEDīs? [In reply to] Can't Post
So, when I first got this TV there were no backlight at all, disconnected main board and T-con and tried it again, it lighted up (don't know how many rows though) and after connecting main and t-con again the TV worked but with only half of the backlights.

Dismantled the TV and removed the 5 failed rows of backlight, I then switched placed on the working ones and placed the bad ones where the good ones where, just to make sure that they don't work.
To my surprise they now all worked, every LED, it must have been a bad connection...

But in the dismantled process the small plastic blue holders for the speakers got destroyed and I cant seem to find them on the net, I have been at it for literally hours...

Is there anyone out there that know where I can find them?
Regards,
Tomas

 
 
 


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