Question Samsung UE55JU6500 TV screen has gone black ?

[snodge182]

Hi!

We have a Samsung UE55JU6500 65" 4k (non HDR) TV and it's recently stopped displaying anything.

I'd like to preface this with for a while it's been having a little issue whereby while watching any input source, the screen goes black for a couple seconds and then comes back on. Not a power cycle as the standby light doesn't change and the TV doesn't come back with the boot up icons or anything like that.

Today however, while watching netflix the TV has done it again, though this time it hasn't come back on since.

We have a Samsung soundbar connected to the TV wirelessly and sound is still coming through the TV, but no picture - no backlight even! We can still control the TV with the remote, volume/power etc and the standby light indicates it turns on when we tell it to and turns off when we tell it to.

To try and resolve this, I have tried power cycling the TV by unplugging power, holding the TV power button for 15 seconds and then leave alone for at least 30 seconds before plugging back in and it didn't help.

I'm not averse to opening her up and switching out a board or two, but I don't know what board would be the culprit in this case.

Can anyone give me some pointers or idea of what's gone wrong?

Any help is much appreciated!

 

[Eximo]

Given that audio and other stuff is working, the AC to low voltage board is still working, which is usually what gives out first on TVs. So the board where the cord plugs in is likely fine.

Sounds like the backlight board/circuit has died. Open it up and look for bulging/deformed capacitors. Usually the first thing to go in a TV. You can often find capacitor replacement kits for models of this age. (You still need to know how to solder and have the equipment)

Getting the whole board might be a possibility, shop around on Ebay. Parts often come from TVs that have had their screens physically broken.

To confirm take the back of the TV off, see if shining a bright light from behind reveals the picture. If not, then the LCD controller might be the culprit. Typically this would be the same board as the backlight, so replacing that whole thing may solve the problem relatively cheaply.

Given the age of the TV though, something else could also fail relatively soon. You have to balance repair costs with the cost of a replacement 65" TV.

$450 - 550 for a 65" 4K Smart Samsung...
$750 for their pretty good QLED TVs.
And $1000+ for an OLED

 

[snodge182]

Given that audio and other stuff is working, the AC to low voltage board is still working, which is usually what gives out first on TVs. So the board where the cord plugs in is likely fine.

Sounds like the backlight board/circuit has died. Open it up and look for bulging/deformed capacitors. Usually the first thing to go in a TV. You can often find capacitor replacement kits for models of this age. (You still need to know how to solder and have the equipment)

Getting the whole board might be a possibility, shop around on Ebay. Parts often come from TVs that have had their screens physically broken.

To confirm take the back of the TV off, see if shining a bright light from behind reveals the picture. If not, then the LCD controller might be the culprit. Typically this would be the same board as the backlight, so replacing that whole thing may solve the problem relatively cheaply.

Given the age of the TV though, something else could also fail relatively soon. You have to balance repair costs with the cost of a replacement 65" TV.

$450 - 550 for a 65" 4K Smart Samsung...
$750 for their pretty good QLED TVs.
And $1000+ for an OLED

Thank you for getting back to me Eximo.

I tried looking for bulging or deformed capacitors and they all look good. I stripped the TV back to the backlights but didn't want to take the last sheet out because it's very delicate, so I wasn't able to see the backlight board.

I had a look at the TCONs board and that looked fine (no blown electronics).

I saw a post on youtube of someone with the same TV, the backlights weren't turning on so he unplugged the main board from the power board and they came on. I tried the same with mine and the LEDs also turned on. I'm not sure what that means, but I then tried doing what he did to fix his TV which was to replace the main board. That hasn't worked, I'm still having the same issue.

I am considering selling the TV spares or repair and putting towards a pot for a new TV, but the price tags are heavy. Plus, we have the HW-J6500R soundbar, which is supposed to be the ideal counterpart to this particular TV.

One last check might be the TCONs board, though I'm not sure if that'll help in this case. The fact that the LEDs come on without the main board attached could mean it's a power board issue perhaps, though I'm not sure. I couldn't find an adequate place to shine the torch through to light up the LCD but perhaps the LCD is or isn't fine - would that be a separate issue to the backlights not coming on, considering they are separate boards?

 

[Eximo]

Well that says the LEDs themselves work as well as the power to them.

By disconnecting the main board I assume you mean the brains of the operation. If the LCDs default to wide open do you see a full white image on the other side? That says the LCD controller has failed, and if replacing the main board did not fix it then the failure could very well be within the LCD panel. Replacement panel would only really come from a TV with a power/logic problem and that might have other problems.

 

[snodge182]

The video I followed was this one. He unplugged the cable going to the power board from the main board and the LEDs lit up, which was the same case with mine. I don't really understand what the issue with his TV was, but I think it was slightly different to mine anyway because his backlights were flickering before he unplugged that, whereas mine are completely off (until I unplug that cable, in which they all turn on).

I'm not sure what you mean when you said If the LCDs default to wide open do you see a full white image on the other side?
The LCD defaulting to wide open, not sure what that bit means. However when that cable is unplugged, the LEDs all turn on with no image, just blank.

I've taken an image of the back of my TV (see image here) and annotated it (see annotated image here) to help show my understanding of the basic inner workings.

I'm thinking of trying the power board replacement, but it sounds like maybe a better one to try might be the TCONs board instead if the LCD is troublesome, though I don't know.

 

[Eximo]

LCDs usually require power to produce black. The liquid crystals actually move to form light gates and control the amount of light going through each sub-pixel. But if there is nothing telling them what to do and they are getting power, perhaps the default mode is block all light.

What I was basically asking after is sort of what you may have narrowed it down to. If the TCON board is bad, then no timing signals exist for each sub-pixel to coordinate with. Simple digital logic would say that with no clock signal, they might do nothing even if they are receiving data.

 

[snodge182]

LCDs usually require power to produce black. The liquid crystals actually move to form light gates and control the amount of light going through each sub-pixel. But if there is nothing telling them what to do and they are getting power, perhaps the default mode is block all light.

What I was basically asking after is sort of what you may have narrowed it down to. If the TCON board is bad, then no timing signals exist for each sub-pixel to coordinate with. Simple digital logic would say that with no clock signal, they might do nothing even if they are receiving data.

That makes more sense, thank you for explaining. I have a feeling it could indeed be the TCON board, which hopefully is a cheap fix.

I did some more debugging and found some more info:
Unplugging one of the TCONs ribbon cable from the botton of the TCON board (the ones going to the screen), yielded different results. I unplug one of them, start the TV up and the LEDs come on and then dim, as they normally would. There was nothing on the LCD panel though. I tried this with the left ribbon cable unplugged while right is plugged in, and tried it the other way round too and both came with the same results.

I did notice during the test that when one is unplugged and the TV is on, there is a little blue light on the TCON board that lights up. The little light isn't on if both TCONs cables are in.

I took some photos: this is with both ribbons plugged in, this is with right one unplugged and this with left unplugged (no different to left) to help illustrate what I saw. Plus a close up of the LED here.

Does this info make any more sense of the possible issue? It's looking like it might be the TCON board but I don't know if it could also mean the boards that are attached to/part of the LCD could be going wrong.

Thank you again for all your help Eximo, it's looking like I may be able to fix this TV after all!