Samsung UE50TU7000K backlights on, no picture or sound

[notallbad]

Plug in and backlights with Smart Tv powered by Tizen logo shows on screen
then nothing, no stby led or response to remote, no sound from hdmi input.

This has only 1 board, a 3in1_kant_su2.

Try a usb stick with update firmware from Samsung and usb stick just flashes a couple of times, recognises usb, but thats it.

Remove ribbon to panel, same results.

I believe the leds are in an array of 3 x 12 @3v/led, going by what led sets are being sold for this tv on ebay and aliexpress.
1 string of 12 leds, power supply in 84v, out 54v, voltage drop 30v
1 string of 24 leds, power supply in 185v, out 84v, voltage drop 100v

which the string of 24 leds doesnt seem right!

Though still not ruling out bad panel or board.

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

Any thoughts on where to start with this one please.

[nomoresonys]

Re: Samsung UE50TU7000K backlights on, no picture or sound

maybe try the easier things first, test the diodes and resistors on top of the board if you have not already.

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

Ok. yh diodes and resistors seem fine.

[nomoresonys]

Re: Samsung UE50TU7000K backlights on, no picture or sound

maybe test QP811? on the heatsink, can't see the last number there, see if any of the legs test short to the other 2, may have to penetrate the glue with the probes to get a reading, see if any of the little mlcc ceramic caps are shorted or have very low ohms, test any voltage regulators, maybe check the pins on the connector of the panel driver board, thinking there should be 12 volts on one when working properly. Can test the panel driver board test points VGL etc.

[diif]

Re: Samsung UE50TU7000K backlights on, no picture or sound

No, if you think about that is happening, the TV shows a picture, it's not power components or the panel.

Maybe LEDs, that voltage doesn't seem right.

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

ok this is what someone is selling on ebay for exact same tv, I believe.

The red connector goes to power/main 3in1 kant board, then there are 3 led connectors, 2 of which have shortish leads between them so guessing they connect to the full array set of leds, all 36 leds (3 strips of 12/strip), which makes sense according to the voltage reading of 100v drop which would be enough for all 36 leds, 36 x 2.7v= 97.2v, but the 3rd led connector has a very long lead so must go elsewhere, edgelit too perhaps? puzzled here!

only way to know for sure is expose the leds but really only want to do that as a last resort for obvious reasons.

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

I cant see any obvious signs/presence of edgelit from the rear panel, only see where there are 3 led strips so my best guess is that this panel has more leds than 36.

[vinceroger69]

Re: Samsung UE50TU7000K backlights on, no picture or sound

.

[nomoresonys]

Re: Samsung UE50TU7000K backlights on, no picture or sound

well its not an old tv but anything can be wrong from a bad/weak cap to backlights, I would tear it down and check, seems more time consuming but I usually get it done faster than I can test everything else, with panels about 55 or less that is, still need to treat those panels like a newborn, they are all easy to break.

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

ok thanks for help but not going to waste anymore time on this so going to trash it.

Too expensive to buy a 2ndhand board only to find its the panel afterall, which I think it is to be honest.

[Storyteller12]

Re: Samsung UE50TU7000K backlights on, no picture or sound

It’s most likely the panel. A lot of the nu, tu and ru series have panel issues. You can try the tape method since it’s free and wont cost anything.

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

Attempted the cut-off method but no luck getting any kind of image on the screen. Possibly not getting the correct pins blanked off.

Removed the panel to look at the backlights, all appear to be working, however the connector between 2 of the strips was not getting a good connection so linked them across to give a good connection before reassembly.

Still no difference! except the Smart tv powered by tizen logo on powerup is much brighter and clearer.

The led connector at psu/main board has 4 wires, 2 wires go to the bottom strip (12 leds) and 2 wires go to the top and middle strips (24leds).
With the led connector removed there is 244v going to the top/middle strips but nothing on the other supply pin.
Plugged back in theres 167v in 95v out on the 24leds and 95v in 65v out on the 12leds.
The 95v output voltage from the 24leds is fed back into the 12leds from the 3in1 board.


This is for info really I suppose but still hoping something comes to light and can get it working again.

I am still of the opinion that there is a fault on the 3in1 board. It powers up as soon as its plugged in, no picture other than the startup splash logo and no audio.

There is response from the remote, well the led flashes when the remote is operated vol up/down etc.. think it probably was all along, just that I never noticed it as its underneath the panel and not easy to see.

[nomoresonys]

Re: Samsung UE50TU7000K backlights on, no picture or sound

well test all the components, can also test the panel driver board ala post #5.

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

Voltages around the main board all seem present and ok from what I can see.
On the panel boards there are 2 banks of 6 M35 transistors which have a voltage switching between -11v and +30v, is this normal?

Theres a -11v on the main that stays constant, VOFF_-11V_PW.

[Rajnhl]

Re: Samsung UE50TU7000K backlights on, no picture or sound

Voltages around the main board all seem present and ok from what I can see.
On the panel boards there are 2 banks of 6 M35 transistors which have a voltage switching between -11v and +30v, is this normal?

Theres a -11v on the main that stays constant, VOFF_-11V_PW.

its normal
no sound and pic check for firmware

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

If I hold power button on remote tv does restart.

If i press info menu mute power it restarts but dont seem able to do a reset. even though doing it 'blind".

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

Log on usb stick when attempting upgrade from samsung website

SES path not found, exit

[vinceroger69]

Re: Samsung UE50TU7000K backlights on, no picture or sound

Log on usb stick when attempting upgrade from samsung website

SES path not found, exit

https://us.community.samsung.com/t5/...b/td-p/1700823

[notallbad]

Re: Samsung UE50TU7000K backlights on, no picture or sound

Found ver2400.9 but still the same, ses path not found.