Samsung UE50TU7005KXXC

[Puuhis79]

Hi,

Im looking for schematic for mainboard, I have issue with backlight. It is totally dimmed. Or any tips to check or where to find even close schematic




Pete

[nomoresonys]

Can you detect anything on the screen with a flashlight or when you hit menu? If you can, turn off all eco mode and ambient settings, auto brightness etc. Do a simple reset, unplug tv from power, hold power button on tv down for 30 seconds replug and try it, reset probably won't work in this case but doesn't hurt to try.

[EazyBone]

What you need is a led tester which is like $20 to confirm it's not your LEDs that are out .. not sure why you would think it's the main board immediately

[Davi.p]

Watch the square alluminum heatsink on bottom right, the transistor Q90001C pins have something white dripped onto pins.. check it.. check also output pins voltages, every one.. report them with pin name..

[Diah]

What you need is a led tester which is like $20 to confirm it's not your LEDs that are out .. not sure why you would think it's the main board immediately

this is all in one the joke cheat boards made by Korean... they stole the method from other brand... and they did faked the parts installed on boards with fake No or name...

OP. give up you will never put yours hand on any documents or parts as all fake name.

[Puuhis79]

thanks for info,

White stuff is glue or something, I removed it to measure mosfet... LED tester is ordered to check is it mainboard or the strips... lets see..... Il do measurements for led connector, to see if its shorted or missing voltages..

These "all-in-one" boards are pain in the *** but let not give up with out trying...

[nomoresonys]

Gave a suggestion, no response, not wasting time on people with no common courtesy.

[EazyBone]

Don't use led tester while it's plugged into the board. Remove the connector and test, or on some Samsungs you have to remove the board to tedt

[Puuhis79]

Don't use led tester while it's plugged into the board. Remove the connector and test, or on some Samsungs you have to remove the board to tedt

Thanks for the tip, made some mesurements from led connector…led strip can be the faulty one… lets see when tester arrives

[Puuhis79]

Can you detect anything on the screen with a flashlight or when you hit menu? If you can, turn off all eco mode and ambient settings, auto brightness etc. Do a simple reset, unplug tv from power, hold power button on tv down for 30 seconds replug and try it, reset probably won't work in this case but doesn't hurt to try.

Sorry for late reply, I can see image with flashlight, all settings are ”factory default” still image is dimmed.
and yes I tried power cycle 30s trick, but no help.

[nomoresonys]

I'd be confident enough to tear it down to backlights and check them with a multimeter at this point, I see you ordered a tester. Might as well wait since it's already coming. Pardon my snap, I jumped to judgement.

[Repairtechlcd]

Most probably you have faulty backlights, Check the voltage on pin 8 of CN801 on switch on and see if the voltage rises momentarily and then falls .If so it is definitely the backlights. The are 3in1m sets ,this concept is very popular with TVs made in China although I believe this set is made in Vietnam.

[Davi.p]

Very low diagnostic level here, so it turns out that you have backlight off, not.very dimmed as for the first post.. no tv set consent to dim the lights to zero, anyway you tested the outputs but until you don't post the result the request for help is no useful, also testing the cathode of the big secondary diodes can be helpful to find a feedback problem/low voltages.. i haven't managed to know until now if that Samsung jelly glue is of help or not..

[Puuhis79]

Ok,

Status update, voltage for leds rises, during the stratup, but it stays... so I will dissassemble more to see led strips...

[nomoresonys]

I believe you misunderstood post #12. What exactly is the voltage that it rises to and stays at?

[EazyBone]

Ok,

Status update, voltage for leds rises, during the stratup, but it stays... so I will dissassemble more to see led strips...

You mean with the tester? I think we are both confused. I've never confirmed backlights issue with that gues method before. Using a multimeter?

Tell us what exactly you did

[Puuhis79]

So,

I was using multimeter, voltages are around 260V DC, and stays, so it seems that led strips are dead... I ordered new strips... i will dissassemble more to check what went wrong with the strips...

[Puuhis79]

Update!

So, with further investigation, I find strange things, Led strip voltage was 260 without the load (led-strips), when load was put back -> voltage to 0V. Led strips were tested with LED tester, it showed 100V and very dimmed light. Next I scoped/measured pins of control IC for Led backlight (SM1251), IC is getting 12V, but output for Mosfet is only few mV -> So after changing SM1251 -> output is 13.5V for Mosfet and voltage for ledstrip is 125V (loaded), but still backlight is dimm, no help from settings (thru menu -> brightness etc.) I decided to change led strips -> DONE -> TV works fully OK!!!

[CapLeaker]

Update!

So, with further investigation, I find strange things, Led strip voltage was 260 without the load (led-strips), when load was put back -> voltage to 0V. Led strips were tested with LED tester, it showed 100V and very dimmed light. Next I scoped/measured pins of control IC for Led backlight (SM1251), IC is getting 12V, but output for Mosfet is only few mV -> So after changing SM1251 -> output is 13.5V for Mosfet and voltage for ledstrip is 125V (loaded), but still backlight is dimm, no help from settings (thru menu -> brightness etc.) I decided to change led strips -> DONE -> TV works fully OK!!!

This was more of an unusual case. Good job!

[Davi.p]

I don't remember the schematic but this is a typical case, led circuit broken togheter with the control IC, thank you for instising in the job and posting back results, not as many other people does, this is the classical case that demonstrates my theory is ok that led strips are damaged mainly by power surge/ transients, not as the stupid techincians in italian forums said (bad quality led or overloaded leds, these disaminations make me laugh...)
bye and compliments..!