Samsung QN55Q70AAFXZA Half Screen Dim

[Tom C]

Yeah, but I still enjoyed the challenge, learned something and found this forum. Win all around.

[nomoresonys]

Well at least it was only a samsung, might be the best that could happen...Lord only knows how much trouble that tv could have caused you.

[EazyBone]

Rip tv. Hey you learned something. I cracked the first 3 tvs I got and since then never again. Gotta learn somehow

[Tom C]

The white/blue are in pairs (clear/yellow) as seen in the photo. I now know from, thanks to this forum, to power up the LEDs before reassembly.
Unfortunately, while moving the LCD panel, I cracked the corner. Pretty sure that’s the end for this TV.

I want to thank all who helped me with this project and am looking forward to being part of future discussions.

Tom

[EazyBone]

Blue LEDs are used for QLED tvs. They use blue LEDs and a yellow diffuser

[Davi.p]

OK,, strange design, i don't know why blue leds, maybe they lit or not depends on the user settings..

[EazyBone]

Yea now you know, always plug in TV before setting it back up to test the strips. Always disc main board from PSU before doing so, on Samsung anyway.

IF you remove the only blue strip and plug it into the other connector... And plug in see if it lights up only blue still with other connector. Maybe? I may try just to see

[Diah]

can you upload high quality photo of the PSU from the top and down side ?

[Tom C]

Yes, you are correct. H is for the white light, L is for the blue.
Original set are the same part number for each side. Of the original pair, one side lights only the blue, other both white and blue. The blue only strip was defective.
I usually buy tv parts from Shop Jimmy, but they didn't stock the edge strips I needed.

[lotas]

The correct 4 contacts are H+ and H- (this is the power supply for the bright ones) and L+ and L- this is the power supply for the dim LEDs.

[Diah]

L - LOW
H - HIGH
Most likely one LED has two LEDs (one for low light (playing the role of darkening), the second for high light.

+10000

[Davi.p]

I don't think, i see the photo, only 4 pins per strip, 2 for leds, 2 for sensors

[lotas]

L - LOW
H - HIGH
Most likely one LED has two LEDs (one for low light (playing the role of darkening), the second for high light.

[Davi.p]

I think you reported bad the power b. pins measurements, my guess is that the L is the leds line, but the H is the light sensors to the side of leds, this last is the problem, thus why the light feedback is wrong on one side? my guess is that the assembly job of the leds strips and fresnel sheets positioning puzzles the light feedback..

ps: normally edge led strips broken in two parts are specular thus not same part

[Diah]

i think yours issue at the hard first Reflector plate see the surface which it contact with LEDs... if there any yellow,,,
at time you put it back you just put it in 360 degree so the dark one become on the other side

[Tom C]

Thanks EB. Unfortunately I got them off eBay and will have to contact the seller.2

[Tom C]

Opened it up and one side is brighter than the other.
The part numbers are different on the strips. 🙄

[EazyBone]

Values are likely fine. It's not the panel it's the lights. Something is wrong with them. You got defective ones or something is broken. Bad connection, something. At least the most likely thing. I would snap a picture and get a new set from who sold them to you

[Tom C]

I figured I should start from the beginning and reinstalled the original boards.
Checked the original edge strips with an LED tester and measured 176 V on the H+, H- and L+,L-.
Powered up and did the factory reset and then disconnected the main board and there's no change.
Used LED tester on the new edge strips from the pins on the power board, 172 VDC.
Measured DCV at the pins out to the edge lights on the power board and have the following:
Pin. Desc. DCV
1. 1H- 94.4
2. 1L- 94.4
3. 1+ 282.4
4. 1+ 282.4
5. 2H- 94.5
6. 2L- 94.3
7. 2+ 282.4
8. 2+ 282.4
9-12 NC +/- 2

The values look consistent, but I don't know what they should be.
Is it possible the issue is in the LCD panel or the address (?) boards? I'll post more after I disassemble the unit.
thanks again.

[nomoresonys]

Maybe turn the backlights way down, see if you have the same thing.