Samsung QN55Q70AAFXZA Half Screen Dim

[Tom C]

I’m working on a Samsung tv for my son. When I brought it home the left side of the screen was dim, right side ok. I’ve replaced the LED edge strips, main board and now the power board. The only difference is that the dim side has switched from left to right. Is there something else I should be looking at? I’ve also replaced the ground tape (Faraday tape?) from the LCD screen to the chassis. I probably have a week left on returning the parts.
Any suggestions would be appreciated.
thanks.

[EazyBone]

Seems like you replaced everything.

So it looks like you have to break down again to see what's going on but with Samsung you unclip the main board from the power board and when you're all the way down to the lights you plug in the power board and the lights will turn on. You can then check and see if there is something not connected properly if the lights don't turn on. You can also do this without breaking everything down just disconnect the main board from the power board and plug it in and the lights on both side should go on. Try the old power board as well and see it both sides go on..

When putting the diffuser on again if you push too hard against the LEDs or if you're pushing the LEDs too hard in general they will break as there somewhat delicate so you may have broken some of the LEDs and that's why the other side is now out. Likely you will have to tear down the whole thing again but don't put it back together until you get both sides to light up all the way down at the LEDs.

Loose connector or bad power board or the LEDs are damaged again these are the problems most likely. I would bet the LED got damaged when putting the diffuser screen back on or you forgot to clip that side of the screen

[Davi.p]

But they makes again the full led / direct led? i always read about these poor edge leds..

anyway check. power board schematic table of pins towards main board and report here..

try to do a service mode factory reset..

[nomoresonys]

Try a factory reset if you haven't already.

[Tom C]

Thanks for the replies.
I haven't done the factory reset yet, but did update the firmware.
Just for clarification, both sides light up, one side is dimmer than the other.
I did unplug the main board and both sides light up, right side is dimmer than the left. I'll replace the original and re check.
It’s the dim portion switching sides that has me wondering.

[nomoresonys]

Indeed, that is strange, don't think I have seen that before.

[Davi.p]

the strips are vertical? did you do a Magician number but put an original one for error? Are the strips identical or specular?

[lotas]

BN96-52584A

[EazyBone]

Picture is like this now yes?

This is a all white background that I put on.

If it is, my bet is a damaged led on installing. I've done this on e before and I went took off diffuser shield and sure enough one was stuck to the diffuser when I pulled it off.
Originally I missed you saying it works but dimmer.. I think one was either damaged by you, or just came defective.

[Tom C]

This was the original problem. Now the same issue, but on the other side.
Any way to check the LED strips? They all seem to light when powered up.
Tomorrow I’ll be able to spend more time on using the suggestions I received.
thanks again.

[Davi.p]

can you swap the tcon>panel ribbon cables?

[EazyBone]

This was the original problem. Now the same issue, but on the other side.
Any way to check the LED strips? They all seem to light when powered up.
Tomorrow I’ll be able to spend more time on using the suggestions I received.
thanks again.

Led tester. Check voltage on each line with power board disconnected

[nomoresonys]

Well maybe it's a loose/bad connection where the backlights are connected to each other where one side was getting bad connection then somehow it improved and the other side side got loose??

[nomoresonys]

Also could be two leds just starting to fail, like maybe one on each side, causing this strange dealio.

[nomoresonys]

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

[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.

[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]

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

[Tom C]

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

[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