Samsung UN40H5203AF LED backlight out

[lordkev]

Hi, I'd appreciate any help. Bought a non-working Samsung UN40H5203AF LED TV today. I've done the flashlight test and I do get a picture, but the LED backlighting doesn't come on. I've also tried disconnecting the main board from the PSU / LED driver and they still don't come on.

It seems likely to be either the PSU or a blown LED, but I'm not sure which.

Here are the voltages measured on connector CNL802:

1 D+ (no wire here): 209
2 D+: 209
3 S1-: 57
4 S2+: 57
5 NC (no wire here): 0
6 S2-: 30
7 S3+: 29
8 D-: Started at 40 and steadily dropped until settling around 23
9 D- (no wire here): Started around 60 and steadily dropped until settling around 19

[budm]

Re: Samsung UN40H5203AF LED backlight out

Looks like open connection to the LED assembly or bad LED (open circuit).

[lordkev]

Re: Samsung UN40H5203AF LED backlight out

Do you know how I get at them to replace them? (If I'm able to find replacements)

I've tried searching all over and haven't been able to find any disassembly instructions that go down that far. I tried taking the front bezel off and with the panel separated I could see them behind the diffuser, but going through the front didn't seem to be the correct way.

[budm]

Re: Samsung UN40H5203AF LED backlight out

You have to go through the front, the frame has come off, the LCD glass panel has to come off which is the most delicate piece, then the diffusers, etc.
You should practice on the broken panel first if you have never done one before.
I do not know if your panel is edge lit or backlit and you do have to tools to do the LED replacement or not.
https://www.badcaps.net/forum/showthread.php?t=46403

[victor_cj]

Re: Samsung UN40H5203AF LED backlight out

Guide yourself from my pictures, different model.

[thoma]

Re: Samsung UN40H5203AF LED backlight out

Is there a servicemanual or training available?
regards thoma

[lordkev]

Re: Samsung UN40H5203AF LED backlight out

Guide yourself from my pictures, different model.

This one is backlit instead of sidelit, so it's a bit different. I'll get it figured out though.

Thanks for the pictures

[lordkev]

Re: Samsung UN40H5203AF LED backlight out

You have to go through the front, the frame has come off, the LCD glass panel has to come off which is the most delicate piece, then the diffusers, etc.
You should practice on the broken panel first if you have never done one before.
I do not know if your panel is edge lit or backlit and you do have to tools to do the LED replacement or not.
https://www.badcaps.net/forum/showthread.php?t=46403

This looks very similar to how mine is setup. Thanks!

[lordkev]

Re: Samsung UN40H5203AF LED backlight out

Ok, a little more diagnostic info. I was able to get to the strips. There are 3 LED strips. All the LEDs appear to be lit, but extremely faintly. Have to put a towel over my head to see them.

I measured about 120V across the top strip, but only ~17V across the middle and bottom strips.

Also, at one point I accidentally had my meter in continuity/diode test mode instead of voltage when connecting across the +/- terminals on the first strip. The middle and bottom strips immediately lit up to full brightness while I did this.

[budm]

Re: Samsung UN40H5203AF LED backlight out

Looks like the top strip has high resistance.

[lordkev]

Re: Samsung UN40H5203AF LED backlight out

This is really strange. I swapped the top and bottom LED strips which appear to be the same, and BINGO all the backlighting turned on. We'll see if it lasts, but for now I'm a happy camper.

[tom66]

Re: Samsung UN40H5203AF LED backlight out

H series set, isn't this TV less than a year old?
Samsung might cover it under a warranty program.

[budm]

Re: Samsung UN40H5203AF LED backlight out

This is really strange. I swapped the top and bottom LED strips which appear to be the same, and BINGO all the backlighting turned on. We'll see if it lasts, but for now I'm a happy camper.

May be the connectors are not seated properly?

[ziddey]

Re: Samsung UN40H5203AF LED backlight out

This is really strange. I swapped the top and bottom LED strips which appear to be the same, and BINGO all the backlighting turned on. We'll see if it lasts, but for now I'm a happy camper.

Hah. Is your TV still working? Picked up the same model today with exactly the same results as yours. Saw a burn mark on the top strip.

Swapped it with the bottom, and sure enough, all the LEDs are evenly lit. Individual LED resistance seems to be all over the place though.


Update: Welp, either the original owner damaged the ribbon cable or I did. Screen was working except for one vertical line (can still be seen in perfect black) on the left side. I fidgeted with the ribbon while it was on (dumb) and burnt my finger / saw the ribbon fry.

What a shame.