crwdns2936637:0crwdne2936637:0 crwdns2853008:0crwdne2853008:0 crwdns2918746:0crwdne2918746:0

crwdns2933897:0crwdne2933897:0

Samsung tv with no backlight,only sound

Block Image
Block Image
Block Image
Block Image

I have an issue with my Samsung Tv, and i am losing my patience.

So no picture, no backlight, only sound

I already changed the tcon but its the same.

The weird thing is that the backlight comes on when i disconnect the cable that goes from the tcon to the board in the bottom of the screen, near the on off button, bottom center. But it comes on only when the cable is disconnected from the tcon. If i disconnect it from the other sides, no backlights.

So this is the status. I would be very happy if your experience would help here.

Thank you,

Klaus

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 1
crwdns2947414:01crwdne2947414:0

So i will answer for the last question and than i will measure. That cable comes from the led pannel, where it splits in two, and one side goes to the input board on the left (pic 1). I think that is the cable providing the power to the tcon.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

crwdns2934285:0crwdne2934285:0

crwdns2933315:06crwdne2933315:0

crwdns2934221:0crwdne2934221:0
crwdns2931211:0crwdne2931211:0 crwdns2931215:0crwdne2931215:0 crwdns2934225:0crwdne2934225:0
crwdns2934057:0crwdne2934057:0

crwdns2933897:0crwdne2933897:0

@klauskamberaj based on this "the backlight comes on when i disconnect the cable that goes from the T-CON to the board in the bottom of the screen" this could be an issue with the T-con board or (worst case scenario is that the panel is shortening out the backlight). At this time, I would replace the T-con board after making sure the ribbon cables are not frayed, corroded or otherwise damaged.

We totally understand this "i am losing my patience" and repairs like this can literally drive you up the wall, but it is not as bad as it all sounds. If you can, do this. Remove the back cover (after unplugging the power) and post a couple of images showing us all of the boards and their respective location and interconnect cables. Basically, just what it looks like when you remove the back cover. Then post some of all the boards separate. I know we can better troubleshoot your TV if we can see what you got going on there.

Adding images to an existing question - iFixit Repair Guide

Update (08/22/25)

@klauskamberaj the T-Con board is a beast :-) I've marked a few things to check. Main concern I have right now is fuse 2 is listed as a125V fuse. That is a high VDC voltage but I don't think this will be AC. Just be safe on it for now and don't necessarily touch it with your bare fingers. It's got to be DC....;)

I use the numbers I listed instead of the proper reference designators. It's just easier for me right now ;-) Hope those make sense. There are no voltages etc for F1 so check it for continuity. You can also check for voltage by trying to set your meter in VDC, black probe on ground and red probe on either end of the fuse. See what you get. F2 is the worrisome beast. Check for continuity and you can check the same way as previously described for voltage. Do the same for F3.

Now the red arrows just point to test points. So meter in VDC, black probe to ground (anything on the chassis will be ground if you have the board screwed to the chassis) and Red probe on the solder point. Let us know the voltages that you get on those points. Voff can be negative voltage so don't be surprised if it is.

Where does the connector with the red, white, black, yellow, green cable come from. Your LED driver board? Which cable did you disconnect to get the backlight to come on?

Block Image

crwdns2934105:0crwdne2934105:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 2

crwdns2944067:09crwdne2944067:0:

First of all, thanks for answering. You a legend!

So lets wrap it up.

The TV went red and immediately black. Sound was good.

I opened it up and i thought that the issue was with number 1 pannel, which i replaced today. Same symptoms.

Troubleshooting i noticed that 2 doesnt get warm, not a bit, so i think that there is a power flow issue somewhere. There is no visible damage or something burned.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

@klauskamberaj okay #1 is the LED Driver Board board #2 is the T-Con board. Try this. There are 2 ribbon cables on #2 that go to the panel driver boards (long skinny boards)

Disconnect the power

Disconnect one ribbon cable (either left or right) from #2 to the driver board.

Reconnect power

Turn TV on and let us know the result.

Next:

Disconnect power cord

Reconnect the ribbon cable

Disconnect the opposite ribbon cable

Reconnect power cord

Turn TV on and what do you get?

If the panel showed anything then the issue is with the driver board. That is kind of a PITA but we can possibly work around that.

If you have no change at all in how your TV behaves, it could be a T-Con board error. Do you have access to a multimeter? If so, we can check a few things on the T-con board.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

Hello. Just tried, didnt change anything. And yes, i have a multimeter here.

I checked the tcon for any visible burned or damaged component, but i cannot see anything.

I dont really understand how the power flow goes.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

@klauskamberaj do you have a board number or any other identifying markings on board #2? If not, can you post a close up (very close) so we can identify the markings and components on the board? We can get you to check some voltages on the board and hopefully that gives us a better idea. So far it all points to board #2 if it get's the proper signals.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

Sure. I attached it. The model is bn41-02492

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

crwdns2934275:04crwdne2934275:0

crwdns2934285:0crwdne2934285:0

crwdns2933897:0crwdne2933897:0

It sounds like you’ve already done some solid troubleshooting, Klaus. Since you’re still getting sound but no backlight, and the backlight only lights when the T-Con to main board ribbon is disconnected, that points away from the power supply/backlight driver and more toward a short or fault downstream — either in the T-Con itself (even though you replaced it) or more commonly in the panel/driver boards bonded to the screen edges. On Samsung sets this symptom usually means one of the panel driver ICs is dragging the panel voltage rails down; when you pull the ribbon, the load is removed and the backlights can fire normally.

crwdns2934105:0crwdne2934105:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 1

crwdns2947414:01crwdne2947414:0:

Hello.

Apparently i have changed the Led Board not the tcon. I guess this one is the issue, maybe a short somewhere

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

crwdns2934285:0crwdne2934285:0

crwdns2933897:0crwdne2933897:0

@klauskamberaj that confuses me slightly which may just be due to my age :-)

Just to make sure we are both on the same page. TV on, Black probe to ground and Red probe to either point of the fuse. You get 30VDC on one and 12V on the other?

Block Image

Now just the last clarification "when i disconnect the cable that goes from the TCon to the board in the bottom of the screen" which cable is that? For Samsung TV's one of the power board tests was to separate the main board from the power board which would then turn the backlight on. That was considered normal and showed that the power board as working normal

crwdns2934105:0crwdne2934105:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 0

crwdns2944067:04crwdne2944067:0:

So there are 5 visible fuses (pic attached), all of them showing 30v except F9006s which shows 12.5. I tested while main board cable is off, so all the leds are on.

Regarding the cable that i remove, is the one going from the led panel to the t con on the bottom of the tv. At first i thought that the tcon was the led pannel, thats why i wrote ot like that :)

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

Sorry, the second fuse is 12.5 not the third one. My mistake.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

@klauskamberaj that voltage seems to be to low. can you check the voltage on CN9002 BLU on? Test it with the TV off and then when you turn the TV on.

Also check the BLU voltage on the main board CN201 connector. Looks like pin 8 is it.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

Sorry i am not able to find the cn9002 pin? It should be a led stripe?

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

crwdns2934285:0crwdne2934285:0

crwdns2933897:0crwdne2933897:0
Block Image

sorry I meant CN9002 pin 3 If my eyes are not messing with me :-)

crwdns2934105:0crwdne2934105:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 0

crwdns2947414:01crwdne2947414:0:

It shows 4.13 after i turn it on and doesnt go down.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

crwdns2934285:0crwdne2934285:0

crwdns2933897:0crwdne2933897:0
Block Image

As far as i know and read online the tcon should use 12.5v and 9v, but i am not sure from where this current should come.

Apparently it doesnt come from the led board since max it produces 3.3v, so it should come from the stripes that come from the input panel.

Any info where the power should come at this tcon?

Ps. There is also a port but no cable comes to it.

crwdns2934105:0crwdne2934105:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0

crwdns2933897:0crwdne2933897:0

So after some more digging i found out that the power to turn on the tcon comes from the main board [red circle]. But there is no power emiting from there.

For now the tcon and the led pannel are not at fault.

Block Image
Block Image

crwdns2934105:0crwdne2934105:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0
crwdns2889612:0crwdne2889612:0 0

crwdns2944067:07crwdne2944067:0:

Yes, it is common for the main board to "tell" the power board to turn the backlight on. So a faulty main board can be the cause of no backlight. CN1801 also send the 13V to the PWM. Check pin 42-51. I just found the SM for a UE65KS9502T which appears to be pretty identical with your model. It has the listings of all the connectors and what signals they carry etc. Might come in handy to thumb through that. Ue65ks9502t Ue65ks9500t Maybe

Now this goes back to testing the fuses on the LD board.

LD Board/Panel Troubleshooting

1. Verify SMPS Vdrv 30 Vdc to LD Board (CN9001).

2. Unload the LD Board by removing the cables connected to CN9005 ~ CN9014.

3. Check the fuses on either side for approximately 30 Vdc (only when LD Board is UNLOADED).

- If voltage is 30 Vdc on all 5 fuses

√ Panel is likely defective.

- If voltage is low on any fuse

√ LD Board is likely defective.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

Good morning,

I already checked the manual. At LD the only fuse that its not 30v is the one 12. 5, which i guess its correct since it is shown on the board.

I also measured the pind coming from the power board to the main board, but i cannot follow the logic where the 13 volt stops. My best guess is that a component is shorted but no clue how to find it

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

@klauskamberaj The confusing part on this is that it stets that if the voltages are low on any fuse, it's the LD board (if you disconnected CN9005 ~ CN9014). In your case, that is a new one and we do need to assume it is a good board. You have no power going to the T-con board. CNT803 on the power board is connecting the LD board and the T-Con board. Now CN911 on the main board would send 5V to the LD board on pin 5. If none of those are present the issue will either be the power board or the main board. Since you have power to the backlights etc. when you dc the ribbon cable from the main board, it is unlikely that it is the power board.

Just out of curiosity, with everything put together and the TV on and you do have sound etc, shine a flashlight against the screen and see if you can make out any shape, or even your splash screen etc.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

Done that since day one. No image at all.

I found 2 fuses shortened in the main board.

Removed them and i was able to give 12.4 volt to the pin on the main board that goes to the t con. But at the moment that i connect the tcon, i have a short again.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

@klauskamberaj if this "But at the moment that i connect the tcon, i have a short again." actually blows fuses then the T-Con board would have a short on it. Once you replace the fuse on the main board again, can you measure the ribbon cable going to the T-Con board without plugging it in. See if the main board supplies the voltage up to plugging it in. Disconnect the ribbon cables going to the the screen and then plug it in. if the fuses still blow it'll be the T-con board.

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

crwdns2934275:02crwdne2934275:0

crwdns2934285:0crwdne2934285:0

crwdns2934229:0crwdne2934229:0

Klaus Kamberaj crwdns2934231:0crwdne2934231:0
crwdns2936625:0crwdne2936625:0:

crwdns2936751:024crwdne2936751:0 32

crwdns2936753:07crwdne2936753:0 156

crwdns2936753:030crwdne2936753:0 156

crwdns2942667:0crwdne2942667:0 156