Samsung un55hu7250f no backlight, has picture and sound

[hasun100]

I have a curved 55' samsung UN55HU7250F with powerboard BN44-00781A, with no backlights coming on. I did the flashlight trick and I can see the menu etc and I hear sound. I removed back cover and disconnected Main board connector CNM803 and power back on but back lights still didnt come on. I did some voltage testing on the CNL802 connector with the L.e.ds connected and not connected and not sure if voltage is right or if i am doing the right test on some of the pins such as n.c? (see below)
At this point im hoping its the board that way I dont have to remove the curved glass and risk cracking it Or maybe there is a way I can apply voltage at the cnl802 connector and see if the lights power on? Any help is appreciated guys!

CNL802 Volt test

1-N.C - NO WIRE
2- 2+ - 230-240V - SAME READING LED CONNECTED OR NOT
3- 2- - 95-100V - DROPS TOO 0.10V WHEN LED NOT CONNECTED
4-N.C - NO WIRE
5-N.C- - NO WIRE
6-N.C - 0V
7-N.C - 0V
8-N.C - NO WIRE
9-N.C - NO WIRE
10- 1+ - 235-240v - SAME READING LED CONNECTED OR NOT
11- 1- - 0V
12- N.C - NO WIRE
13- N.C- NO WIRE
14- N.C- NO WIRE
15- IF2 - 0V
16- IF1 (BLUE CABLE) - 0V

[budm]

Re: Samsung un55hu7250f no backlight, has picture and sound

'11- 1- - 0V' You have open circuit in LED string #1.
Samsung BN44-00781A

[hasun100]

Re: Samsung un55hu7250f no backlight, has picture and sound

thanks for the quick reply, is there a way I can confirm this without taking panel apart? and how can we make sure its not actually the board not giving that voltage because its the same reading with led plugged in or not...

[budm]

Re: Samsung un55hu7250f no backlight, has picture and sound

You can swap the #1 and #2 pair of the LED wires to see if the problem will follow or not. The problem can be open connection on that LED connector that goes to the power supply board, open wire, open LED, open connectors on the LED strips. Open circuit does not automatically mean bad LED, open circuit can be any thing in the current path.
The 1+, 2+ are the Anode pin of the LED strips which the boosted LED drive Voltage is connected to, the 1- & 2- are the Cathode return line for the LED strips.
2+ you have Voltage feeding and you also have Voltage coming out of it but #1 is not working.

[hasun100]

Re: Samsung un55hu7250f no backlight, has picture and sound

Took apart the screen and found a loose connector on the top LEDs, you we're right!

Thanks for all your help, now i feel confident doing this in the future to any tv!

[Wilderone]

Re: Samsung un55hu7250f no backlight, has picture and sound

Well done 👍

[budm]

Re: Samsung un55hu7250f no backlight, has picture and sound

Thanks for the follow-up on the repair.
BTW, did you inspect all the connectors?

[hasun100]

Re: Samsung un55hu7250f no backlight, has picture and sound

Yes I double checked all the connectors to make sure! TV is doing good so far.

Thanks again for your tips and help!