Samsung UN55KU6290FXZC no picture but backlight work

[pr0cess0r]

Il l i have this new project, when I connect the power it turn on and I see the backlight turning on but screen stay black. I did test the led with a led tester and they look same brightness with the tester they are not super bright.

Where should. I start??

Samsung UN55KU6290FXZC

[nomoresonys]

Re: Samsung UN55KU6290FXZC no picture but backlight work

check ALL voltages on connector, black probe on chassis metal ground, meter set to dc volts, red probe on each pin, check in standby[tv plugged in but not turned on] take note, leaving probes in place power up tv, take note, report both conditions as in, pin 1 off 0 volts on 13 volts etc, do it for every pin, example of testing there: https://www.youtube.com/watch?v=XH9GfkGQX1I

[pr0cess0r]

Re: Samsung UN55KU6290FXZC no picture but backlight work

Ok so here are the voltages and also of a picture i removed the heatsink and found a component that too me look like it is removed... hard to find picture of board without heatsink...

This is on im not able to turn it off... when i plug it without main board back light is brigther and then get lower.... with main board try to turn it off and play with menu i cant sse and it come bighth and then lower..

CNL802
1=267v
9=222v
other are NC or negative


CNM803
1=0.7V
2=3.1V
3=12.82
4=3.1V
5=12.82V
6=0.32V
7=12.82V
8=3.3V
9=12.82
10=GND
11=GND
12=GND

[lotas]

Re: Samsung UN55KU6290FXZC no picture but backlight work

Yes, you are missing the IC402 chip (BM81233MUV).
https://aliexpress.ru/item/100500308...00023978566910

[nomoresonys]

Re: Samsung UN55KU6290FXZC no picture but backlight work

ok i see, someone has been messing with it previously or did it come off with the heatsink, that would be unfortunate but a little funny, lol.

[pr0cess0r]

Re: Samsung UN55KU6290FXZC no picture but backlight work

so the person i got it from told be the mainboard needed to be replaced. is it common for this particular ic to fail on those tv?? should i look for a new board or it worth it to try to replace the ic?

[pr0cess0r]

Re: Samsung UN55KU6290FXZC no picture but backlight work

you are sure the backlights are on, can you see them glowing thru the holes in the back of the tv?

yes im sure they are on if i disconnect lvds cables the screen is all kind of blue and light on!

[pr0cess0r]

Re: Samsung UN55KU6290FXZC no picture but backlight work

ok i see, someone has been messing with it previously.

yes did not know to what point they messed with out but whne i saw the eatsink was not properly installed i know something was wrong and looked at it.

[nomoresonys]

Re: Samsung UN55KU6290FXZC no picture but backlight work

Probably the easiest route is a replacement board or a repair service you send your board to that will fix it up.

[nomoresonys]

Re: Samsung UN55KU6290FXZC no picture but backlight work

what is the version number of tv? usually found on back cover by the model number or full model number.

[diif]

Re: Samsung UN55KU6290FXZC no picture but backlight work

so the person i got it from told be the mainboard needed to be replaced. is it common for this particular ic to fail on those tv?? should i look for a new board or it worth it to try to replace the ic?

Do you have a hot air station ? The ic is much cheaper than a replacement board.

[lotas]

Re: Samsung UN55KU6290FXZC no picture but backlight work

This chip does not just burn out, but it burns out from a panel malfunction (something is shorting the power output of this chip, it can be VGH ....).

[nomoresonys]

Re: Samsung UN55KU6290FXZC no picture but backlight work

do you know how to test it Lotus?

[lotas]

Re: Samsung UN55KU6290FXZC no picture but backlight work

Look carefully at all the thin loops on the matrix where the decoders are located, if there are any burnouts on them.

[pr0cess0r]

Re: Samsung UN55KU6290FXZC no picture but backlight work

ok so i tested from pin 18 vgh and it is shorted to gnd... i looked aroung and there is an inductor L406 that is shorted to gnd on all 4 pin so i guess this is not normal?

DRP pin 14 is also shorted to gnd

this is with board out of tv


my model number is CJ05

[lotas]

Re: Samsung UN55KU6290FXZC no picture but backlight work

L406 and should be on GND (look at its pinout on the board).

Maybe you are lucky, ceramic capacitors can also short on the VGH signal.

[pr0cess0r]

Re: Samsung UN55KU6290FXZC no picture but backlight work

would it be a good idea to inject some power on the pin and see whta heat??

whe you say short on the matrix you talk on the flexible pcb?

[pr0cess0r]

Re: Samsung UN55KU6290FXZC no picture but backlight work

ok so i was all wrong google showed me a completly different part when i did my seach so i was on the wrong led and now it is impossible to find this part datasheet