LG 42LB650V-ZN - no image, no backlight, there is a reaction to the remote contr

power supply: EAX65423701 (rev 2.0)
MB: EAX65384004 (1.50)

Good morning

I would like to ask for help on TV as in the subject.

The power supply has been checked, the voltages seem to be correct in standby mode, after switching on via the remote control or the button on the housing there is a reaction by a 3-fold attempt to start, it can also be seen on the voltages of 3,5,12,24 V reaching the mainboard. The voltages during the start disappear 3 times and appear so that they are finally constant and correct.
The TV reacts to the remote control, i.e. it can be turned off and on again, then the sequence of 3 attempts to turn on appears again.
The correct control signal from the board does not appear in the "Inverter ON" line, because after switching on only 0.075V appears. The signal from IC3000 (R5100GEAFB) is responsible for it, I also checked R2310 (1K) and R2309 (100) - it's ok,



I also made a reflow CPU, because I thought that IC3000 may be incorrectly controlled from the CPU - unfortunately no changes.


I have no ideas for further diagnostics on the lack of signal from INV_CTL so that the matrix backlight appears - it is still dark and there is no sound at startup, so the start sequence probably also does not start correctly.

I am thinking about reprogramming the memory, but I do not know if it is possible without removing it physically - is there any jtag or procedure to force programming from USB ??


greetings

Fix the backlight, don't go further.

In my opinion, this is the fault of the inverter or the power supply.

zbyniek82 wrote:

The correct control signal from the board does not appear in the "Inverter ON" line, because after switching on only 0.075V appears.

Can't force it? Yes to check the backlight?

I was surprised by GanCegall's first comment
there is no voltage from the LED power socket, the negative pole is missing,
when I check positive using mass from another point, I have about 105V
does anyone have a power supply diagram?

zbyniek82 wrote:

I have about 105V
does anyone have a power supply diagram?

Next to the socket is not printed how many?

is not printed,
I am surprised why I do not have a negative pole, next to it is the Q804 circuit, which probably does not give it, but what is it ?? I can't find the schematic for this power supply anywhere

zbyniek82 wrote:

is not printed,

Interesting, everyone is on, and yours is not, take a look again

zbyniek82 wrote:

I wonder why I don't have a negative pole,

And I am not surprised because you do not understand how it works and you do not want to understand it, although it is full of descriptions and diagrams.

zbyniek82 wrote:

next to it is the Q804 chip, which probably doesn't give it, but what is it ??

Yeah. It's hard to read the inscriptions on the disc, it's even harder after all on such a small element.

zbyniek82 wrote:

I can't find the schematic for this power supply anywhere

Because there is no.
But a little different, a little similar, to be found. You just need to be able to understand them.
In the meantime, read about the BD9486F in the forum.
Diagrams can be found in newer Philips PL14.x PL15, x.
I would give, but in this case I consider it a waste of time, because it is difficult to help someone who cannot see, does not understand.
You didn't even use the moderator's advice. It is true that you need to expand it a little, but you have your head.
And since you haven't used the other tips on the forum about backlighting, you can't do it, you will go round and round.
Especially if it turns out that INV_ON (and not only) actually does not exist.

As kol.mirex wrote.

Maybe start prosaically by checking the LEDs on the rulers
Otherwise

Quote:

PWM LED driver: BD9486F
MOSFET LED driver: MDD3752, 4NF20
LED driver (backlight): integrated into PSU; 206-208V 250mA
Power Supply (PSU): EAX65423701 (1.9) LGP3942-14PL1 P / N: 3PCR00439A
- MAP8800 (PFC), IC101 FA6A01N (PWM resonant) / * exchange for FA5760, NR134S SOP8
for matrix LC420DUE (FG)

It was for example in this forum link

Working principle ... ILed measurement (no BD system ...)



_________________________________________________________
This is the backlight in ver.32 "
- 3x 16LED or LED on 6V
** like ver. adapter on Vled = 140V

You would be one of the few who has something other than LEDs damaged in this model. Well, but there are things that "physiognomes don't dream about" as Ferdinand Kiepski says.
Turn on the TV, press the menu, shine the flashlight to the center of the screen, see if there are outlines of the square figures of the menu graphics.

zdzich42 wrote:

You would be one of the few who has something other than LEDs damaged in this model.

A fair point, in this model it is so, but maybe something has just started "falling" apart from the leds ...

gentlemen,

I would like to thank you from the tip. The forum is also for beginners and I am, although your tips are at a very professional level,
As soon as I test the directions you indicate, I will let you know immediately.
Mr. "mirex", everyone learns from their mistakes, in fact I also made a mistake here writing that there is no voltage mark, but I would ask for forgiveness for the "weak". For some, some topics are obvious, for others not, everybody starts their adventure with electronics, and criticism is also valuable! This forum is an encyclopedia that can sometimes lead astray and sometimes indicate the direction that must be taken, for which I thank everyone involved



greetings

lisek wrote:

As kol.mirex wrote.
Maybe start prosaically by checking the LEDs on the rulers

That's what Colonel Gancegall wrote early

GanCegall wrote:

Fix the backlight, don't go further.

and also a respected moderator:

bogred wrote:

Can't force it? Yes to check the backlight?

This is called favoring the "system"

Maybe it will help: when I pull out the cable from Inverter ON (only one cable from the plug) and turn on the TV, the backlight starts. for that I have no tension on TCON heheh what would I not do.

tezewiusz wrote:

Maybe it will help: when I pull out the cable from Inverter ON (only one cable from the plug) and turn on the TV, the backlight starts. for that I have no tension on TCON heheh what would I not do.

A colleague is right it is not damage to the diodes, but to the motherboard.

I confirm that the diodes were OK,
The disc was damaged, unfortunately I did not find specific damage. I ended up replacing the entire disc

greetings

zbyniek82 wrote:

I ended up replacing the entire disc

Regards

The whole album ... and everything is clear.
greetings too