LG 43UF7709 - Blinking Screen, No Picture, No Sound

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

I would try a replacement mainboard if reasonably priced, I'm not sure why the mainboard doesn't send the signal but it seems to be the problem in many failures.

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Usually that proves the backlights and powerboard are ok, looks like the mainboard is not sending the drv-on signal.

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Yes sir, connected Power on to 3.5 and drv on to 3.5 ans get backlights shining.

On power on and drv on i only get 3.29V. Should be okay i think?
But what does lightning backlight mean? Does the Mainboard have issues?

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Maybe try jump starting the powerboard WITHOUT mainboard connected, I think you use a 1k resistor from power on pin to 3.5 standby and another resistor from 3.5 standby pin to drv-on pin, then see if your proper voltages are there and if backlights come on. MAKE sure cable from powerboard to mainboard is unplugged for this test.

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Any other ideas?

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

I did unplug connector to mainboard but there are no backlight. Should i stay longer? I testet about 10sec.

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Unplug tv from outlet, unplug cable from powerboard to mainboard, plug tv back in out let, see if backlights come on and stay on.

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

So, i will List from Top to Bottom (i think top ist Pin1?)

LEFT ROW, TV PLUGGED BUT OFF
0V "SIN"
0V
0V
0V
0V
0V
0V
0V
0V
0V
3,5V
3,5V
0V
0V "PWR_ON"

RIGHT ROW, TV PLUGGED BUT OFF
0,055V "VSYNC"
0V
0V
0V
0V
0V
0V
0V
0V
0V
3,5V
0V
0V
0V "DRV_ON"

LEFT ROW, TV PLUGGED POWER ON
0,06V "SIN"
0,058V
0V
25V
25V
0V
11,68V
11,68V
11,68V
0V
3,5V
3,5V
0,73V
3,5V "PWR_ON"

RIGHT ROW, TV PLUGGED POWER ON
0,055V "VSYNC"
0V
0V
0V
25V
25V
0V
11,68V
11,68V
0V
3,5V
0V
3,5V
0,08V "DRV_ON"

@nomoresonys i hope you get what i mean, if not i will try to explain it better

@budm i think its the backlight. Blinking Screen is seen in front of the LG TV. If i stand behind, i dont see any white light from holes. It seems like TV try to turn on the screen but sticks in this mode.

EDIT/
I have to say, LD701 is blinking ORANGE not YELLOW^^

[budm]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Please provide good clear pictures so we can see what we are dealing with.
You say 'Blinking screen', are you referring to backlights are blinking?

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Test connector from mainboard to powerboard on powerboard side, test with tv plugged in but off then hit power, report both conditions here, give pin number, pin description and condition on and off.

[EUWest]

Hi everbody,

my LG TV 43UF7709 wont turn on. It only tries to show something, but it stays only blinking. So i removed the Backcover and first checked some Voltages.

I get on the powersupply all Voltages correctly, equal to the schematics nearby. The only thing i get maybe wrong is "LED+". On the Powersupply there stand it had to be 50V Output. I only get 38V on LED+. Could this be a failure?

Also there is a LED, LD701 which blinks 6 times in row YELLOW. What can this mean?

I also checked Powersupply out of the chassis. I couldn´t find any issues. But have to say, that i´m not a pro.

I also checked Voltage on TCON Fuse: I get 11,5V on each side.

What i noticed to is that the heatsink on the mainboard run very hot.

Would be have, if we can get this TV back to life