LG UHD TV 49UF7787 webOS

[angel-boy]

hy , i have a problem with LG 49UF7787 :
- when power on , red led flashing and stops, but is no image, no backlight. If i press power button again, the tv powers off
- i thinks is a software problem, but cannot update firmware.

Any help ?

[dick_barton]

Re: LG UHD TV 49UF7787 webOS

Have you any photo's of your boards and taken any voltage readings?

[angel-boy]

Re: LG UHD TV 49UF7787 webOS

power LG EAX66306501 (2.0) , have a led , it`s flashing 7 times , for few series , after that 5 flash ( the led top flashing if i give 3.4v to drv_on )
main EAX66387003 2.0

voltage

with the tv off i have 3.5v

with the tv on , i have
pwr_on 3.4
p-dim 3.4
p-dim2 3.4
drv_on 0.077 ( i give here 3.3v , and have backlight but white screen , no image from mainboard.)

in rest i have 3.4 , 12, 24v

[dick_barton]

Re: LG UHD TV 49UF7787 webOS

If you have all the voltages, 3.5V, 12V & 24V then it looks like the problem is with the main board not sending out DRV_ON to the power supply.

[angel-boy]

Re: LG UHD TV 49UF7787 webOS

i give 3.5 to DRV_ON, i have backlight, but no image,

the problem is with mainboard. any idee how can i make a firmware update ? like vestel press ok and conect to power etc.

[Andrew F. Ali]

Re: LG UHD TV 49UF7787 webOS

Check the SMD fuse on the T-CON Bd. if there is 12Vdc on both sides or before you put the power on, if the fuse has continuity and not open.

[moateez]

Re: LG UHD TV 49UF7787 webOS

teste the voltage of backlight

[angel-boy]

Re: LG UHD TV 49UF7787 webOS

Check the SMD fuse on the T-CON Bd. if there is 12Vdc on both sides or before you put the power on, if the fuse has continuity and not open.

is good, tested

[angel-boy]

Re: LG UHD TV 49UF7787 webOS

teste the voltage of backlight

the backlight is working , if i give manual 3.4 v

[Andrew F. Ali]

Re: LG UHD TV 49UF7787 webOS

If the Main Bd. does not produce the DRV-ON signal and you have powered it externally and you have the 12Vdc on both sides of the T-CON SMD fuse, my only thought is that the DRV-ON signal derived on the Main Bd. that is not being produced not producing LVDS signals to T-CON. If you have a scope you could check to see if the Main Bd is producing the LVDS signals.

[angel-boy]

Re: LG UHD TV 49UF7787 webOS

So where to check first , and what to check , i dont have tester for signal from main.

[peterkos2]

Re: LG UHD TV 49UF7787 webOS

Good day. I have the same problem with the LG 58UF8307 TV. Can you help me? Has anyone solved this? Thank you for your response.

[nomoresonys]

Re: LG UHD TV 49UF7787 webOS

If you have the exact same symptoms and you checked what he did, as in no voltage on drv-on pin, it's very likely a mainboard issue.

[peterkos2]

Re: LG UHD TV 49UF7787 webOS

Yes, I have it confirmed, can something be done with that board? What could be the problem?

[nomoresonys]

Re: LG UHD TV 49UF7787 webOS

Maybe a very well done do it yourself reflow of the bga, can check youtube for procedure, of course some will have a good technique and some won't. Maybe someone here can guide you. My best advice is if it does work, try to get a fan blowing on it when the tv is on, to try to keep it cool, which will make the "fix" last a lot longer than without one. Maybe someone can chime in on how long theirs has lasted with a fan solution.

[peterkos2]

Re: LG UHD TV 49UF7787 webOS

Maybe a very well done do it yourself reflow of the bga, can check youtube for procedure, of course some will have a good technique and some won't. Maybe someone here can guide you. My best advice is if it does work, try to get a fan blowing on it when the tv is on, to try to keep it cool, which will make the "fix" last a lot longer than without one. Maybe someone can chime in on how long theirs has lasted with a fan solution.

well thank you
Yes, I tried it - the image started for a few seconds and then disappeared
Then I tried several times, but without success.
So the mainboard will have to be replaced.