LG 55LF 5800 no video,no sound or backlight

[waybel]

The USBs are now closer to 1 mom and the hdmi are 2.8 mom

[lotas]

What are 1.8 and 2.8 Om, kOm, MOm?

[waybel]

the USB are all 1.8 the HDMI are 2.8

[lotas]

These are, from the processor side, relative to gnd.

[waybel]

[lotas]

Then take a high-quality close-up photo of where these ports are located.

[waybel]

Have you checked the usb and hdmi ports before heating the processor? If there is a short or low resistance on even one line, then the processor is no longer working properly. You can heat for 30-60 seconds.

I am not sure how or where to check the resistance

[lotas]

Have you checked the usb and hdmi ports before heating the processor? If there is a short or low resistance on even one line, then the processor is no longer working properly. You can heat for 30-60 seconds.

[waybel]

I removed the heat sink .I have a hot air/soldering station .How long should i leave hot air on at 385 degrees on the processor?

[waybel]

Yes i crossed the standby 3.5 volts to drive on and power on and got the backlights working

[lotas]

Well, here's the problem - motherboard, check the usb and hdmi ports for low or short resistance (signal lines), if they are ok, then heat the processor with a hairdryer (if possible, remove the radiator from it) and warm it up thoroughly without fanaticism for diagnostics.. .

[waybel]

Has 3.5 12 and 24 volts but has no voltage on Pdim1, p-dim2 or drive on.

[waybel]

no they are not.Top row are 3.5 12 24 volt

[lotas]

To start the backlight, the motherboard must supply these voltages to turn on the backlight driver, are they available?

[waybel]

Thanks to everyone and for the schematic .I am just learning and not great with schematics.I see the 89 volts i have going to both LED + .Obviously something is not turning them on to create the 215 and 145 volts needs to turn on the led strips.Any help appreciated on what to test/look for next

[lotas]

EAX65423801 schematic

[waybel]

Saw someone mention possibly BLO202B led driver on power board .Hoping it's not main board.Probably worth more than tv

[waybel]

No picture with flashlight that i could see.12 volts on T-con fuse.All voltages are good going to main board

[Storyteller12]

If I'm not mistaken these LG TVs “LF” series had problems with main boards. In particular the cpu overheats and goes bad. I don't recall anyone reflowing one to fix it either. Have to replace it unfortunately.

[EazyBone]

3 red light means TV is turning on. Lgs do this, not an error code.

Do you see a picture with flashlight? Turn screen on and look for picture. May take a minute or so before you see the no signal or the smart bar. Also check 12v on each side of TCON fuse.

Sometimes the main board is bad and doesn't send signal to turn on BL so test that first. Also give voltage readout on the PSU for each pin going to main board.