Please LG TV no picture but sound slight buzzing

[Fixing222]

As shown on picture there is a buzzing from the small board I'm not sure what it is and there is sound when plugging in hdmi but just no picture any opinions will be helpful as I don't know. The red standby light etc all seem to work as intended and the sound
TV is LG-42ln578v

[nomoresonys]

Re: Please LG TV no picture but sound slight buzzing

Make sure tv is unplugged from power, leave the cable from tcon to mainboard plugged in, disconnect both ribbon cables from tcon to panel, the little black clips just flip up with a finger nail, never force anything, then plug tv in, turn on, see if buzzing is gone.

[Fixing222]

Re: Please LG TV no picture but sound slight buzzing

Make sure tv is unplugged from power, leave the cable from tcon to mainboard plugged in, disconnect both ribbon cables from tcon to panel, the little black clips just flip up with a finger nail, never force anything, then plug tv in, turn on, see if buzzing is gone.

Thanks i just ordered a T-CON BOARD i can ask for refund now it looks like led strips i guess i don't know thanks, if anyone has any ideas on the possible cause

[nomoresonys]

Re: Please LG TV no picture but sound slight buzzing

Yes, could be backlights, tcon or driverboard issue, really hard to tell without testing but I know not everyone has the tools or mindset to do the testing, there's some tests that don't require tools. Can do lots of testing with just a cheap digital multimeter from the big box stores.

[Fixing222]

Re: Please LG TV no picture but sound slight buzzing

Also wish i didn't get my Sony though something really heavy fell onto it and only caused the screen to scratch i was amazed also the colors seemed best, the features of it and how slow it is. So i like your display name lol.

Thank you i needed some advice like that a tcon is £3.80 where i live so might aswell try and then i will research if backlights is something it looks like i can do or cheap enough. Appreciated.

[nomoresonys]

Re: Please LG TV no picture but sound slight buzzing

Yes, good price for tcon, let us know how it goes, good luck.

[budm]

Re: Please LG TV no picture but sound slight buzzing

Thanks i just ordered a T-CON BOARD i can ask for refund now it looks like led strips i guess i don't know thanks, if anyone has any ideas on the possible cause

So did you did disconnect the cables between the panel and the T-CON to see if the buzz goes away? It may have shorted circuit in the tab bonding board, I would not try to test the new T-CON if the panel has shorted circuit.

[Fixing222]

Re: Please LG TV no picture but sound slight buzzing

So did you did disconnect the cables between the panel and the T-CON to see if the buzz goes away? It may have shorted circuit in the tab bonding board, I would not try to test the new T-CON if the panel has shorted circuit.

If the T-con is the one circled
Yes when i take one of the sides of the ribbon cables bottom right one the buzzing goes, leaving the bottom left cable in.
If i swap and put the botton right in it buzzes again.


So does it look like t-con or backights maybe do you guess?
Or from what i said the panel may have shorted and may not be fixable as i don't have experience in this

[budm]

Re: Please LG TV no picture but sound slight buzzing

If the T-con is the one circled
Yes when i take one of the sides of the ribbon cables bottom right one the buzzing goes, leaving the bottom left cable in.

If i swap and put the botton right in it buzzes again.
So does it look like t-con or backights maybe do you guess?

It means you have problem in the panel that is loading down the LCD bias SMPS power supplies when the ribbon cables are not connected between the panel and the LCD panel.

[Fixing222]

Re: Please LG TV no picture but sound slight buzzing

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[Fixing222]

Re: Please LG TV no picture but sound slight buzzing

It means you have problem in the panel that is loading down the LCD bias SMPS power supplies when the ribbon cables are not connected between the panel and the LCD panel.

Ok thank you for your help, so a new t-con or backlights are unlikely to work as i could then save on doing it

[Diah]

Re: Please LG TV no picture but sound slight buzzing

if the 12 Volts or the 24 volts hadn't more juice to let the TV run on.. then the buzzing will be heard, of corse no Screen Load no buzzing. advice you first to back to PWB and check all volts

[budm]

Re: Please LG TV no picture but sound slight buzzing

As shown on picture there is a buzzing from the small board I'm not sure what it is and there is sound when plugging in hdmi but just no picture any opinions will be helpful as I don't know. The red standby light etc all seem to work as intended and the sound
TV is LG-42ln578v

The Amplifier runs on same 12V power supply that runs the T-CON, so 12V power supply is fine.
You need to provide good close up of the T-CON board so we can start checking the Test points resistance.

[Diah]

Re: Please LG TV no picture but sound slight buzzing

as i know LG Amplifier runs on 24V .. ! i may wrong

[budm]

Re: Please LG TV no picture but sound slight buzzing

May be or mat be not but the Buzz is coming from the T-CON, not from the speakers. If power supply is badly loaded, the buzz should appear on the speakers also. Will find out more when he start checking the DC resistance on the T-CON board with all cables in place.

[Fixing222]

Re: Please LG TV no picture but sound slight buzzing

The Amplifier runs on same 12V power supply that runs the T-CON, so 12V power supply is fine.
You need to provide good close up of the T-CON board so we can start checking the Test points resistance.

https://imgur.com/a/7CffJoK

[budm]

Re: Please LG TV no picture but sound slight buzzing

Put all the cables back in place then start checking the resistance between chassis and those test points (VDD, VCC18, VIN, VGH, VGL, HVDD) I marked in the picture.
Make sure to report if the resistance are shown as in Ohms, K Ohms, or M Ohms. No power to the TV of course when testing resistance.
I cannot read the P/N as printed on top of IC U2 (LCD bias power supplies), please provide the numbers.

[petehall347]

Re: Please LG TV no picture but sound slight buzzing

back-lights coming on ?
did same side get scratched on screen as one that buzzing stops when ribbon disconnected. ?

[Fixing222]

Re: Please LG TV no picture but sound slight buzzing

back-lights coming on ?
did same side get scratched on screen as one that buzzing stops when ribbon disconnected. ?

No bacllight and my Sony TV was scratched but this one is fine not been scratched or.fell that I know of.

[Fixing222]

Re: Please LG TV no picture but sound slight buzzing


Managed to get better one with side angle
All displayed as k measurement on my UT118A auto select
VDD 2.295
VGH 8.79
VCC18 1.080
VGL 1.498
VIN 8.13
HVDD 1.135