No audio no video no backlight on LG47LX9900

[Ashish_Jamesh]

Hi I have LG47LX9900. Accidentally it stops with some short circuit sound. I disconnect it from main power and restart again after 10 minutes. Tv was turning on and respond on remote signals but there is no audio, no video and no back light from it. I asked local technician too see these problem. He said that I have to replace Main AV Board. So I bought new AV Board from Ebay.co.uk. And after replacing the new board I still not have audio and video from LED. So I again contact my technician for this issue now he said that the next step for this problem is to replace T-con board. So I bought new one from Spares2Repair.co.uk. Now I replace the T-con board and turn the tv on with LVDS cable connect only T-con side (I accidentally broke LVDS pins so I reset all pins) . After 2 time restarting the tv in morning I got back backlight and display in half screen size with verticle bars and half side completely black. All led light strips working fine. But at evening I try again to power on the screen but again no audio, no video, no backlight. I try all way but nothing happen. TV respond on remote signals, gives clicking sound on startup but without audio video.

[dick_barton]

Re: No audio no video no backlight on LG47LX9900

Can you provide a picture of what was broken?

[Ashish_Jamesh]

Re: No audio no video no backlight on LG47LX9900

Pic no.4 shows damaged pins of LVDS cable..I searched for LVDS cable but not found in local market so i cut down the broken lvds cable and trim it and make new pins. after attaching this new modified cable i still not got display. But after removing the cable from Mainboard side I got backlight and display in half left side with half dark black right side. So i thought i will look after this at evening. but at evening when i turn on the tv like in morning but surprisingly i didnt got audio, video and backlight.

[Ashish_Jamesh]

Re: No audio no video no backlight on LG47LX9900

members please reply on my thread if its possible for you.

[dick_barton]

Re: No audio no video no backlight on LG47LX9900

Start from the very beginning. You have several connectors and you need to take the voltage reading on each pin of the connector, The connectors will also have names so you need to supply the following information. A clear photo of the power supply board showing the connectors and pinout legends would be helpful.

Example Voltage read on power up

Connector CN123
Pin Number, Label, Voltage

Pin1 +5VSTB, +5.0V
Pin2 +3.3V, +3.3V
Pin3 GND 0V

etc.

[dick_barton]

Re: No audio no video no backlight on LG47LX9900

I should have said photo of the power supply and readings from the connectors also on the power supply.

[Ashish_Jamesh]

Re: No audio no video no backlight on LG47LX9900

Thanks for reply sir. I will upload high resolution pics as soon as possible.

[Ashish_Jamesh]

Re: No audio no video no backlight on LG47LX9900

1 question arise here..

If I unplugged the power strip from AVBoard tv doesn't power on.

So I read the voltage with tv on and I got 24.3 instead of 24v, and 3.4v instead of 3.5v, 12v pins give me perfect 12v output.

[Ashish_Jamesh]

Re: No audio no video no backlight on LG47LX9900

These are few pics of Board of PSU, T-Con, Main A/V, Master LED Driver, Slave LED Driver....

[dick_barton]

Re: No audio no video no backlight on LG47LX9900

Hello Ashish,
You have to help us help you. The picture of the power supply board is to small to work out what the voltages on the connectors should be.

You need to power up the set and give the voltage reading when in standby and when switching out of standby so that people here have an idea of what may be wrong.

I have attached a similar power supply picture and you need to give the voltages at the pins shown in the red boxes and list them as requested in post #5

Photo courtsey of Shopjimmy

[vinceroger69]

Re: No audio no video no backlight on LG47LX9900

I would also try to get a replacement LVDS cable as you have had to modify the contact ends this maybe causing issues so to rule it out change it if you can.

[dick_barton]

Re: No audio no video no backlight on LG47LX9900

I would also try to get a replacement LVDS cable as you have had to modify the contact ends this maybe causing issues so to rule it out change it if you can.

+1 Agree with you here.

[Ashish_Jamesh]

Re: No audio no video no backlight on LG47LX9900

I would also try to get a replacement LVDS cable as you have had to modify the contact ends this maybe causing issues so to rule it out change it if you can.

I bought another used good condition cable from local market but still no progress

[Ashish_Jamesh]

Re: No audio no video no backlight on LG47LX9900

Hello Ashish,
You have to help us help you. The picture of the power supply board is to small to work out what the voltages on the connectors should be.

You need to power up the set and give the voltage reading when in standby and when switching out of standby so that people here have an idea of what may be wrong.

I have attached a similar power supply picture and you need to give the voltages at the pins shown in the red boxes and list them as requested in post #5

Photo courtsey of Shopjimmy

I agree with you sir..as per all red box where they say 24V I got 24.3, and where they say 3.5V I got 3.4V, and where they say 12V I got perfect 12V. I measured this value with power on the TV. Now I will try to read the output again on standby mode. But i have one query that how can i read voltage from all 24pins? Because If I unplugged the connector TV not start.

[vinceroger69]

Re: No audio no video no backlight on LG47LX9900

where each wire goes in to the connector, if you push your red multimeter probe down the side of each wire it will touch the metal connector on the end of each wire so you can take a reading that way with the connector still in place .

[ReeceyBurger123]

Re: No audio no video no backlight on LG47LX9900

Quite sure the 12v runs all the time here and the Mb switches the 3.4 pv for the Led driver. Possibly Mb issue.

[dick_barton]

Re: No audio no video no backlight on LG47LX9900

I agree with you sir..as per all red box where they say 24V I got 24.3, and where they say 3.5V I got 3.4V, and where they say 12V I got perfect 12V. I measured this value with power on the TV. Now I will try to read the output again on standby mode. But i have one query that how can i read voltage from all 24pins? Because If I unplugged the connector TV not start.

First if I look at the power supply circuit I posted above it says
Connector P304
Pin1 = Err
Pin 2 = NC
Pin 3 = I-C
Pin 4 = PDM
Pin 5, 6, 7, 8, 9 = GND
PIn 10, 11, 12, 13, 14 = 24V

So where are the readings for Pin1, 3 & 4 just as an example.

If the only way to read the voltages on the connector is to turn the board upside down carefully then that's one way. Or you may be able to use a thin piece of wire pushed into the connector alongside the existing wire.

[budm]

Re: No audio no video no backlight on LG47LX9900

The power supply is OK otherwise you will not get the switched 12V and the switched 24V.

[dick_barton]

Re: No audio no video no backlight on LG47LX9900

Fair point Budm. One that I've overlooked.

[Ashish_Jamesh]

Re: No audio no video no backlight on LG47LX9900

First if I look at the power supply circuit I posted above it says
Connector P304
Pin1 = Err
Pin 2 = NC
Pin 3 = I-C
Pin 4 = PDM
Pin 5, 6, 7, 8, 9 = GND
PIn 10, 11, 12, 13, 14 = 24V

So where are the readings for Pin1, 3 & 4 just as an example.

If the only way to read the voltages on the connector is to turn the board upside down carefully then that's one way. Or you may be able to use a thin piece of wire pushed into the connector alongside the existing wire.

Sir whats the functionality of Pin 1=Error, 2=NC, 3=I-C, 4=PDM?

As per my reading with tv standby mode I got only 3.4v, 24v & 12v line shows 0v.

And after switched on the tv I got 3.4v, 24.3, and 12v.