LG 55LV5500-TA No picture, No sound

[vk5bd]

Hello all,

What a useful site, so much information and knowledgeable people, it is great, wish I had found it earlier.

So I have a LG 55LV5500-TA with no picture or sound as I have seen in a few other threads for similar model TV's. I have followed the training manual posted here for a similar model and have proven the power supply is okay, and that the LEDS can be turned on by jumpering the power supply connector. What I have found is there are no volts on the fuse on the T-CON board, I pulled the main board out of the TV and tested the components that should feed 12v to the T-CON board and all the components test okay, it is as if the main control is not turning on this supply. Another observation that may or may not help is the LED in the bezel of the TV, when your power the TV with the remote, this LED starts off red, then goes white, goes off, then becomes white and stays on.

[dick_barton]

Re: LG 55LV5500-TA No picture, No sound

A good place to start is to provide the voltages as written in the yellow box as found on the 24 pin connector in the red box.

[vk5bd]

Re: LG 55LV5500-TA No picture, No sound

Hello Dick,

With the TV turned off, the only voltage present is the 3.5V which measures 3.551 with respect to chassis.

With the TV turned on I got the following:

Pin..........Label..........Voltage
1.........POWER-ON......3.437
2->4........24V..........24.73
3->8........GND...........0.003
9->12......3.5V...........3.541
13->15....GND...........0
16.......VSYNC-IN.......0
17,19,21...12V.........12.09
18.........DRV-ON........0.036
20,23........NC............0
22...........PWM..........3.186
24.........ERROR.........0

Thanks for you quick response,

Regards,
Bevan

[dick_barton]

Re: LG 55LV5500-TA No picture, No sound

The voltages look good. I'm not sure what Vsync-In does but I am a little suspicious that DRV-ON is low.

Have a read through the following thread.
https://www.badcaps.net/forum/showth...light=55LV5500

This has a blown Q507 device which should supply the voltage to the Tcon.

Edit
There is a schematic for the set at the above link. It looks like DRV-ON is the Inverter control input.

[budm]

Re: LG 55LV5500-TA No picture, No sound

Can we see the pictures of the whole backside of the TV so we can see how all the boards are connected together?

[vk5bd]

Re: LG 55LV5500-TA No picture, No sound

Here is the layout of the boards of the TV, looks fairly common to other models in other threads.


From the training manual for a 55LW5600 (not my model but seemed very similar) I was able to test the DRV-ON signal, when I applied the 3.5V supply to the DRV-ON connection, the TV's backlight came on.


Have checked Q507 and believe it is working, I took the main board out of the TV and tested it on the bench, I applied 12V to L511 and put a short across Collector to Emitter of Q506 and was able to see volts appear at PANEL_VCC. While I had 12V connected to the board, I could measure 1.9v at PANEL_CTL which was enough to turn on Q505 which turns off Q506. I believe that volts on PANEL_CTL means NO volts to PANEL_VCC based on the inverting logic of Q505 and Q506.

[budm]

Re: LG 55LV5500-TA No picture, No sound

Here is the layout of the boards of the TV, looks fairly common to other models in other threads.


From the training manual for a 55LW5600 (not my model but seemed very similar) I was able to test the DRV-ON signal, when I applied the 3.5V supply to the DRV-ON connection, the TV's backlight came on.


Have checked Q507 and believe it is working, I took the main board out of the TV and tested it on the bench, I applied 12V to L511 and put a short across Collector to Emitter of Q506 and was able to see volts appear at PANEL_VCC. While I had 12V connected to the board, I could measure 1.9v at PANEL_CTL which was enough to turn on Q505 which turns off Q506. I believe that volts on PANEL_CTL means NO volts to PANEL_VCC based on the inverting logic of Q505 and Q506.

PNL_CTL is active low, the PANEL_VCC is the Voltage for running the T-CON board, that PNL_CTL should go the mirco controller pin.

[vk5bd]

Re: LG 55LV5500-TA No picture, No sound

I agree, PANEL_CTL needs to be taken low for the 12V to be allowed to go to the T-CON board, so I am thinking the processor is not commanding the output, either due to detecting a fault or is faulty itself, this would also explain why no sound, the processor is not working at all or has decided there is a fault condition, The flash of Red then White of the Bezel LED a clue as to a fault code?

[Iyee]

Re: LG 55LV5500-TA No picture, No sound

Just as others have done. I removed the main board and heatsink and used a little flux around the drive ice and the two PCs of memory I think. These three chips are all bag, ball solder.
Link to video of reflowing thebthree chips. A li%let liquid flux then heat with hot air then allow to cool don't move while heating or parts could be misaligned.

https://drive.google.com/file/d/1tyh...w?usp=drivesdk

[eriklhayes]

Re: LG 55LV5500-TA No picture, No sound

It looks like the google drive file has been removed. I have the same problem and want to reflow the chips. Can you provide instruction on how to remove the heat sink?
Thanks,
Erik

[eriklhayes]

Re: LG 55LV5500-TA No picture, No sound

There are these Q505, 506, 507 kits for the main board for sale on ebay. Any luck trying these?

[tvtimmy]

Re: LG 55LV5500-TA No picture, No sound

There are 4 spring loaded pins on the big black heatsink that have to be removed. Pinch the ends from the backside and push through. Take off the rubber pad from the icu and use a heat gun on LOW for about 45 seconds. Make sure you heat the entire area. Let cool then put back in and try it. I have two that have been working for 3 years now.

[eriklhayes]

Re: LG 55LV5500-TA No picture, No sound

That did it! THANKS. Sweat equity pays off again!

[viewfindr]

Re: LG 55LV5500-TA No picture, No sound

Thanks for all the suggestions above! I reflowed my unit today with a heatgun for about 45s, and it worked wonderfully after putting it back together. However, about 2 hours of operation later, the screen suddenly turned black, and I got the flashing power LED conundrum again, with no backlight, putting me right where I started.

Just tried reflowing for a second time with more heat, for 1min, but no go

Is the board just totally fried now and I'm out of luck?

[neilc6]

Re: LG 55LV5500-TA No picture, No sound

I have had zero luck baking boards with failed bga connections. Tried both a PS3 and a HP laptop. Both worked for a couple of months before problems came back. If it was my TV, I would have gotten the board reballed since a 55 inch LED still has value. Used boards will be expensive because of high demand or may fail in the future.

[viewfindr]

Re: LG 55LV5500-TA No picture, No sound

Thanks for all the suggestions above! I reflowed my unit today with a heatgun for about 45s, and it worked wonderfully after putting it back together. However, about 2 hours of operation later, the screen suddenly turned black, and I got the flashing power LED conundrum again, with no backlight, putting me right where I started.

Just tried reflowing for a second time with more heat, for 1min, but no go

Is the board just totally fried now and I'm out of luck?

Update: I stuck it in the oven per all of the descriptions online, and it seems like it's back to life for now. I wonder if it's because some other component needed to be reflowed, aside from the ICs under the heatsink.

[shelby5041]

Re: LG 55LV5500-TA No picture, No sound

hi
it seems there are 2 "fixes" for no video no backlight on this model tv..with all voltages from ps good....reflow main board or replace main board Q505 Q506 Q507

does anyone know which one fixes this issue? it cant be both.

thanks

[shelby5041]

Re: LG 55LV5500-TA No picture, No sound

well to follow up my question..i decided to try and heat the cpu looking chip and the 2 other chips near it and now the tv powers on fine..not sure its "fixed" but it wasnt powering on proper and now it is so we will see

it did seem to be a pretty common issue on this model tv so i figured go with the odds

i got tv for free so ..