LG 42LV5500 LED Edge lit...no picture,sound or backlights

[allsmith]

Hey fellas,i was wondering if any of you had a minute to give me some pointers on this tv i got out of the landfill?

The power indicator comes on and is red when unit is plugged into mains power, hit the power button and i hear a relay click and the indicator light goes to blue..

Backlights do not come on, and i have confirmed with a flashlight that there is no picture or sound with a dvd player hooked up.

I only get about 10VDC that slowly climbs up to about 40VDC after many minutes on the large filter caps when unit is in standby. I get 395 VDC on the large filter caps when the unit is turned on.

I have check the voltages on the connector from the psu to the main board and my findings are here...

TV turned ON

Error = 0v
PWM 12v = 11.8v
NC 12v = 11.8v
DRV-ON 12v = 11.8v
Vsync = 0v
Gnd = 0v
3.5v = 3.5v
3.5v = 3.5v
Gnd = 0v
Gnd = 0v
24v = 24v
24v POWER ON = 3.4

Tv turned off and in stand by

error = 0v
PWM 12v = 0v
NC 12v = 0v
DRV-ON 12v = 0v
Vsync = 0v
Gnd = 0v
3.5v = 3.5v
3.5v = 3.5v
Gnd = 0v
Gnd = 0v
24v = 0v
24v = 0v

The other connector voltages here...

TV turned on

Reverse = 0v
N.C = 0v
SCLK = 0v
Gnd = 0v
SIN = 0v
SCL = 3.2
SDA = 3.2
Vsnyc = 0v

All 0v when tv is off and in standby


I recently fixed a backlit LED tv that had 2 bad led's in it so when i got this tv home i was thinking that might be the problem and didnt do any voltage testing and went right to work removing the LCD panel and checked all the led's individually with a battery and all tested fine and working so i put the tv back together and did the voltages tests..

Can anybody look at my voltages and tell whats going on?...Any help would be appreciated!

I have had the PSU out and inspected and tested the fuses,they are good.
Have not had the main board out yet but i dont see any fuses on the top of the board,but i will pull it and inspect closer.

Also if you need any better pics,please just let me know and i will..Thanks!

[allsmith]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

Friendly bump

[dick_barton]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

The voltage on the capacitor of 395V appears to be about right for out of standby.

TV turned on has me a little puzzled
Gnd = 0v
Gnd = 0v
24v = 24v
24v POWER ON = 3.4 ?????


Turned off
Gnd = 0v
Gnd = 0v
24v = 0v
24v = 0v
Turned off

Is the last 24V supply only reading 3.4V when out of standby and if so that's a problem.

[Andrew F. Ali]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

The voltage on the capacitor of 395V appears to be about right for out of standby.

TV turned on has me a little puzzled
Gnd = 0v
Gnd = 0v
24v = 24v
24v POWER ON = 3.4 ?????


Turned off
Gnd = 0v
Gnd = 0v
24v = 0v
24v = 0v
Turned off

Is the last 24V supply only reading 3.4V when out of standby and if so that's a problem.

You have a Main Bd problem.....If you don't have the tools to troubleshoot then look for a working replacement.......if you do have the tools then troubleshoot the BGA circuit.....Most likely the IC, due to cold solder joints, is loose on the board...

[allsmith]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

The voltage on the capacitor of 395V appears to be about right for out of standby.

TV turned on has me a little puzzled
Gnd = 0v
Gnd = 0v
24v = 24v
24v POWER ON = 3.4 ?????


Turned off
Gnd = 0v
Gnd = 0v
24v = 0v
24v = 0v
Turned off

Is the last 24V supply only reading 3.4V when out of standby and if so that's a problem.

Thanks for replying...yes im pretty sure all i was getting at the 24v POWER -ON pin was 3.4 volts.. tonight i heated up the bga chip and now the tv is working..you can read more in my reply to Andrew F. Ali

[allsmith]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

You have a Main Bd problem.....If you don't have the tools to troubleshoot then look for a working replacement.......if you do have the tools then troubleshoot the BGA circuit.....Most likely the IC, due to cold solder joints, is loose on the board...

Thanks for replying...i believe you are right,and i have seen a lot a talk about the cold solder on the bga chips here lately while doing research...No i don't have any reflow equipment and i dont see any main boards available anywhere online either..one in Israel for 250 bucks is all i seen!

But i have read about heating up the chip and or using a regular oven to reflow the bga connections,also read that is not a permanent fix.

So tonight i said what the hey and removed the heatsink off the bga chip and gently and slowly heated it with a heat gun watching the temp with a infared thermometer closely and brought it up to 200 degrees fahrenheit and now the tv is turning on and working perfectly.

I got a feeling this fix is not going to last,do you think the oven trick might last a while?..Should i even attempt it?...i want to use the tv in my bedroom and will be my main tv but i don't want to have to keep tearing it apart to heat up the chip.

Do you recommend anybody that can reball my board or should i just look around for anybody that does reballing?..i have no idea what that may cost,you have any idea?

[Andrew F. Ali]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

This may not be a permanent fix but you did do everything correctly with very little prompting. No I don't think baking would be a good idea. I have never done it as I was afraid other plastics might melt. Some members have done it with success but I am never lucky. I believe though that your TV WILL work a long while and give you many hours of bliss. I don't know anyone to reball this for you. Trust me you did a very good job....It WILL last....Cheers

[allsmith]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

This may not be a permanent fix but you did do everything correctly with very little prompting. No I don't think baking would be a good idea. I have never done it as I was afraid other plastics might melt. Some members have done it with success but I am never lucky. I believe though that your TV WILL work a long while and give you many hours of bliss. I don't know anyone to reball this for you. Trust me you did a very good job....It WILL last....Cheers

Thanks!..but i couldn't have done it with out you guiding me in the right direction!..I just mess around with these tv's when i find them and really don't know what the heck im doing..lol..But with help from fellas like you here on badcaps i have learned a lot in the last few yrs and have fixed about 10 tv's..Plus i spend a lot of time doing research online before i come here to ask questions..

I go to a garbage transfer station everyday and have been getting a lot of tv's out of there this summer,all free but most have busted panels, but i bring them home anyway and strip the boards and the lighting in case i can use the parts in the future..So far this summer i have got 3 that the panels were good and was able to fix them with the guidance from the fellas on here.

Since i have a pile of mainbords that i probably wont ever use i may experiment with baking them in the oven to see if anything melts or not,or to see what parts i may need to remove before the bake..But i must warn you im a terrible cook!! lol ...But yeah anyways thanks again!

[Andrew F. Ali]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

Thanks!..but i couldn't have done it with out you guiding me in the right direction!..I just mess around with these tv's when i find them and really don't know what the heck im doing..lol..But with help from fellas like you here on badcaps i have learned a lot in the last few yrs and have fixed about 10 tv's..Plus i spend a lot of time doing research online before i come here to ask questions..

I go to a garbage transfer station everyday and have been getting a lot of tv's out of there this summer,all free but most have busted panels, but i bring them home anyway and strip the boards and the lighting in case i can use the parts in the future..So far this summer i have got 3 that the panels were good and was able to fix them with the guidance from the fellas on here.

Since i have a pile of mainbords that i probably wont ever use i may experiment with baking them in the oven to see if anything melts or not,or to see what parts i may need to remove before the bake..But i must warn you im a terrible cook!! lol ...But yeah anyways thanks again!

Nice...

[kybergreg]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

Hi,
thanks to allsmith's posts I was able to fix the same issue on the same TV type. Removing heatsink, heating the chip a letting it cool down did the job!
The TV was already ready to go to the junk yard when I came across this thread. I wonder why didn't I come with this idea myself because some time ago I repaired this way several notebook graphics cards.

Anyway it made to register here to say thanks to all!

[tvtimmy]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

I use a Wagner paint stripper gun with a modified heat tube I made. Works great, did 5 LG tvs so far.

[bartstop]

Re: LG 42LV5500 LED Edge lit...no picture,sound or backlights

I know this is an old thread but I wanted to add that I did the same thing with my wife's hair dryer. According to my thermal gun I got it up to 210. I had the heat on high, the fan on low and used the turbo function. The TV is working perfectly now. But who knows for how long.