LG 55LV5500-UA no picture or sound

[budm]

Re: LG 55LV5500-UA no picture or sound

Hey guys I have the same LG (55LV5500-UA) with a slightly different issue. What happens is when the tv is plugged in only the light for the power wil be on and when you turn the tv on the light changes but no back light at all. I poped the back of the tv open measured the power to back light seems good what I have found though no power whatsoever at the fuse on the T-con Board. I have checked the connector from power supply to mother board all voltages and grounds are there. Any thoughts would be appreciated. I suspect the main board but want to see if anyone got anything similar before throwing 80+$ into a board or posibly just fix it myself

So you do have backlights, right?
The DCV to the T-CON comes from the switched MOSFET that is turned on when TV is turned on, so the main board will have to be looked at and locate that switched MOSFET.
You must up load good clear pictures of YOUR boards and the whole back side of the TV. It may be even better to start a new thread with make, model, picures, and all the details.

[ivpavel]

Re: LG 55LV5500-UA no picture or sound

No backlight at all but the voltage from the power supply to the leds is there. I will upload the pictures tonight when I get home from work. Do you know which MOSFET (label number on the board) is the one that send voltage to t-con? I belive someone in the earlier replies posted a schematics of the tv.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

A buddy of mine just dropped one of these sets off to me. I'll see whats up in the morning.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

Finally, I am back to this tv.
Tv power led switches from red to white with no video or sound, no backlights.

In checking output voltages of power supply, connector p201, no 24v on power-on pin (bottom pin). It reads 3.4v.

There is the 24 on the pin right above it as also indicated by the key above.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

finally, i am back to this tv.
Tv power led switches from red to white with no video or sound, no backlights.

In checking output voltages of power supply, connector p201, no 24v on power-on pin (bottom pin). It reads 3.4v.

There is the 24 on the pin right above it as also indicated by the key above.

ignore. I misread the pinout info on the board.

[syaoran123]

Re: LG 55LV5500-UA no picture or sound

So r u getting 24V or not? What about the other voltages?

[budm]

Re: LG 55LV5500-UA no picture or sound

skip.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

Yes the 24 volts is okay. The other voltages are okay as well however for some reason the TV still is not turning on. I tried to follow the troubleshooting guide in the service manual that I found on the internet. After getting about more than half of the way through I could not find the remaining components that it asks you to check. If there are any other checks to be made or any tricks I can try let me know.

[budm]

Re: LG 55LV5500-UA no picture or sound

Can I get the DCV readout of all the pins for that connector?
Please make sure to put down the pin name and follow by the DCV reading when the TV is OFF and when the power switch is activated?

https://www.badcaps.net/forum/attach...1&d=1490026373
You have 24 pins total, you can skip the GND pins, it is also setup as odd and even pin rows so make sure you are reporting the right pins.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

All of these voltages are from in the "On" state.
You'll also notice that the pinout from the board in inverse of that which the drawing shows.

Pin 1
3.43
24.73
24.73
24.73
0
0
0
0
3.53
3.53
3.53
3.53
0
0
0
0
12.05
.038
12.05
0
12.05
3.175
0
0

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

Hey Bud,

After I posted those voltage readings, I found a thread that you helped a guy on with a similar problem. I found the info from an LG training manual there and more info than I needed to come to my conclusion. I think it's going to be a main board replacement that fixes this. I priced one last week at 130. I was hoping to give this one last shot to surprise the owner but... no longer worth my time.
I advised the owner that the board cost 130 and I couldn't guarantee that this same issue cant pop back up a year or two from now.

This TV is about 5 years old. A 55 inch that was about $1000. TV's should last longer than that. In my opinion these companies like LG do not care about making a product that lasts.

[syaoran123]

Re: LG 55LV5500-UA no picture or sound

Your problem is the mainboard. Search on how to reflow the processor. The processor is located under the large heatsink.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

Thanks for the info. I just did a keyword search here for "LG REFLOW" and I was shocked how many pages of threads there were.

I may give this another try. Its definitely worth it. I need to get a heat gun.

[syaoran123]

Re: LG 55LV5500-UA no picture or sound

good luck and remember to post the results

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

I tried the oven reflow method. No difference. I may try again later but i'm skeptical of this process due to everyone's oven is different. I hope my oven regulates temp enough to melt the solder evenly. I really dont have anything to lose at this point.

[heavymachines]

Re: LG 55LV5500-UA no picture or sound

Best to use heat gun or reflow station..... Oven works ok on laptop boards, but boards with electrolytics not so much.





However i went back and looked, all i could see was solid caps, might be ok... Oven is risky, i have had 100% success rate on those crappy hp dv series mobos however destroyed few other boards experimenting reflow graphics cards and whatnot., I found making a jig on a hotplate and reflow station and a good thermal profile with a k type thermal probe. Proper sinking or shims after the repairs last quite a few years some 4 yrs and counting still working to this day and works good on xbox 360s and ps3's, Haven't had the need to reflow TV's yet..... Knock on wood.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

Something just will not let me give up on this TV yet. I followed the jumper instructions on how to get the backlights to turn on. They and thier voltages are correct. They stay on as long as I have the set on.

Now... I just using that as a starting point. The circuit never fires up the backlights. If the test has me jumper 3.5 volts to the pin 18.... then pin 18 (as shown in this drawing) should have about that 3.5 voltage for a normal running situation. This drawing taken from the training manual shows 3.28 volts should be present there on pin 18.
My board only shows .034 on pin 18 when hooked up regular ( not jumpered). Please take a look at my notes on the drawing for that circuit. They dont seem right at all but where do I look next? I would assume taht IC602 is putting out the right voltage on that pin 10 (3.5) and then is Q504 isnt doing it's job? One thing that I didnt check is for the emmitter to be properly grounded as shown in the drawing. I dont know if that would cause it to be in the state that it is or not. My transistor theory is kinda rusty at this point.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

Well... I just sold this one today - non working. $100

It didnt cost me anything to acquire it. The customer gave it up once we learned of the mainboard cost with a possibility of this happening again. I told him not to buy LG again. It needed that damn hard to get main board. I saw one on ebay for $130.

[dick_barton]

Re: LG 55LV5500-UA no picture or sound

If Pin 18 should be at 3.5v then the transistor Q504 needs to be switched off. So pin 10 should be at 0V. It looks like the INV_CTL signal is holding INV_ON in the off state.

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

I saw about five threads where they had the same exact problem and neither of them could find an answer to why that pin 10 stays high. Its all good though. I got my money out of it.