LG 47LE5500 dark screen possible no sond

[topcat150]

first let me say thanks to all those who help out us novices. Your advise and help is greatly appreciated.

I was recently given a 47LE5500 which in an LG LED Backlit tv. Owner thought the set had just died one day when they went to turn it on. Dont know if there was sound or not. I tried hooking up a sound source to an av input but since screen is dark i cannot see any menus. I fumbled through the remote but never got sound. when powering up with the remote or main power button the Power light comes on and stays a steady white color. No flashes. also the LG logo lights up. I open up the set and found that is uses the EAY60803301 power board. It has a daughter board that is labeled LED driver. I found 4 fuses that all are good. I measured the voltages on P201 and have 12, 20, 3.5 supplies. the power on lead is at 3.4V.
I cant figure out where to measure the Vled voltage but board says it should be 136v typical.
I know all these sets have a power up sequence so i dont know if i am in some sort of standby mode or not. both the Main board and the power board look fine with no indication of overheating

I am a techy so i can use meters and scopes to make measurements.
Any help or advice to get this guy up and working is much appreciated.
thanks
Tom C (aka topcat150)

[ReeceyBurger123]

Re: LG 47LE5500 dark screen possible no sond

Check this out:

https://m.youtube.com/watch?v=Bf5T2wwtydY

You might be asked to change your name as well other Topcat is the owner of BCN

[budm]

Re: LG 47LE5500 dark screen possible no sond

Please up load good clear pictures of the whole back side of the TV so we can see how all the boards are connected together, then the pictures of each board.

[topcat150]

Re: LG 47LE5500 dark screen possible no sond

Ok, just got back working on the set. this is m first time trying to attach pictures so hopefully you will be able to see everything
First picture shows back of set opened up. there are only two boards that are visible. the power board and the main board. there are 3 connections at the top left edge. One takes power and signals to the main board. the very top left connector marked p 204 has wiring that goes directly into a slot at top of tv which i would guess feeds led matrix. This connector is in direct alignment to the LED driver board which is a motherlike board on the power board. I do have voltages on these 12 pins as follows
(I cant tell if first pin id is a letter or number but i think it is a 0)
From top to bottom:
02-1A 126V
nc
02-1C 21.9V
02-2C 20.6V
02-3C 21.9V
nc
nc
01-3C 21.75V
01-2C 21.9V
01-1C 21.2V
nc
01A 126V

Next is connector P205 which also goes to back of set and is also aligned with the led driver board.
voltages as follows
from top to bottom
04-A 126V
NC
04-1C 21.8V
04-2C 22V
04-3C 21.8V
NC
NC
NC
03-3C 22.6V
03-2C 21V
03-1C 22V
NC
03-A 126V

so it appears that the led driver board is putting out drive voltages, just don't know what they should be.
also when powering up the set there is no flash of light on the screen
next picture should be the power board and then the close up of the LED driver board, then the main board.
thanks
tom

[topcat150]

Re: LG 47LE5500 dark screen possible no sond

that should be the top right of the power board.

[topcat150]

Re: LG 47LE5500 dark screen possible no sound -Updates

here are a couple more readings on the Power board

Drive On = .04 volts (I don't know if this is supposed to be High or low when active. I tried tying it to the 3.3 v supply vdd, through 620 ohm pullup resistor and the Drive on pin read .6 volts when tied to vdd.

with the set off i took a resistance measurement on the DriveOn Pin. With the cable on and connected to the main board i got about 1.7K ohms. with the cable disconnected i got about 47K ohms. Just FYI

the PD1m1 signal is at 2.95 volts. (not sure what this pin does)

as mentioned earlier the Power ON signal is at 3.4V.

If anyone can help me with these signal levels and which are inputs to the power board from the main board and vice versa that would be much appreciated
Thanks again

[thoma]

Re: LG 47LE5500 dark screen possible no sond

see also:https://www.badcaps.net/forum/s...amp;page=3
regards thoma!

[lalexan]

Re: LG 47LE5500 dark screen possible no sond

I fixed my LG 47LE5500 today. It froze during normal operation, restarted and gave a black screen, no flashing, no back light, no sound, not detectable by a PC. It could turn on and off, LG logo would turn on, on-screen control and the remote seemed to work, but that's it.
Basically the symptoms are almost identical to the ones described above, well 2 years ago. I've got similar power supplies and LED driver readings (maybe slightly lower - 18V instead of 21V on LED driver).
The way it died (with reboot) made me suspect the main board - EBU60904703, getting solder ball cracks in CPU BGA. I removed the heat sink and did a re-flow with a preheat, some flux around the BGA, and a heat gun to ~210C. Read this post for more details: https://www.badcaps.net/forum/showpo...&postcount=107
The thread is very old, so I'm posting mainly for completeness.
Best of luck!

[Nick's Tvs]

Re: LG 47LE5500 dark screen possible no sond

The entire LE and LX series are infamous for bad main boards with cracked solder joints on the BGA chip. They can cause either no hdmi ports to work properly or tv turns on and off button and remote work, but you won't ever get any picture, no back-light, or sound from the set. I don't think I ever have seen one of these TVs with any other issue than bad main board.