LG 47LD500-UA not turning on

[salongaopm]

I have an LG 47LD500-UA lcd tv that is not turning on, no light on standby led, no sounds or picture.

Below are what I have done so far:

1. checked the voltage to +5v pins that leads to main board - I noted that it will read at around 5.+v immediately after the tv is plugged in to an outlet and will gradually goes down up to 0 after several minutes.
2. After watching a few YouTube videos and reading several post online, I replaced 3 parts that I thought was defective....did not solve the problem.
3. I checked the small fuses (3) from the main board for continuity and they seem to be okay.

Any help will be greatly appreciated. DISCLAIMER: I don't have any electronics educational background and not really sure how to use multimeter properly. So please take that in consideration when giving instructions on what to do. I have a descent soldering station (CSI Station 2A) that I can use to solder some electronic parts.

Attached are pictures of main board, power supply and the multimeter (I got it free) that I am using.

[salongaopm]

Re: LG 47LD500-UA not turning on

more pictures

[salongaopm]

Re: LG 47LD500-UA not turning on

bump

[Bill79]

Re: LG 47LD500-UA not turning on

Looks like you had the same issue that I have.
Your post was a long time ago and atleast here no one helped you.
Did you learn anything to get you're problem resolved?
From the looks of your pics, we have the same TV. Mine is apart, going to check that fuse next.

[heavymachines]

Re: LG 47LD500-UA not turning on

Take straight clear focused pictures of entire back of tv and individual boards . Tell us tests you have done so far and descriptive symptoms... You'll get better results.

[Bill79]

Re: LG 47LD500-UA not turning on

Take straight clear focused pictures of entire back of tv and individual boards . Tell us tests you have done so far and descriptive symptoms... You'll get better results.

Good Day, Thanks for a response.
Well, as far as pictures are concerned, I have a problem uploading pictures from phone to PC).
But my boards look absolutely no different from the topic posters picture for his TV.
His boards have the same (what I thought were) defects on them.
One thing I did find (that a camera would not have picked up) was on the back of the power board there was a piece of dust that might have gotten through the back panel, fell (inside the TV) in between the metal case the back of the power board on the (soldered through the board) terminals.
This speck was as fine as hairs and I saw them under close examination under a 4 tube fluorescent shop light.
These dust hairs were touching the terminal next to it and also 2 more terminals on the same (object that was soldered to the board) were grounded by a dust fiber.
On the other side of the board the object that is soldered in identifies itself as U101 on the front of the board.
I do not have that much solid state knowledge to know what some of the objects are and do on a solid state board.
These pieces of dust were scattered in a way that looked like they have been static charged toward both other terminals and even the metal back wall.
This U101 has a heat sink on it, so that tells me it gets hot and needs better cooling.
But, this was an observation after opening up the back and looking. I am not sure if this is the cause of my problems.
I have no wiring diagram either.
I know this board has issues with capacitors, but all those on the low and high voltage side look good (not puckered on top or no oozing).

But Sunday morning about 5 AM I was watching TV, my cable provider (Comcast) done their daily updates to their X1 platform.
Normally, the TV goes through power and video feed surges as it loads updates and restarts their gateway. Normally when done the TV will resume what I was watching/channel I was watching.
This time, there was no resumption. I also had no power (green) or red (standby) light.
At any time when plugging in the set did I hear (back off) any power engaging, no relay clicks no nothing when plugging in and un-plugging the power cord into the power board.
I do have a multi meter and the fuse checks good using continuity and resistance.

[dick_barton]

Re: LG 47LD500-UA not turning on

What DC voltage do you have on the bridge rectifier "+" & "-" pins. These look like the outer pins. Use you meter set to DC and connect the probes to the legs.

What AC voltage do you have when you measure to two inner legs "~". Again set meter to AC and carefully use your meter probes on the two inner legs.

[Bill79]

Re: LG 47LD500-UA not turning on

What DC voltage do you have on the bridge rectifier "+" & "-" pins. These look like the outer pins. Use you meter set to DC and connect the probes to the legs.

What AC voltage do you have when you measure to two inner legs "~". Again set meter to AC and carefully use your meter probes on the two inner legs.

Good Day, Thank you for your reply.
Okay. I have done what you advised.

I used alligator clip test leads on the DC (outer pins) and then to my meter like you advised.
I am getting between 156.9 and 157.0 VDC when board is plugged in and when you unplug it, the DC voltage slowly drops off to zero.

On the AC side (inner) I had to use just the leads on my meter and I got 122.6 volts.
AC side atleast sounds good to me.
What is the DC out put "supposed to" be? 157 volts sounds high.

[dick_barton]

Re: LG 47LD500-UA not turning on

The AC side is 122.6V but I thought the AC voltage was 115V for the USA which would give 1.414 * 115V = 162V DC at the bridge rectifier.

If it was 122.6V then it should come out as 173V?

What is the voltage written on the side of C809, and the other two large capacitors alongside it and what DC voltage do they read between the two legs of each of them.

There's also a fuse marked F102 alongside. With the power off and plug removed from the mains supply can you check that it has continuity using your meter on ohms.

[Davi.p]

Re: LG 47LD500-UA not turning on

The method to begin tests on a tv like this is always the same, you procured some high wattage resistors as a dummy load, for the 5v a pair of 3,3ohm 10W can go well, for the 3,3v the same 3,3ohm 10W is ok, for the 12-13v use a 12v lamp like the ones for rooms (halogen) or car lights. Then attach to the mains current only the psu with loads, for the standby voltages like the ones marked +5vsb you better put 2 3,3ohms in series, if the psu works ok you read the right voltage on outputs and after half a minute resistors goes hot.
The lamps will glow..

[Bill79]

Re: LG 47LD500-UA not turning on

The AC side is 122.6V but I thought the AC voltage was 115V for the USA which would give 1.414 * 115V = 162V DC at the bridge rectifier.

If it was 122.6V then it should come out as 173V?

What is the voltage written on the side of C809, and the other two large capacitors alongside it and what DC voltage do they read between the two legs of each of them.

There's also a fuse marked F102 alongside. With the power off and plug removed from the mains supply can you check that it has continuity using your meter on ohms.

Good Day,
I am assuming when you said "voltage on the side of C809 and the other tow large caps alongside", I assumed you meant C609.
NOTE in a new reply below I will post brand new close up pics of (my actual board) to help in referencing circuits.

Assuming you meant C609, all 3 are marked 450V and all three check in at 162.2/3VDC when tested with board plugged in and out of TV on a dielectric mat.
The fuse tests at 2-3 ohms, same reading as if I touched the two terminals together on my meter.

[Bill79]

Re: LG 47LD500-UA not turning on

I had removed and taken much better pictures of my actual board.
I had noticed after you wanted me to test C809 after looking and realizing there was no C809, I looked at the topic posters pics and his were a little blurry when it came to close ups.
So I will post better, detailed pics.
And again, this IS MY ACTUAL power board.

Hope this helps us in future relating to this circuitry.

[budm]

Re: LG 47LD500-UA not turning on

https://www.badcaps.net/forum/attach...5&d=1491077827
So to be clear, right now you do not have any DCV at all on any pin of that white connector, correct?

[budm]

Re: LG 47LD500-UA not turning on

BTW, your board is
Vizio/LG 0500-0412-1000 (PLHH-A945A) Power Supply / Backlight Inverter
Pictures provided by shojimmy.

[Davi.p]

Re: LG 47LD500-UA not turning on

from post #1:
"1. checked the voltage to +5v pins that leads to main board - I noted that it will read at around 5.+v immediately after the tv is plugged in to an outlet and will gradually goes down up to 0 after several minutes. "

this is maybe a mainboard fault, but without test the psu by itself who can say? I don't know why the need to test voltage on primary side..

[Bill79]

Re: LG 47LD500-UA not turning on

BTW, your board is
Vizio/LG 0500-0412-1000 (PLHH-A945A) Power Supply / Backlight Inverter
Pictures provided by shojimmy.

Yes Sir, that is the correct board.
I did see that on Jimmy's website, but I think they were out of stock on it to buy a new one.
But yes, that is the correct one.

[Bill79]

Re: LG 47LD500-UA not turning on

from post #1:
"1. checked the voltage to +5v pins that leads to main board - I noted that it will read at around 5.+v immediately after the tv is plugged in to an outlet and will gradually goes down up to 0 after several minutes. "

this is maybe a mainboard fault, but without test the psu by itself who can say? I don't know why the need to test voltage on primary side..

Yes, I am getting no voltage at the +5 pins at the out put to the main board.
Dick Barton and I went through some checks already.
I replied to him this morning with relevant information.

[Davi.p]

Re: LG 47LD500-UA not turning on

But the O.P. don't says "no 5v"... please be clear when you tag along another one's post, if your case was different it was better to open a new thread, if not threads reaches orribile post numbers like here in this forum happens.. who has wish to read 133 post to come to the point?

[budm]

Re: LG 47LD500-UA not turning on

OK, so to be sure, if you run the power supply board by itself without having main board connected to it, you do not get any 5vdc, correct?

[budm]

Re: LG 47LD500-UA not turning on

Check the White rectangular fuse F102 (T4A H 250V).