52LG50 Has Mind of its own

[Lireb93]

Re: 52LG50 Has Mind of its own

0000 is the factory code and it worked

[Lireb93]

Re: 52LG50 Has Mind of its own

I replaced the Main Board in the set and everything seemed to be fine. Was just like getting a new TV. However, this morning I went to turn it on, and when I hit the remote the TV clicked twice and came on and went off and then came on. What is the problem here? I replaced the the IR sensor(switch), main board, so what else could be causing this? I unplugged and did a factory reset by holding in the on/off switch for about a minute and the sensor light glowed. It is still unplugged and will be for a couple hours before I try it again. Any ideas?????????????//

[Lireb93]

Re: 52LG50 Has Mind of its own

Replaced the Main Board and all was well for a couple days, and then it started on/off ect. Today it comes on and you can't shut it off. Turn it off and it comes back on. Could it be the power cord? It is a little wobbly when installed and it is the right angle plug and not the on that is straight in line with the cord.

[chicago77]

Re: 52LG50 Has Mind of its own

Well I have the same problem and I've read that most people have replaced different boards and it reall has only fixed the issue for a few weeks.

I have figured out that if I disconnect any one of the 4 connections to the LCD the power stays on or off. So my thought is that something is not able to draw enough power to run all four. Maybe an electrolytic cap is starting to fail and needs to warm up before functioning. I don't have any obvious ones but if they are crapy caps they might be performing just below spec.

[chicago77]

Re: 52LG50 Has Mind of its own

Also does anyone know what the board at the top center of the TV does? I can't get the cover off it currently.

[fierygt]

Re: 52LG50 Has Mind of its own

That is the timing control (t-con) board. It delivers the image to the lcd screen.

I have this same TV, with this same problem, and can't figure it out. I replaced all the capacitors in the power supply, even the smallest ones, and it made no difference. The original ones didn't even look bad, but I did it anyway. If I unplug the two connections from the PSU to the inverter boards, it will act 'normal', and stay on and turn off like normal, but obviously there is no picture. Another person said it might be in the mainboard, but that doesn't seem right, if when the inverter connections are disconnected, it will power on and off like normal. There are a few capacitors on the inverters themselves, but I have taken off one side's shielding, and they look ok. I have also disconnected the front panel, as part of my process of elimination. I guess I am curious if there is a way to test the inverters or has anybody replaced them with success?

[gfox]

Re: 52LG50 Has Mind of its own

Did any of the people who posted on this thread ever figure out what was causing their 52LG50 sets to cycle power, or not go off and stay off?
I have the same television doing the same thing.
Thanks!

[fierygt]

Re: 52LG50 Has Mind of its own

There is a 5w 6.8 ohm white ceramic resistor, next to the black relay, near where the 120v line runs into the power supply. Mine is reading around 10 ohms, which assuming it has a 5% tolerance (it doesn't really say on it), would make it well out of spec. I have not yet replaced it, and still need to get one ordered to find out, but that is where I am putting my money at the moment.

[gfox]

Re: 52LG50 Has Mind of its own

Fierygt,
Do you also have a 52LG50 that is doing the same thing?
If so, I was wondering if you could do me a favor and try something with yours? The one thing I have noticed is that the television works just fine as long as the back cover is not on. I have removed the cover and replaced it without screws multiple times to watch the problem come and go. To further understand where the plastic cover is effecting the operation I placed the cover just over certain modules on the back of the television. I found that the when the cover is within 6 inches of the Power Supply the problem exist. So at this point to me it seems like there is some EMI or noise issue that causing interference when the cover is within proximity (does not have to be touching).
I tried measuring the resistance of the plastic cover thinking maybe it is made out of some conductive plastic, but found nothing.
If you could try operating yours with the back cover off I would be interested to see if have the same findings.

[fierygt]

Re: 52LG50 Has Mind of its own

I have the back cover off mine, right now, and I tried it without it, but it cycles on and off and makes no difference for me.

[gfox]

Re: 52LG50 Has Mind of its own

WOW! Never mind I could make it come and go 30+ times by removing and replacing the cover the night before last and then last night it was giving me the problem even with the cover off.
The 5w 6.8 ohm white ceramic power resistor that you referred to is measuring 7 ohms on mine in the circuit.
The thermistor (which resembles a ceramic cap, labeled TH) next to the relay measures about 10 ohms.

[Agent24]

Re: 52LG50 Has Mind of its own

If I unplug the two connections from the PSU to the inverter boards, it will act 'normal', and stay on and turn off like normal, but obviously there is no picture.

PSU capacitors on the way out, extra power draw from the inverters causes PSU overload and shutdown?

[fierygt]

Re: 52LG50 Has Mind of its own

"I replaced all the capacitors in the power supply, even the smallest ones, and it made no difference."

I ordered a complete kit of new capacitors for the PSU, even though none of mine looked physically bad, and replaced every electrolytic capacitor on there, besides the two largest ones, and it didn't fix the problem. I've researched the issue in other forums, and others have said they replaced the capacitors too, and it didn't fix this particular problem with this particular tv. Which is why I started looking in other places. I haven't yet ordered the 6.8 ohm resistor replacement to test, just because of priorities, but maybe someone more intelligent than me, can give a defacto answer as to how 'out of spec' that 6.8 ohm ceramic resistor can be. To me, if it's not within a 5% tolerance, that seems bad. It does seem like "something" is drawing extra power, but it must be something besides the PSU electrolytic caps.

[Agent24]

Re: 52LG50 Has Mind of its own

Sorry, guess I didn't read everything! It does sound like you're right about that resistor.
Even if it had a huge 20% tolerance (which I doubt) it could only be 8.16 Ohms at the highest and still be in spec. Hopefully it is the cause of the problem.

[gfox]

Re: 52LG50 Has Mind of its own

As cheap as the power resistor is it wouldn't be a bad thing to replace it, but I highly doubt that is the problem. Especially since mine measures very close to spec and still has the same issue as yours. I would have to believe the root cause of both of ours will be the same.
As I mentioned earlier I did change out both of the larger 220 uF caps, because one of mine was bulged on the top, but it did not help the problem at all.
The night before last I took the power supply out again and started looking to see what is driving the small relay on the PS. All I did was take it off and check a few of the diodes around the relay and then put it back. The television turned on and then shut right back off. Now I can't even get the television to turn on at all. I haven't had a chance to really look into it, but my thought is that there is something wrong with the relay itself. I will be checking to see if I am even getting voltage to the relay coil. If there is, I will be taking it off of the board and applying 5 volts to the coil to see if it is still operating properly.
I have been an Electrical Engineer for 17 years, (which doesn't make me a television repairman, LOL) and this one has me stumped.
I have been refusing to just start swapping out modules, especially since so many people have posted on many sites that they have taken this route and the television only works for a short while, then start acting up again.

[gfox]

Re: 52LG50 Has Mind of its own

Fierygt,
I told you that all of a sudden I completely lost power and that my television wouldn't even try to power up. Well, I found the problem I why it won't power up. I lost that power resistor that we have been talking about. I couldn't believe it! Either that is very ironic or that has been a weak link. I never did anything that should have effected that resistor and it has just completely opened up.
I will let you know how things go once I replace it.
Have you replaced yours, yet?

[budm]

Re: 52LG50 Has Mind of its own

Is this the power supply board you are working on? The OP never provides me the pictures I requested.
http://www.shopjimmy.com/lg-eay41752...wer-supply.htm

[fierygt]

Re: 52LG50 Has Mind of its own

Is this the power supply board you are working on? The OP never provides me the pictures I requested.
http://www.shopjimmy.com/lg-eay41752...wer-supply.htm

budm, Yes, that is the power supply I am working on.

gfox, I haven't even gotten around to ordered it yet, just because of priorities, but I was planning to soon.

[gfox]

Re: 52LG50 Has Mind of its own

fierygt
I just ordered 5 of them, so if it fixes my problem I will let you know. I could stick one in the mail for you also. They were only less than $0.20.

[fierygt]

Re: 52LG50 Has Mind of its own

gfox, for sure.