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Russell H.
Russell H., Service Tech
Category: TV
Satisfied Customers: 9525
Experience:  8+ years of professional experience
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I have a 50PA5500-UG. I changed the cap, but still have the

Customer Question

I have a 50PA5500-UG. I changed the cap, but still have the same problem. The TV will turn on for a few seconds. Everything looks great, but then it shuts off. If I leave it plugged in, it will not even turn on that much again. If I unplug it for a few hours and try again, it turns back on for a couple of seconds and then the screen goes black. But there is still a glow to the black screen, as if it is still on. What boards should I change?
Submitted: 1 year ago.
Category: TV
Expert:  Russell H. replied 12 months ago.

Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.

There's a heat-related problem, or perhaps just a problem with overload to the power supply so that it shuts down completely in protective mode, I think. This, esp. if there is no blink code nor flash code after it shuts down... most likely a severe short in a board (or two doubtfully.)

The best way to find out what board to eliminate from the TV and to replace, would be to

1. examine all boards, one by one, both sides, and see whether any capacitors are bulging, or leaking fluid, or otherwise obviously overheated or defective.

2. also examine all boards, one by one, both side, to see if there are any brown spots under components, or any signs of overheating or arcing. Or, any burnt-out components, period.

3. After that, to get a good service manual for this model of TV, which could save you a lot in money wasted on boards swapped in that turn out not to be defective after all. If you are open to that option, please let me know, and I will research a source or sources for such an LG service manual.

Let me know as to the three points listed above, please. Thanks.

Customer: replied 12 months ago.
Hi Russell,Thank you for your reply.First, I want to let you know that I am an electrical engineer and I design circuit boards for a living. Also, I have my own lab with pick and place equipment and inspection equipment. I have looked these boards over and do not see any problems with them. The TV has only been used for a maximum of 10 hours since I purchased it and it has been hanging in a temperature and humidity controlled room. I purchased 2 of these identical tvs and one still works. After doing my research, I found that there is a common capacitor that bulges and fails. In this tv, the capacitor looked totally fine, however, I still replaced it. The problem did not change. I have seen other people say they have this problem and one or two of them have the problem that I have... in that the cap didn't fix the problem. Unfortunately you don't see any more answers / help in those forums. I downloaded the only service manual that I could find and it doesn't help at all. I do see some lights on these boards, and I believe one is flashing. finding a key to this flashing code might help. I thought the manual that I downloaded would help me there... No luck. I measured the voltages on the power supply and they seem to be inline with what others have said on the other forums. I don't have those voltages with me at this time, but if it does become important, I can remeasure them for you. Some people say that I have to desolder some pretty large chips and replace them. I would much rather by a new board and replace that instead of dealing with chip replacing.
Expert:  Russell H. replied 12 months ago.

What board has a flashing light on it?

I'm sorry to say that if it was bought new, by opening it and replacing a capacitor, you have voided the warranty. It would have been fixed for free in that case, if it were still warranty covered.

What voltages were inline with what voltages that other people mentioned?

Customer: replied 12 months ago.
Hi Russell,The Tv no longer had a warranty because I have owned it for more than 1 year. I tried to get LG to fix the problem before I entertained this repair.Okay here are the details:On the EBR74185001 PCB
There is a green LED D101
It blinks the following code:
Short, Short, Long, ShortOn the PB23A EAX64696604 we have a RED led that is constantly on.The voltages are:M5V=5.2V
VA=55V
VS=205V
17V=17.34V
STBY=5.2VIf you are unable to help any further, then I would like to just cancel this and get my money back. Thank you!
Expert:  Russell H. replied 12 months ago.

Well, STBY being at the same level as M5V, means that as a signal STBY is 'active' or 'On'. Your TV *is* in Standby mode, then.

I have to look up the three other voltages you mention. To double-check: you are in the US and using a US-usage-intended TV, on a 120-V house current, rather than in Australia or UK or another country that uses higher voltages? correct me if I'm wrong in that assumption.

I also have to look up the blinking and the red LED signals and their significance (if any.)

Customer: replied 12 months ago.
I am in the USA. Using 110VAC.I think I know now what I have to do. My power supply is within spec. One of the other boards is bad. I basically have to replace the other boards one by one until we find it.
Expert:  Russell H. replied 12 months ago.

A crude way, without any other guidance, is to have all the boards unplugged. See if the P/S doesn't come on in STBY. See whether the symptoms of the possible short circuited board have been relieved. Turn Off, pull plug, plug in one board into its slot, turn On, check for STBY and other indicators. Etc... eventually finding that the addition of one board back into the TV, produced symptoms of short, STBY, etc.

That could save a lot in bad guesses as to bad boards.