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adamd-mod, Just Answer Moderator
Category: TV
Satisfied Customers: 9
Experience:  Just Answer Moderator
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I have a faulty LG 42" tv. The red power light alternates

Customer Question

I have a faulty LG 42" tv. The red power light alternates red / white every few seconds. The controllers or side button have no effect. LG42SL9500. I obtained a replacement main board and tried it but it made no difference. On line suggestions were to insert 3.5mm jack plug into socket on back a few times but this also had no effect.
A red light on the optical socket also glowed briefly at the same time as the red /white indicator glowed red.
Any suggestions?
Many thanks
colin Smith
Submitted: 2 years ago.
Category: TV
Expert:  Aric replied 2 years ago.
Hello and sorry you're having problems. I may be able to help, but I need to ask for more info.
1) Did the original issue occur after a storm or power outage?
2) Does the light blink back and forth as soon as the set is plugged in, or only after the power button is pressed?
Customer: replied 2 years ago.
1). No. The first time the problem occured it corrected itself but a few days later recurred and would not correct despite frequently trying, both with the original main board (the one with all the sockets in it) and a replacement obtained on the internet- not new- but exactly the same problem.
2) problem blinking occures after a few seconds of plugging in the mains and two or three seconds between red then white then red etc...
Expert:  Aric replied 2 years ago.
Thanks for the reply. There's only one other component in the set that can cause this problem and that is the Power Supply Board. Since the 5 volt line the mainboard runs off is generated by the power supply- and your light blinks soon as the set is plugged in, this indicates a power supply board problem. Do you have a meter to test the 5 volt line on the supply board?
Expert:  Aric replied 2 years ago.
Do you need further assistance with this?
Customer: replied 2 years ago.

I do have a volt meter, but need to be sure to identify the power supply board. Do I follow the lead from the 240v socket, and presumably need to have the power lead connected. I have provisionally replaced the whole back panel and will have to remove this again which I am not able to do at this moment, but can try later.

Expert:  Aric replied 2 years ago.
Yes the power board is what connects to the Mains lead. There are voltages stamped near the connectors on this board.
Customer: replied 2 years ago.

I will try to do this later, otherwise will try tomorrow late afternoon.

Expert:  Aric replied 2 years ago.
Okay, simply reply back once you're able to.
Customer: replied 2 years ago.

It is hard to be objective in the ratings until we are closer to a solution to the problem. However I have again removed the back panel and tested the voltage 'out' from the main (large) board. I eventually found the connectors with the voltage out markings. 5.2v 12v and 24v.

the 5.2v out lead showed the correct voltage and this lead with many other leads went to the smaller board which has all the input sockets.

I have repeatedly tried connecting the power lead and the red/white indicator light continues to alternate every few seconds. A red led glows briefly under the optic signal socket at the same time as the main led indicator is red.

A website stated that if a 3.5mm headphone jack plug was repeatedly inserted it would clear the problem, which I tried to no avail.

Where do we go from here?

Expert:  adamd-mod replied 2 years ago.


It seems the professional has left this conversation. This happens occasionally, and it's usually because the professional thinks that someone else might be a better match for your question. I've been working hard to find a new professional to assist you with your question, but sometimes finding the right professional can take a little longer than expected.

I wonder whether you're OK with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.

Thanks for your patience,