LG 42LK450 front touch buttons not working

[oharal]

Hello everyone. A couple months ago my LG tv got knocked out after some clown in his single engine airplane ripped down some power lines between my house and a nearby uncontrolled airport. The little red standby light was on but the tv wouldn't turn on. I called LG support and they told me the main board needed to be replaced and they gave me a part number for it. This part number was out of stock at every online retailer under the sun but some places had listed a new apparently updated part which I bought. It didn't fix it so I sent it back. I then took it to a professional TV repairman and he showed me the PS was still good and it did indeed need a new main board. His cost to fix it was more than I paid for the TV so I passed. Back to eBay I went to buy the part number LG had given me... They sent a part for a 42LK520 which didn't work and had a different part number on the sticker. So I sent that one back and bought another one being careful to verify it was the exact board for my TV. So yesterday I put this new board in and plugged in the TV and immediately the set powers up without touching the on button and plays static and shows the menu to configure the TV so the video goodies are working but the touch buttons on the front don't work so I can't do anything with it yet. Any ideas TV pros? A little background on me, I am graduating with my degree in electrical engineering in December and am therefore experienced with troubleshooting and multimeter use and electronics jargon so don't hold back. My problem is I know nothing of how these TVs work!

Thanks!

[oharal]

Re: LG 42LK450 front touch buttons not working

This one has to be an easy one for someone who knows a ton about TVs!

[budm]

Re: LG 42LK450 front touch buttons not working

https://www.badcaps.net/forum/showthread.php?t=39740
There are more than one versions of this model:
http://www.shopjimmy.com/catalogsear...t/?q=LG+42LK45
So which one are your original boards?

[oharal]

Re: LG 42LK450 front touch buttons not working

http://www.shopjimmy.com/lg-ebr61369...42lk520-ua.htm

This is the main board model I have, EBR61369602. Would you like me to upload some pictures of my hardware as well?

[budm]

Re: LG 42LK450 front touch buttons not working

I would like to see the whole back side of the TV so we can see how all the boards are connected.

[oharal]

Re: LG 42LK450 front touch buttons not working

[oharal]

Re: LG 42LK450 front touch buttons not working

Let me know if you want to see anything else at all. Its no problem to get more pics.

[budm]

Re: LG 42LK450 front touch buttons not working

Can the TV be controlled by the remote?

[oharal]

Re: LG 42LK450 front touch buttons not working

My batteries leaked a while back and got the contacts all nasty in the battery compartment but I don't have anything here in my apartment to clean them with so it isn't working right now.

[oharal]

Re: LG 42LK450 front touch buttons not working

Anyone got some tips? Any help is greatly appreciated!

[oharal]

Re: LG 42LK450 front touch buttons not working

Bump

[reaper57]

Re: LG 42LK450 front touch buttons not working

Try cleaning the contacts on the remote with coke if you can. Otherwise don't you have anything to use at the shcool you go to? If you study electronics they should have something for cleaning flux which should work. Also going over the contacts with a soldering iron and a bit of flux on them, maybe even some solder, should be a good way to fix them.

[reaper57]

Re: LG 42LK450 front touch buttons not working

I forgot to mention try taking the board with the touch buttons off, test them with a multimeter and if they are ok, try shorting the pins with something to see if they work. If they do then the problems is just the touch sensor if not it's probably a cable or the logic board. If the buttons work you might want to try to solder wires from the butons directly to the board (but you will need a pinout for that and I'm not sure how you are going to get the sensors working).

[oharal]

Re: LG 42LK450 front touch buttons not working

I'll look into something at school to clean the remote contacts.

That's the thing about the buttons...how do I test them to see if they're working? I assume a touch button is nothing like a regular button (capacitive I guess?) When the button is touched does it supply one voltage like a regular button (ON/OFF) or does it send a specific signal to the main board? I see the names of the pins for the connector but there isn't a pin just for each button so I assume one pin takes the inputs from all the buttons which makes me think there must be a specific signal coming from the button board to tell the main board which one was touched.

[budm]

Re: LG 42LK450 front touch buttons not working

That is why we need to see if the remote will control the TV OK, if it does, then we will need to look at the touch control board. Can you get to that assembly?

[oharal]

Re: LG 42LK450 front touch buttons not working

Gotcha. I can get to it, yes. I tried taking it out yesterday just to see it but I need three hands and my brother wasn't around to help.

[budm]

Re: LG 42LK450 front touch buttons not working

And if there is the problem in the touch control panel, it may also lock out the remote function, I cannot tell if the remote receiver sensor is on the same board as the touch control panel or not, if the remote does not work then you can disconnect the touch panel and see if the remote will work.

[oharal]

Re: LG 42LK450 front touch buttons not working

Yeah it looks like the remote sensor is in the touch panel board. There is a pin called IR in the connector so if I disconnect the touch panel the remote won't work unless I'm confused.

[budm]

Re: LG 42LK450 front touch buttons not working

Can we see the pictures of the board then there may be a test points I can suggest to see if there is any activity when the touch control is activated?

[truep]

Re: LG 42LK450 front touch buttons not working

I haven't looked it up but usually IR/button boards are cheap because they rarely fail. since the Power supply comes it must be getting PS-on, I still think the problem is in the main board unless the Button board fixes it.