Panasonic Viera TC-L50EM60 Display Issues - Page 1
Forum section: electronics / repair

author: Hook
author_rank: Newbie
timestamp: May 29, 2019, 02:31:13 am
content: Hey Nerds!New Member to the Forum! So I will give a brief introduction. If you prefer to skip to the question then just read the next paragraph.I have been fascinated with electricity since I first stuck one of the old man's screwdrivers in the little crevice between the right side of the receptacle and the box and of course hot and ground have been sworn enemies since day one. That bright flash followed by the instant darkness sparked an interest. I didn't even flinch...I just smiled. Since that day I was always taking something apart. At age 12 I first laid my hands on a crummy 30w soldering iron and since that day I have always been tinkering with something.Now I need some assisting advice from the more "advanced" nerds in this community. My dad got himself a nice new 4K Smart TV and my dad handed his reasonably new Panasonic Viera from 2013 paid a pretty decent amount for it at the time. However, it was a demo unit at the local Wal-Mart and most likely already had many hours on it from the start.Then my Paternal Grandmother had developed agoraphobia and ended up running a couple hundred hours into it while she was taken care of. It worked perfectly up until about two years ago it started to hint it's troubling issue. Once in a while, It would display wacky colours before dying and then powering itself back on and returning to normal operation. Not a big deal.Anyways skip ahead to around February I had been using the TV with increased trouble but it was usable. (Starting to wonder if my dad got a new TV for THIS reason.) Then the issue became unavoidable. This was it's routine. Power on, crazy colours with a fuzzy picture, power off, power back on, work fine for about 10 seconds, then power off again. Rinse and repeat... I unplugged it took the back off inspected every board on it to find no obvious issues. And thats where it sits. My first thought was power supply, but with more advanced circuitry such as a TV, I can only assume.Hoping to breed more life into this TV provided it's not cost prohibitive. Any ideas?

author: Shock
author_rank: Super Contributor
timestamp: May 29, 2019, 04:10:20 am
content: TL;DR Panasonic Viera TC-L50EM60 LED TV with intermittent display and power cycling issues.Hi welcome to the forum. Funny you mention it was passed down to youbecause here you paid $900 for it.Careful if you are new to electronics that the TV is not connected to the mains outlet and you discharge the large capacitor safely before working on it. If it's outside your skill level take it to someone for repair.But anyway you describe a TV that has a ton of hours on it. Suspect the capacitors on the power supply board first, especially if any have domed tops that indicate they have failed due to age and heat causing high ESR. The way to test them properly before replacing is with an ESR meter. They are selling replacement boards however onebay it seems for about $30so this might be easier but double check part numbers first and there is no guarantee it will outright resolve the problem, or be a good working board.To go any further upload some high resolution photos of the boards especially the power supply in good light. You might also want to reconnect the cables in case you have an intermittent connection.For advanced players:The ESR of marginal capacitors reduces with heat, so if you warm the capacitors gently you may get a faulting power supply board operational enough for the TV to switch on. By then using freeze spray on the capacitors one by one while power cycling the TV you may be able to narrow in on defective capacitors.

author: Hook
author_rank: Newbie
timestamp: May 29, 2019, 05:32:59 am
content: Quote from: Shock on May 29, 2019, 04:10:20 amHa ha! Yeah I guess I wasn't in the mood to tell the story of the TV on that post.But yeah it is a "parental donation" in fact. They did pay $900 for it though back then.Anyways, you're right capacitor issues are as old as the electronics industry itself. After a close examination of the power supply board. I found one little electrolytic capacitor to have some sort of brown goo on top of it. I'm assuming its electrolyte. I can get some pictures later though.

author: cvanc
author_rank: Frequent Contributor
timestamp: May 29, 2019, 10:39:23 am
content: That capacitor does sound suspect.Also, pictures of the screen image showing the failure might be helpful. Many TV faults have a distinct pattern to them and that could be discussed here. Good luck getting it fixed.

author: Hook
author_rank: Newbie
timestamp: June 12, 2019, 05:52:29 am
content: After Recapping the entire board, I hooked it back up. Red light, no display. Solved that issue by discovering I had missed a capacitor. Replaced the vacant space. Back to the test bench...Powered it up...and to my demise I was greeted with the same issue.I got a little adventurous and started feeling components on the board with the unit powered up. I found that two components seemed a little warm. There is a heat sink with two TO-220 components hidden underneath. (Regulators I assume.) and a very low profile transformer/inductor of some sort. Here's a picture of the board itself.The components are clearly visible at the bottom of the image. They are diagonally across from each other. (The only piece of aluminum on the board.)

author: Dacke
author_rank: Regular Contributor
timestamp: June 13, 2019, 04:56:16 am
content: Quote from: Hook on June 12, 2019, 05:52:29 am"Chopper" FETs for driving the transformer. Please be careful with TV power supplies, as those heatsinks can occasionally have high voltage on them depending on the design. Check your output voltages, particularly the 5V.

author: Hook
author_rank: Newbie
timestamp: July 04, 2019, 04:05:39 pm
content: Quote from: Dacke on June 13, 2019, 04:56:16 am5V rail Reads between 5.09 and 5.1V and the 12V rail reads around 12.5 volts. With the power on.I guess I should also note is the TV is completely fine with the No Signal screen or a still image. As soon as you give it a moving input, then we get the issue.

author: Dacke
author_rank: Regular Contributor
timestamp: July 04, 2019, 04:39:26 pm
content: Not sure what inputs this TV has but I would check to see if this happens on all inputs. Put a signal into HDMI, Composite, Component, VGA, DVI, etc.Also this too -Quote from: cvanc on May 29, 2019, 10:39:23 am

author: Hook
author_rank: Newbie
timestamp: July 04, 2019, 09:17:01 pm
content: Quote from: Dacke on July 04, 2019, 04:39:26 pmComposite, HDMI, Component, VGA even Coaxial.As for the image, I pull out my crappy Casio Exilim and as soon as I do so... The TV decides to avoid displaying said colour pattern. Typical.I managed to catch it displaying said issue in a more clear way. However, I missed the full blown lightshow by a fraction of a second...aaaand Hello! Mr. Flash! It never did it again after that.

author: Dacke
author_rank: Regular Contributor
timestamp: July 05, 2019, 11:44:36 pm
content: Seems most likely to be a main board issue. Power supply and LED backlight driver are pretty much ruled out. T-CON board not likely simply because a failure in that board usually results distortion, lines, or issues in only one area or side of the screen (right, left, top, or bottom). A failure in the MCU / DSP effects the entire screen in my experience. Some easy things you can try is re-seating the LVDS cable, a flat cable from the mainboard to the T-CON board. You can also try pressing on the end where the socket is or gently wiggling it while the TV is turned on to see if it has an effect. It helps also when troubleshooting a large TV to have a mirror so you can watch the screen while you're troubleshooting from the back. Gently pushing on different areas of the main board with something that is not metal while the TV is on can expose faults as well, as can freeze spray. Make sure all connections are well seated, and all screws that mount any boards to the chassis are tight (bad grounds can cause all kinds of issues). Check connections to the T-CON board as well, just in case.After this if you don't make any progress you may be either attempting component level repair on the main board which can be difficult, or possibly just replacing it. And even if you replace it, there's no guarantee that it will work as any board you are likely to get will be used (not sure how old this TV is).