Toshiba 50" 50L3400U blinking backlight

[ngth82]

Re: Toshiba 50" 50L3400U blinking backlight

The part number should be V500H1-ME1-TLEM9.

I went ahead and purchased the LED strip from eBay. It'll arrive in 2-3 weeks. I'll take the TV apart around Christmas.

https://www.ebay.com/itm/201707864932

[sXc31]

Re: Toshiba 50" 50L3400U blinking backlight

Hi ngth82. If u would conciser repairing TVs in the future u should buy individual LED bulbs and re-soldering yourself because them lads that are selling the strips are EXPENSIVE as hell> just shelve few of a kind of them in the drawer.
Hope new strips will sort the problem, Cheers.

[ngth82]

Re: Toshiba 50" 50L3400U blinking backlight

Hi ngth82. If u would conciser repairing TVs in the future u should buy individual LED bulbs and re-soldering yourself because them lads that are selling the strips are EXPENSIVE as hell> just shelve few of a kind of them in the drawer.
Hope new strips will sort the problem, Cheers.

I thought about it... but I didn’t want t Just replace the LED and break the strip. I agree that the discrete pieces are way cheaper — looks like 100 pcs of white leds for about $10. :/

I typically don’t like picking up units with backlight issues since the screen is fragile. But I couldn’t resist on this unit since it’s newer and the unit is very thin.

I hope it works too!

[ngth82]

Re: Toshiba 50" 50L3400U blinking backlight

In the continuing saga: The replacement LED strip came in. I powered it up and looks like only 1/4 of the LEDs turn on. They tested just fine on the lab bench supply, but the TV doesn't turn them all on.

If i press on the LED strip, i can get them to faintly glow. I've requested a new unit from the eBay seller.

I also have a second LED driver IC and will try replacing it again this evening.

[ngth82]

Re: Toshiba 50" 50L3400U blinking backlight

Hi All -

I started this thread July 2016. I just wanted to give a quick update on the TV.

I received a second replacement LED strip two weeks ago. i finally had the opportunity to install it today. The TV appears to be working.

Project Summary:
- Received free TV July 2016
- Discovered backlights blink when the brightness is above ~75%.
- Used TV as-is for over a year as our family picture frame; during that time, I had to reduce the brightness to ~50%
- October 2017 - Purchased replacement LED driver - replaced - didn't change behavior
- November 2017 - Purchased replacement LED strip (granted, I should have just replaced the 10 bad LEDs). Replacement unit didn't work.
- January 2018 - Second replacement LED strip received.


TV fixed!

I'll post a long term update on the unit. I may keep it.
(Or i may end up selling it since i have 7 other TVs in the garage to fix!)

[scottydoo]

Re: Toshiba 50" 50L3400U blinking backlight

Thanks for your info and updates. I just wanted to let you know that I appreciate your work and I'm interested in any of your future updates regarding your TV.
I'm having the same blinking backlight problem with my 50L1400U. It uses the same LED strip. For anyone out there with a 50L1400U, I've ordered a new LED strip and I'm going to install that. I'm also adding a better heatsink per this YouTube video. https://www.youtube.com/watch?v=wskWbH4TOyA
I'll follow up when I've installed the new parts.

[ngth82]

Re: Toshiba 50" 50L3400U blinking backlight

Cool. I'm glad to hear this thread has helped you.

I'd be a bit weary of using a smaller heatsink. The one that come stock with the PS board is larger and directly attaches to the PS GND plane for additional dissipation potential.

I ended up using the original heatsink, but with a good quality thermal paste.

I kept the TV. It's mounted on the wall and being used for our Xbox One/Xbox 360/Wii setup downstairs.

Thanks for your info and updates. I just wanted to let you know that I appreciate your work and I'm interested in any of your future updates regarding your TV.
I'm having the same blinking backlight problem with my 50L1400U. It uses the same LED strip. For anyone out there with a 50L1400U, I've ordered a new LED strip and I'm going to install that. I'm also adding a better heatsink per this YouTube video. https://www.youtube.com/watch?v=wskWbH4TOyA
I'll follow up when I've installed the new parts.

[scottydoo]

Re: Toshiba 50" 50L3400U blinking backlight

My TV is working great now. I added a heatsink that I salvaged from an old broken laptop.

The original heatsink looked fine on my TV and it looked like the thermal paste was still doing its job, so I didn't remove the original heatsink. I've decided that it was just not enough to dissipate all of the heat that is being created. (I don't know why the heat problems are occurring now vs. when the TV was new, but that is beside the point.)

The salvaged heatsink is copper and includes a heat pipe. I had to cut away some of the salvaged heatsink with my Dremel®, but I was able to make it fit on top of the original heatsink. I used thermal paste between the original and salvaged heatsink. I then drilled some small holes in the sides of the original heatsink and used screws from the broken laptop to secure the salvaged heatsink to the original. Now everything is working great. Sometimes I feel the back of the TV and it's warm where the salvaged heatsink is located, so I know it's doing its job.

Today I received my new backlight from China. Maybe I'll install that someday, but as long as it's working I don't think I'll worry about it.

P.S. In order to test my new setup I had my children watch Peter Pan on DVD. Something about that DVD really heats up my TV. Whenever they tried to watch it before I installed the salvaged heatsink the TV would always start to blink about every 10 seconds. (I think it has something to do with the show being 4:3 and having large black bars on both sides of the picture, but that's just a guess.) Now when they watch Peter Pan the back of the TV gets warm, but the TV never blinks. Go figure...

[ngth82]

Re: Toshiba 50" 50L3400U blinking backlight

Glad to hear that worked out for you!

Seems like there are two well documented failure modes for this tv:
1) poor thermal dissipation from the LED driver
2) a bad LED string

For me, it was clearly a bad LED string :/. The Replacement LED string is still operating strong!

Best of luck!