Samsung smart tv with black screen of death

[jsean]

My Samsung smart tv that’s about 5 years old just went kaput. It seems to be in an endless power on/off cycle. Backlight is light, but no video or audio. Unable to control it by the remote or the power button at the back. TV doesn’t have a separate t con board.

Did some trouble shooting by the taking off the back panel. Here are the steps I’ve done thus far:
1. Confirmed that the backlight stays constantly on if I disconnect the cable from the power board to the main board.
2. Disconnecting the 2 LVDS cables to the the led array at the bottom doesn’t make a difference. Whether it’s 0, 1 or 2 of these plugged in, as long as the cable from the power board to the main board is connected- it’s doing the same thing.
3. Unplugging the LVDS one by one doesn’t cause half the screen to light like some people do. So that makes me think it’s not an array issue?
3. I took the heat shield of the main micro and the regulator (I think?) on the micro gets up to 149-150F within a minute or two of the repeated power cycles.
4. I tried de-pinning the “power blu” pin on the cable from the power board to main board and that didn’t do anything (someone on YT had luck with that, so whatever).

All of the above makes me think the main board is toast. The replacement part is BN94-12662G which seems to be out of stock at shopjimmy and a couple of other stores I’ve used before.

Anyone know if I can swap in a main board from a different model 50” Samsung tv? Or if there’s any other way to fix this thing up?

 

[skyactiv]

Copy & paste the part number and type fits in the search engine BN94-12662G fits

 

[SeaJay]

They are throw aways IMO.

 

[Malo83]

Time to step up to Sony.

 

[Rand]

While the part doesn't look horribly expensive. There is no certainty it would fix the problem.
I'd probably take the opportunity to upgrade.

 

[brianl703]

Cycling power makes me think the power supply board is at fault. Measure the output voltages from the power supply board and make sure they are correct and stable. Do this with the main board connected to the power supply board.

 

[skyactiv]

Why Samsung?

I was researching buying a new TV a week before the Super Bowl when they were on sale.

Rtings.com says most don't offer good value and aren't worth buying. Their high-end TVs are usually among the best TVs on the market, and for the most part, they're competitively priced. Their entry-level and mid-range models are a different story, though, as most offer lackluster picture quality and are overpriced.

I have a Sony 55" I moved into my new Home that is too small as it's further away. I didn't buy anything yet.

 

[y_p_w]

While the part doesn't look horribly expensive. There is no certainty it would fix the problem.
I'd probably take the opportunity to upgrade.

Might be interesting as a DIY exercise, even if it doesn't work.

But after a few years that's probably just a few years closer to when APIs stop working. But it might be good to have a backup.

 

[skyactiv]

The 6 Best TV Brands - Winter 2023: Reviews

Shopping for a new TV can be challenging; with so many different models out there, it can be hard to know which is the best TV brand and where to start.

www.rtings.com

 

[himemsys]

Cycling power makes me think the power supply board is at fault. Measure the output voltages from the power supply board and make sure they are correct and stable. Do this with the main board connected to the power supply board.

I recently had similar symptoms on an older, cheaper LCD TV. It would turn on, but almost immediately turn back off. I found the power supply board and noticed one of the FETs screwed to the heatsink had a blackened mess around it. The part was obsolete but found it on ebay shipped from Malaysia for about $15. It took a couple of weeks to arrive, but ended up fixing the problem. It's now a spare TV but at least it's not taking up space in a landfill.

 

[JavierH19]

probably not. But thats a shame. Have a 16 year old cheap samsung lcd that still works. Recently bought an 85 inch 4k samsung on sale for 899. But the chance of it getting fixed for a reasonable price is nil. I'd just junk it and buy something else. Still 5 years is ok if it was a cheap low end model.

 

[jsean]

Cycling power makes me think the power supply board is at fault. Measure the output voltages from the power supply board and make sure they are correct and stable. Do this with the main board connected to the power supply board.

That’s an interesting thought. I was initially leaning towards the power supply board being at fault. But 2 things make me pause:
1. With the main board disconnected, the power supply board is able to keep the backlights running constantly.
2. At the connector (CNM803) leading from the power board to the main board, I’m getting 12.79V constant across the pins. The pins are spec’Ed to 13V. YT videos show folks getting anywhere between 12.78 and 12.84V based on the videos I saw. So it seems reasonable. The values drop when it power cycles but holds steady otherwise.

 

[jsean]

Time to step up to Sony.

Funny thing, I got a backup 32” Sony LCD tv that’s going on 15 years and it runs just fine. Won’t be getting another Samsung that’s for sure

 

[jsean]

.

 

[jsean]

While the part doesn't look horribly expensive. There is no certainty it would fix the problem.
I'd probably take the opportunity to upgrade.

Did you happen to find it in stock anywhere?It shows up as out of stock everywhere I’ve looked, but I could be not looking at the right spots

 

[Rand]

ebay has used ones.

BN94-12662G - Google Search

You can get a better 55" tv for under $300

 

[jsean]

probably not. But thats a shame. Have a 16 year old cheap samsung lcd that still works. Recently bought an 85 inch 4k samsung on sale for 899. But the chance of it getting fixed for a reasonable price is nil. I'd just junk it and buy something else. Still 5 years is ok if it was a cheap low end model.

I had to look through my purchase history. I spent $450 on this things as a Thanksgiving sale special for 4K UHD. It’s well rated too on BB: TV link

 

[JavierH19]

I had to look through my purchase history. I spent $450 on this things as a Thanksgiving sale special for 4K UHD. It’s well rated too on BB: TV link

For 450 I'd be ok with it lasting 5 years. Now if it was over a thousand then I'd be upset. I think I spent about 600 on my really old Samsung. It's 1080p but it's still going strong in the guest room for when visitors come.

 

[CarLuver]

ebay has used ones.

BN94-12662G - Google Search

You can get a better 55" tv for under $300

Costco in my area has a Hisense 55 inch with a 3 year warranty on sale for $259 . i would toss the old one and just get a new one

 

[xspeedy]

Try cooking the main board in the oven if you can bear the smell. I had an old LG TV where the HDMI ports failed. It was that the solder joints broke over time and the oven reflowed the solder to restore the connections. Might be worth it for ****s and giggles before you toss it.