Dead 75" Samsung 4k TV Repair UN75NU6900FXZA
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- Опубліковано 21 жов 2022
- We fix a dead 4K Samsung TV UN75NU6900FXZA with power supply BN44-00874C.
Do you have this power supply and need us to fix it? Check out the link below:
nickselectronics.com/products...
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Hello,
The 75-inch SAMSUNG TV 75au8000 or 75au9000
LED strips are getting very hot, making it impossible to touch them with hands, even emitting smoke. The old LED strips burned the diffuser sheet. I reduced the brightness using the energy-saving function, but the LED strips still heat up significantly. I checked the resistors on the board, everything is fine, and the transistors are intact. There are 218 volts on each of the four LED strips. The marking on the strips is 94V S1A8-750SM0-R0.
Supply board is BN44-01112A
I've seen many similar issues online. People are returning their TVs under warranty because they're afraid they might cause a fire. Thank you so much for your work; I've learned a lot from your channel!
Wow, that's kind of crazy. I didn't know this was an issue with the AU8000 and AU9000 series. This must be a new thing or they are still under warranty perhaps. I will be keeping an eye out in case one comes into our shop for repair.
@@NicksTVRepair
Also, be cautious with ordering new LED strips. After I ordered mine, they only worked at half capacity, but at least they didn't get hot. The brightness was so low that the image was only visible in a dark room. This was because the LED strip connector has 4 contacts, 2 negative and 2 positive. But from the board, only 3 wires are coming according to the “- - +” scheme, and this positive has 220V. The thing is, the old LED strip lights up all the diodes at once (I only have one left in working condition) and also has 2 negative and 2 positive contacts, like the new one, but the power (positive) from the three wires from the power board, according to the “- - +” scheme, when connected, is divided into 2 positive pins at 110V each as they are connected according to the “- - ++” scheme or HL+ L- H-. But the old strip gets very hot when current is applied to all the LEDs. I couldn't find the same strips as the original, but I managed to modify the new strips by simply connecting two positive pins, thus I achieved the same principle as the old strips. However, they also get very hot, and I'm afraid I need to keep looking. In this regard, I have a question for you, I would be very grateful if you could help me with this. Should I reduce the current going to the LED strips by adding a resistor? It's also a mystery to me why, when the lights are turned on halfway at 220V, they don’t get as hot as when I turn on the second row of lights according to the HL+ L- H- scheme (like in the original LED strip).And also, why do I need 2 negative wires if I only have 1 positive? I can't understand this. Maybe it's worth looking in this direction and removing one of the negative wires from the board... I don't know.
P.S. I was very surprised by Samsung's response that this is not a problem and that the TV should be watched with a time limit because of this
You could reduce the current but I would also just advise an easier method is to go in the TV settings and lower the backlight brightness to 50% or 75% and it would have the same effect.
You are absolute right,I did not explain correctly ,i have never found only the cap blown apart ,always seen it when the mosfets fails (short).
We see that with a Vizio power supply as well, it's the same thing, 50% of the time the cap is blown 50% of the time it is in perfect condition. I don't know what the difference is in terms of how the mosfet or diode shorts out to cause that or not. I would be interested in knowing though.
I actually did a video recently on that exact Vizio board. This is the one here
g.page/r/CYoJT4T-14qTEAg/review
Thanks! I was given one of these TV's as junk. Can't wait to test and repair. I used to repair an old Sony rear projector every couple years when it failed to focus. A regular occurance.
Those are for sure not junk TV's. Especially if you have the exact model UN75U6900FXZA. Definitely worth fixing.
@@NicksTVRepair Yes that's my model, it's huge. I have the back off. I'll test the components tonight. unplugging the data ribbon cable from the power board did not make the backlight come on like some older, smaller models (while power is plugged in).
Hi Nick. I replaced these, and the fuse blew again, and the 'center' mosfet. I unplugged the sound board ribbon, power board now isolated, and a 2nd fuse blew. What else could I check? I suspect a lightning strike.
@@WizardOfWhoopee Any luck repairing? I had a lightning strike and my fuse and mosfet blew. Changed both mosfets and fuse and fuse still blows. Mosfet is shorted again.
@@cutum Mine did the exact same thing. The repair kit kept blowing. I'm ready to buy a whole new board. There were None in Dec/Jan. Now there's a flood of new ones on ebay for around 150 bucks.
This was super helpful! Needing some rookie info....Do you have the part numbers you used for the Fuse replacement and Transistor replacements? You mention the Samsung parts numbers but I didn't here what you replaced them with. There seems to be quite a variety of these when I look at Digikey.
This is the 2 throughole mosfets we used in the video:
MMF60R190Q
They are rated for 600V and 20Amps. They are N-channel MOSFETS.
Lots of compatible replacements avaialable.
If you call Digikey they have techs that can help you find compatible alternatives.
As for the fuse it says on the board it is a 6.3amp 250V. It's a ceramic fuse, and I believe they are slow blow.
If digikey doesn't have them, check mouser, and if you still have issues, then just go to eBay, someone there should have what you need.
O super
2:56 What would you recommend as a replacement for those original MagnaChip MMF60R190Q N-ch MOSFETs? Thx
Doesn't matter really as long as it is an N-channel Mosfet that can handle 600V at 20A. I said 600v in the video technically the originals can handle up to 650v but the power supply never puts that kind of voltage on them. I don't believe it ever goes about 450 at peak actually.
We use TK20A60U
Good worck broooo
Thank you
My 2 cents,I have done a few of those and in almost all of then I have found capacitor CP809 (101K/1K) blown apart and is found in front of diode DP801Cs in the same heatsink of the 2 mosfets,so is a good tecnique always verify this cap.
Jorge
I could be wrong, but I believe those will typically fail due to the diode or the transistor shorting out, I don't think that cap blows on it's own.
Have you seen one of these with only CP809 go out? If so then yes, it would absolutely be wise to replace it everytime.
Haven't had one of these come back yet even with the 1 year warranty, so I assume it's most likely something that only occurs at the time of failure but if the cap is okay then it won't go bad later after replacing the other defective components.
What is the little blue thing next to the transistor that you are replacing? On my tv with the same board the blue thing next to it burned up.
That is a ceramic capacitor.
If you want to fix the board yourself and want a one stop shop to get all the parts you need we have a repair kit for sale that includes the capacitors. Here is a link to the kit:
nickselectronics.com/products/bn44-00874cpartskit
Is click of transformer normal when truning on tv? btw I really like your videos
Usually what you hear click is a relay and yes that is normal.
Thank you for the nice comment!
Surprised you don't check gate and drive components.
No need when you have seen these boards a hundred times and it's always the same exact failure.
@@NicksTVRepair I realize this is a specific board that doesn't take out the driver and other components. I just think you should mention that FET failures can cause other components to fail and is good practice to check before powering up.
This is true
Ill make sure to do that moving forward.
There are a few other power supply boards we are going to repair on camera that are more involved and require a lot more parts to be replaced and repaired, ill make sure to mention that.