Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

[budm]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

BTW, when you removed that MOSFET on the heatsink, that MOSFET is for PFC Voltage booster, when you put it back are you getting 380 ~ 400VDC Voltage (measure between the legs of the cap) on the main 450VDC filter cap legs?

[Topcat]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

BTW, when you removed that MOSFET on the heatsink, that MOSFET is for PFC Voltage booster, when you put it back are you getting 380 ~ 400VDC Voltage (measure between the legs of the cap) on the main 450VDC filter cap legs?

I did not do any voltage measurements with that mosfet removed, I just checked it for shorts and removed it to identify it....it was mounted funny; face down. The only way to identify it was to desolder it. If you want measurements with it removed, I surely can.

[budm]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

What I mean is that after you solder it back into the board, is the PFC Boost Voltage still present or not.
BTW, I also forget to ask if the 3.3V is going up and down when you run the power supply board by itself or not without anything connected it but just AC cord.

[Topcat]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

BTW, I also forget to ask if the 3.3V is going up and down when you run the power supply board by itself or not without anything connected it but just AC cord.

Yes, it does... in sync with the faint 'chirp' I hear that's also in time with the blinking STBY/Power LED...

[budm]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

can you pin point where the chirp is from?
Since the 14V standby power supply is stable, there must be the problem some where in the step down power supplies/loads that is going on and off.

[R_J]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

What are the numbers on IC9101, I see voltage test points around it, like A_12v (always 12 volts) Is the A12V stable? I suspect the A_12V supplies other ldo's. I see what look like many ldo regulators in the picture with the heat sink removed.

[Topcat]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

Sorry for the delay, fellas.....I had to slide this aside to work on some other stuff....but I've got this one back on the bench.

can you pin point where the chirp is from?
Since the 14V standby power supply is stable, there must be the problem some where in the step down power supplies/loads that is going on and off.

With the naked ear, no....it's very faint. I need to find my old stethoscope....it got lost in the garage (also good for finding boost leaks and vacuum hissing in cars).

What are the numbers on IC9101, I see voltage test points around it, like A_12v (always 12 volts) Is the A12V stable? I suspect the A_12V supplies other ldo's. I see what look like many ldo regulators in the picture with the heat sink removed.

It's marked:

Line 1: SLM4281A
Line 2: 1833

[R_J]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

IC9101 has no datasheet, so I don't know if it has anything to do with the voltages in that area. You said the 14 volts is stable, did you check if any of the other sub voltages are also stable ie: A_12V

[Topcat]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

IC9101 has no datasheet, so I don't know if it has anything to do with the voltages in that area. You said the 14 volts is stable, did you check if any of the other sub voltages are also stable ie: A_12V

There is 12.5~12.9v there, drops/fluctuates ~.5v with the 'chirp'. With the aid of a stethoscope, the 'chirp' seems to be coming from TP801CS....but it's very faint, so I can't guarantee that....but that's where it was the loudest.

https://www.badcaps.net/forum/attach...1&d=1620847524

[SMDFlea]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

It's marked:

Line 1: SLM4281A
Line 2: 1833

How many pins are there on that IC ?

[Topcat]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

how many pins are there on that ic ?

16.

[SMDFlea]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

16.

Samsung use renamed Magnachip parts afaik, it could be a MAP3249 ,its the only 4-channel LED 16 pin IC listed on their site: https://cdn.badcaps-static.com/pdfs/...74f7b75b74.pdf

.

[basementtech]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

Hello Topcat , did you ever do any good with this samsung ? I have the exact tv with same issues . thank you

[Topcat]

Re: Samsung UN43NU6900FXZA 43" 4K - Power Supply Issue

Hello Topcat , did you ever do any good with this samsung ? I have the exact tv with same issues . thank you

No, I never did figure it out. I reassembled it and shelfed it hoping maybe I'd encounter one someday with a broken screen but a good board. It must be a common problem, there are no used boards anywhere for this thing.

[Protractor_4transisters]

Good day:

I am looking for a Service manual and schematic for this same model TV (UN43NU6900FXZA). I also have a power supply issue. No standby light, the fuse on the board is good, and about 170 volts is getting to the MOSFET (60R360QS), that same 170 Volts (DC) is at the transformer. I removed the MOSFET and tested it and other than having a high RDS of .7 ohms, ( I can't find a exact match datasheet for the MOSFET). I can only find a datasheet for a 60R360Q., that datasheet calls for an RDS of .36. I think it maybe OK? Oh and also the TV is about 5 years old and I noticed maybe after about a year of use the TV would go blank for a few seconds every now and again and then come back on in a second or two or three (Now the TV is dead). Any help would great.

Thanks

[nomoresonys]

[QUOTE=Protractor_4transisters;n3166147]Good day:

I am looking for a Service manual and schematic for this same model TV (UN43NU6900FXZA). I also have a power supply issue. No standby light, the fuse on the board is good, and about 170 volts is getting to the MOSFET (60R360QS), that same 170 Volts (DC) is at the transformer. I removed the MOSFET and tested it and other than having a high RDS of .7 ohms, ( I can't find a exact match datasheet for the MOSFET). I can only find a datasheet for a 60R360Q., that datasheet calls for an RDS of .36. I think it maybe OK? Oh and also the TV is about 5 years old and I noticed maybe after about a year of use the TV would go blank for a few seconds every now and again and then come back on in a second or two or three (Now the TV is dead). Any help would great.

I would check the solder joints on the powerboard and the electrolytic capacitors.

[Protractor_4transisters]

I would check the solder joints on the powerboard and the electrolytic capacitors.

I have tested all the capacitors (in-circuit) they all test (and look) good. I have not tested the ESR of the caps. though. Maybe I should just recap. the power section of the board? Any thoughts on that.

[nomoresonys]

That would eliminate them as suspects.

[Topcat]

I have tested all the capacitors (in-circuit) they all test (and look) good. I have not tested the ESR of the caps. though. Maybe I should just recap. the power section of the board? Any thoughts on that.

FWIW, I checked all those caps on my LCR. They were fine.