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Old 11-09-2019, 03:22 PM   #1
newman25
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Default Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

Hello,

I'm checking out a TV that belongs to a neighbor and it has no picture/sound/backlight when turned on.

At this point I'm thinking that there is a problem with the power supply. There are no visible signs of bad capacitors. When disconnecting the cable to the main board the backlight does not come on as some suggested happens in other threads with similar sets/Power supplies.

Voltage readings on CNM803 (A13V pins) continuously fluctuate, I thought my meter was bad and grabbed my backup and had the same readings.

Checking through the resistors on the board I came across two at R9007 and R9008 that tested as open. I can't seem to locate a schematic for the BN44-00807A power board and being a tad color blind makes reading these bands tough. Do resistors normally fail because of another faulty component?

Attached are pictures.

I was considering just purchasing a replacement board but thought if I could replace a couple of faulty components cheaper I would give that a shot first so if anyone can help me troubleshoot this I would appreciate it.
Attached Images
File Type: jpg BN44-00807A.jpg (278.5 KB, 4 views)
File Type: jpg CNL802.jpg (402.7 KB, 3 views)
File Type: jpg CNM803 Pinout.jpg (383.4 KB, 3 views)
File Type: jpg R9007 R9008.jpg (367.2 KB, 8 views)
File Type: jpg R9007 R9008 - 2.jpg (380.1 KB, 4 views)
File Type: jpg Barcode.jpg (404.3 KB, 3 views)
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Old 11-09-2019, 03:52 PM   #2
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

Can we see the pictures of the whole board?
They are 39K resistors.
We also need to see the backside of the TV showing all the boards.
https://www.shopjimmy.com/samsung-bn...-led-board.htm
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Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
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Inverter testing using old CFL:
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TV Factory reset codes listing:
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Old 11-09-2019, 04:08 PM   #3
newman25
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

Here are the requested pictures.
Attached Images
File Type: jpg BN44-00807A Front.jpg (889.5 KB, 6 views)
File Type: jpg BN44-00807A Back.jpg (1.07 MB, 5 views)
File Type: jpg UN55JU6700FXZA TV Back.jpg (578.9 KB, 9 views)
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Old 11-09-2019, 04:24 PM   #4
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

They look like they could be 39k, you may need to disconnect one end of one of the resistors to get a accurate reading as they connect to the supply voltage from CM862/863

Try disconnecting CNM803 between the main board and power supply, plug in the tv and see if you get backlights

Last edited by R_J; 11-09-2019 at 05:02 PM..
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Old 11-09-2019, 07:01 PM   #5
newman25
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

I did pull one side of each of those resistors off the board and they still metered as open. I am assuming these are bad and should replace them but could there be another failed component that caused these resistors to fail?

Also, I power it up and removed the connector between the power supply and main board and the backlight did not come on.
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Old 11-09-2019, 07:26 PM   #6
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

What Ohms scale are you using?
Those two resistors (part of the backlights circcuit) are connected in series so the chance to have BOTH of them going open circuit is very slim, so please verify.
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Old 11-09-2019, 07:36 PM   #7
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

I kind of thought the same thing about them both going out at the same time...

I was using a new Klein meter that I bought several months ago but really haven't used much so I am not fluid on the settings. I just grabbed my old meter and tested them again with it and they both meter at 39k ohms each. Thanks for questioning that... I'm going to run out to the garage and grab the Klein again and see what setting I had wrong...

I ended up grabbing the Klein meter because I thought there was a problem with my old meter when I was checking the voltage at CNM803 and it was fluctuating so much but it metered the same way.
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Old 11-13-2019, 11:11 PM   #8
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

I've been searching for a schematic/service manual for this board but haven't had any luck out here on the net.

Does anyone know where i might be able to find one?

BN44-00807A

I ordered a replacement board but I'm not the type of person to give up easily on things and I would really like to see if I can figure out what's gone wrong.
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Old 11-14-2019, 04:04 AM   #9
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

Check your solder joints, look closely, it's easy to miss a bad/cold one.
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Old 11-14-2019, 05:13 PM   #10
newman25
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

I actually went through the board today and hit some of the major areas with the iron and re-flowed the solder and put it back into the TV. I tested the 13v and now have 12.88v and 3.28v at standby. When disconnecting the main board the backlight comes on as it should. So it looks like the power supply is working properly now.

But the bad news was when I then flipped it over the panel looks to have been cracked in the lower left side...

This TV was given to my neighbor from a friend at work and made the trek home in the back of his pickup. Either it was broken when he got it or it didn't travel well.

Anyway, thank you everyone for you help on this. This site has come through for me several times and it's members are top notch with their knowledge. So thanks again everyone and until the next one.....

Brian
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Old 11-14-2019, 09:03 PM   #11
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Default Re: Samsung UN55JU6700FXZA (TH01) / BN44-00807A Power Board

That's unfortunate, if someone is going to haul a tv home they may as well wrap it up like a baby, cuz they are fragile.
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