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Shahid
Shahid, Technician
Category: TV
Satisfied Customers: 9465
Experience:  I have been repairing electronic gear since 1993 as a qualified Sony tech
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I have a Samsung LN52B750 that is 7 years old. I found this

Customer Question

I have a Samsung LN52B750 that is 7 years old. I found this link but its not really my problem. But for reference http://www.justanswer.com/tv-repair/5yexd-samsung-ln52b750-tv-2-1-2-yrs-old-just.html
JA: What's the model number of your TV? How old is it?
Customer: On my TV the stand by light just flashes on then off
JA: Does the TV menu work? Do you have the same problem on all sources/inputs?
Customer: it does not turn on...using the remote or the on button on the tv
JA: How long has this been an issue? What happened right before this popped up?
Customer: few days... I turned it off and came home from work and tried to turn it on
JA: Anything else you want the tv expert to know before I connect you?
Customer: when I disconnect the cable from the input board to the power supply the TV lights up...so I think my screen and power supply are working
Submitted: 28 days ago.
Category: TV
Expert:  Aric replied 28 days ago.

Hello, Sorry you're having problems. Even the smallest detail in the symptoms changes the diagnosis so we do not generally eve refer to another question. I'd rather address your problem as an independent one to get you an accurate answer.

Now, regarding the power light- does it only flash ON and then OFF after you press the power button?

Also, are you saying you have the back of the set removed right now and are referring to disconnecting the ribbons from the Mainboard causes the screen to light up?

Expert:  Aric replied 28 days ago.

Please review my reply and postback to proceed.

Customer: replied 28 days ago.
regarding the power light ..yes that's all it does is flash off and on and the back of the tv is off and I am referring to the ribbon cable that goes to the board with the hdmi inputs etc...if that is the main board it goes between that and the power supply
Expert:  Aric replied 28 days ago.

Yes that is the Mainboard. WRT to the power light, what I asked was if it blinked ONLY after you press the power button, while you held the power button- WHEN does it blink please?

Customer: replied 28 days ago.
only after I press the button... if you press it and leave your finger on it. It will continue to flash off and on
Expert:  Aric replied 28 days ago.

Perfect. And just to make sure- NO backlight from the screen wen you press the power button. That ONLY occurs when you disconnect the ribbon cable, correct?

Customer: replied 28 days ago.
correct
Expert:  Aric replied 28 days ago.

Okay thanks. What you have here is a faulty Mainboard in the set then (the AV Input board) and will need to replace that board to fix the issue. It provides the turn on command to the set (which you don't have) and the Samsung tech notes for this set state to disconnect the ribbon, check for backlights and this determines if the fault is the power supply (no lights) or Mainboard (screen lights).

Expert:  Aric replied 28 days ago.

It seems the Mainboard for this model, has been unavailable for quite some time now. It does not even show as "Out of stock" anymore- simply does not show up in a search. That said if you want to TRY to procure a Mainboard, then your only hope is going to be to pull the PART number off of the board in your set and Google it to try and find a match (Samsung has been known to use the exact same board across different models).

Customer: replied 28 days ago.
is the part available BN-01149a and is that the right part number
Expert:  Aric replied 28 days ago.

Doesn't look like you have enough numbers there, but a quick Google search of the number you posted pulls up this (which has those numbers in it - but also some more).Visually inspect the board and compare and also look for any other numbers/letters that may match:

http://I'm not sure if you're having problems replying? Please don't try to reply to the e-mail the site sends you. Instead use the link to get to the site page and reply here.

Customer: replied 28 days ago.
will it be on the sticker or printed on the board.. I can up load the photos
Expert:  Aric replied 28 days ago.

You can also post a picture of your board if you'd like, but it will need to be a high quality HD picture in order for me to be able to read the part/board number.

Expert:  Aric replied 28 days ago.

Do you need further assistance with this?

Expert:  Aric replied 28 days ago.

If you need further assistance let me know. Before you go, PLEASE DO click at least a 3 STAR RATING, at the top of your screen. That is how I am credited for my efforts by the site. You can follow up any time as needed at no additional cost.

Customer: replied 28 days ago.
I will upload the photos of the sticker .. there is one over the top of another one I have both
Expert:  Aric replied 28 days ago.

Okay sounds good.

Customer: replied 28 days ago.
here are the stickers from the board
Expert:  Aric replied 28 days ago.

Does that board I posted above appear VISUALLY the same as your board?

Expert:  Aric replied 28 days ago.

I'm asking because the part number matches, but I cant see an overall picture of your Mainboard.

Expert:  Aric replied 28 days ago.

Do you need further assistance with this?

Customer: replied 28 days ago.
ill take a photo of the whole board for you to view
Expert:  Aric replied 28 days ago.

Okay sounds good.

Customer: replied 28 days ago.
here is the full main board
Expert:  Aric replied 28 days ago.

I'm sorry I can't match up all of the part numbers between these. I will opt out at this point.

Customer: replied 28 days ago.
the part number printed on the board matches ... the stickers on the board the white oneBN97-03102B and the yellow one BN94-02686B.
What do they indicate upgrades to the boards the white being the original and the yellow being the latest. Determining if they are upgrade or just part number changes(board modifications) is the key correct.
If the stickers do not match there is always a chance it will not work. or maybe will not work as it did or will the difference be minor
Expert:  Shahid replied 28 days ago.

Hello, I'm Shahid. Sorry to hear that you're having trouble with this but I'll do my best to help.

- Could you please get me the complete model number/code written on back of TV?

These info will help to assist you further.
Thank you.

Customer: replied 17 days ago.
LN52B750U1FXFXZA
Expert:  Shahid replied 17 days ago.

Thanks for TV model number info. TV needs main board replacement.

Correct part number of main board is BN94-02585B which is available at following suppliers..

http://www.searspartsdirect.com/part-number/BN94-02585B/0057/528.html?pathTaken=partSearch&q=BN94-02585B

http://www.samsungparts.com/Products/Parts_and_Accessories/PID-BN94-02585B.aspx

or you may please search/ google the part number BN94-02585B to get better price info to order it. Backlight system of display panel and power supply boards are working fine as it was confirmed by unplugging connector runs between main board and power supply board. I hope these info will help. If you have any additional questions, feel free to ask. If you're satisfied, please rate me a 5-star at the top of your page.
Thank you.

Customer: replied 17 days ago.
Pin readings when power supply is NOT plugged into main board (Only even pin#'s with a wire connection is Pin#2 and Pin#30):
1 POW ON/OFF: .800V
2 H_SYNC: 4.1mV
3 STB 5.3V: 5.33V
4~6 GND: 0
7~8 13 VS: 13.07V
9~12 GND: 0
13~16 5.3V: 5.33V
17~18 GND: 0
19 13Vm: 13V
20 GND: 0
21~22 13Vm: 13V
23 INV ON/OFF: 5.25V
24 NC: N/A
25 E-PWM: 5.33V
26 GND: N/A
27 DET_5V: 5.33V
28~30 GND: 0Pin readings when power supply IS plugged into main board (Only even pin#'s with a wire connection is Pin#2 and Pin#30):
ALL (#V > 0) MEANS THAT IT CYCLES FROM THE VOLT# ***** TO PRACTICALLY 0. This cycle coincides with the transformer humming on and off.
1 POW ON/OFF: 1.5v > 0V
2 H_SYNC: 0v
3 STB 5.3V: 5.33v
4~6 GND: 0
7~8 13 VS: 13v > 0
9~12 GND: 0
13~16 5.3V: 5v > 0
17~18 GND: 0
19 13Vm: 13.1V > 0
20 GND: 0
21~22 13Vm: 13V > 0
23 INV ON/OFF: 0V
24 NC: N/A
25 E-PWM: 4058 > 0
26 GND: N/A
27 DET_5V: 2.7V > 0
28~30 GND: 0can you confirm these voltages are positive main board failure
Expert:  Shahid replied 17 days ago.

Please only check 5V and 13V DC output, if POW ON-OFF volts goes low and high repeatedly then it is main board failure. Rest of volts are control volts that changes itself as per picture settings of TV.

Rest assured, it is main board failure and replacement of identical main board will resolve the problem.

Expert:  Shahid replied 17 days ago.

Do you need any further assistance with this question?
Thanks.