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Aric, Technician
Category: TV
Satisfied Customers: 44453
Experience:  15+ years in the field. Owner of AV Installation, OEM and Repair company
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Trying to diagnose a samsung LCD tv, LNT5271FX/Xaa. It won't

Customer Question

Trying to diagnose a samsung LCD tv, LNT5271FX/Xaa. It won't power on, no red standby light. I don't see any bulging capacitors, verified power cord is ok.
Submitted: 1 year ago.
Category: TV
Expert:  Aric replied 1 year ago.

Hello, Anytime you don't see a power light- the first thing you need to do is test the 5 volt pin on the power supply board to see if there is voltage in place. If there is- you have a bad Mainboard, and alternatively if there's not then you have a bad power supply board. You set your meter to DC volts, ground the black probe and test the 5V pin with the red probe. It is very unlikely you will ever see a burn mark on any of these boards.

Expert:  Aric replied 1 year ago.

If you're missing the 5 volt line, then you will purchase the power board at the link below and swap it to fix the issue:

Expert:  Aric replied 1 year ago.

Alternatively if you have the 5 volts present- with NO power light indicator, then your Mainboard is faulty and requires replacement. It can also be sourced from the following link:

If you need further assistance let me know. Please do not forget to click a POSITIVE RATING before you go- as it's how I am credited for my work. You can follow up at any time, at no additional cost.

Customer: replied 1 year ago.
Thanks for the info. I found no voltage at the 5v pin on the power board. I have ordered a power board. Once I receive it and verify it is fixed, I will provide the feedback so you get compensated.
Expert:  Aric replied 1 year ago.

That sounds good.

Customer: replied 1 year ago.
I got the power board today. It behaves exactly the same way.Perhaps I should've asked this sooner....which connector should I be looking for 5VDC on? I see 2 connectors in the corner near the model number. Once has. 5 pins, the other has 24 pins. I've checked the pins 13-16 on the 24 pin connector and pin 5 on the 5 pin connector. I don't have 5VDC on any of those pins.
Expert:  Aric replied 1 year ago.

The 5 volts would be labeled on the power board where the connector is that provides this voltage. Can you see the legends with the voltages stamped near them?

Customer: replied 1 year ago.
I've attached a picture of the two connectors I mentioned. The picture also captures the legends that describe those two connectors.
Should I have 5v on pins 13-16 of the 24 pin connector? Should I have 5v on pin 5 of the smaller connector?
Expert:  Aric replied 1 year ago.

Let's try this a different way- do you have 5 volts on ANY single pin on any of the connectors at all?

Customer: replied 1 year ago.
I have 5.2V on pin 4 of the 24 pin connector. According to the pin out printed on the board, that should be ground.
Expert:  Aric replied 1 year ago.

So long as there is 5.2 volts present- then we know you have standby, and the other component that is responsible for powering the power board up is the mainboard (the board with the AV jacks on it), So you would need to replace the mainboard to fix this problem.

Customer: replied 1 year ago.
Main board replaced. TV powered on, but will not turn off by means of the remote control, the touch switch on the bottom of the frame, or the push buttons on the side of the frame.
It's basically stuck on one input (HDMI3) and volume level.
Expert:  Aric replied 1 year ago.

Yes, the quality of the 3D when it's turned off is identical to a non 3D.

Customer: replied 1 year ago.
Did you answer someone else's question here? Your response makes no sense for my situation.
Expert:  Aric replied 1 year ago.

No, the site has a new format and the question I answered was sent to you by accident on their end. The Mainboard being replaced with a properly working Mainboard would not render the Source or Volume as being stuck- disconnect and reconnect your button board to the mainboard and if that does not work- then they sent you a faulty mainboard and you need to send it back and get another.