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No power, No power led

Philips 55PUS7272


Hey, today a 55 inch uhd tv rolled in my door and i proceeded with some diagnostics in my attempt to try to learn this kind of stuff. i’m very new but i want to learn hehe.

So, to my tests and findings.

I plugged in the power, tried powering on with controller and button on the tv. Nothing.

I opened it up, unplugged the power cable to the motherboard from the PSU to see if the backlight would turn on. Nothing.

I then checked the voltages of said cable compared with the stamped pinout on the board and everything is wrong. Every 5v shows 3.6v and every 12v shows 3.4v.

Now, i can replace the PSU, but are my findings a definitive PSU board issue? Also how do i go about finding the exact culprit?

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@sikator it always helps if you let people know where you measured, what you measure and when you measured. All of that makes a difference. We would need to know which connector, what point on the connector and was the TV on or off when you measured. Did you still have the power board and main board disconnected? All those things are important when diagnosing. Also, I do not believe that Philipps TV's turn the backlight on when your disconnected the main board from the power board.

Yes, from what you are describing, this could be a power board issue. Measure the board correctly and see what voltages you get.

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Hi @sikator ,

Here’s a link to the service manual that may help.

I haven’t checked it out but usually service manuals have schematic diagrams that should help you to find out why there is incorrect voltages being supplied.

Hopefully this is of some help.

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Wow im new to tv repairs. didn't know this stuff was available!

Well, i don't really know what to do from here :S

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@sikator

You would need to be able to read schematic diagrams to find out where the power was coming from i.e. either start at the AC input and then work your way through the circuit or start from one of the points you measured and work back through the circuit to find the path that it receives its power from and then work out why it isn't getting what it is supposed to e.g. faulty component or perhaps the power is being shunted perhaps etc

You would have to know electronic components and their symbols and what they mean i.e. resistor, diode, power transistor, inductor etc and how they work differently.

Board level fault finding is not as simple as some people think ;-)

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preben frank sera éternellement reconnaissant.
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