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Steven
Steven, Technician
Category: TV
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Experience:  Licensed TV repair technician in the US with over 30 experience in the US.
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Hi, I have a Samsung ps50b451b2wxxu with clicking sounds when

Customer Question

Hi,
I have a Samsung ps50b451b2wxxu with clicking sounds when it tries to turn on. I've disconnected the Y-SUS board and the clicking stops so I suspect its a short on this board. The part number is XXXXX
I would like to try and fix this board and was wondering if there was any component that was more likely to fail? Is there anything I should look out for?
Thanks
Submitted: 3 years ago.
Category: TV
Expert:  TV Tech1 replied 3 years ago.

You see the heatsinks on the Ysus board....measure the Fets and see if any are shorted.

 

 

Those may be replaceable, but the black ICs on the left edge of the board can short, killing the Fets too. You see the thicker copper traces going to those ICs? See if they are shorted to each other and you'll have an idea whether those shorted or not.

 

Customer: replied 3 years ago.

Hi thanks for your reply


 


So test the Fets first on the heatsinks starting from the top.


Do I need to remove them from the circuit it first?


 


The copper traces, Are they the ones that seem to have test points on them? there seems as though they have one above and one below the IC

Expert:  TV Tech1 replied 3 years ago.

Pull the board out for testing so you can get to the top and bottom. Fets are 3 legged with the Source and Drain being the output side, and the Gate being the input. Run a quick continuity check on the 3 legs and anything that beeps with the continuity checker is bad. Jumper gate and drain together to the Red probe....see if the black probe on the Source turns on and stays on even when you remove the jumper from the gate. When you disconnect the Drain or the Source....then it should open up again.

 

That's the general operation of how those FETS get tested.

 

Leave the Fets in the board during testing.

 

Copper traces....Power and Current are on the thick ones. The super thin ones are always signal. You check the Thick ones against the thick ones rather quickly, because if there is a short...that's the fastest way to find out. Then you hook your Red probe to each thick trace if you find a short, and slide across the thin ones to see if there is a short on the main power to data/signal lines. That's about the only way to test them.

 

Then you got to hope you can get the parts with the markings on the body of the parts. That's.....well I'm not going to call it Mission Impossible, but I am going to call it Mission Gee why did I waste all that time testing it when I can get the whole darn shooting match for this price?

 

Sorry, Mission Impossible was on last night, and I usually start researching parts first then decide if board or parts are the correct choice before troubleshooting. Parts are NOT easy to locate. Boards are easier.

 

But you should be able to check all Fets and check to see if the ICs are shorted by the time the opening theme is done --

 

http://www.youtube.com/watch?v=XAYhNHhxN0A

 

So it doesn't hurt to check them real quick then research afterwards.

Customer: replied 3 years ago.

Ok I've tested all the Fets.


 


On the top heat sink I have continuity all through them,from top to bottom.



The 2nd heat sink the 1st,3rd and 4th show no response. The 2nd Fet only has continuity from gate - drain.



The 3rd heat sink has 2 Fets both with continuity on all legs



Would this mean all the Fets have failed ???



Am I right in saying 1st leg=gate 2nd=Source 3rd=Drain


Expert:  TV Tech1 replied 3 years ago.

Yeah, anything that has continuity you have to replace. They are all supposed to read as an open circuit unless you apply voltage to the gate, and then they should have continuity until the voltage is removed from the drain and source..

 

Gate usually is the left or center leg, depending on the markings you read on the body of the Fets.

 

You need to Google those markings on the Fets next to get them. Personally, I'm not holding my breath on that, because a lot of people find they can't get just the parts for the board. I think Samsung hoards them or have some custom FET builder that doesn't post the parts online from their manufacturing facility.

 

But you never know until you try.

 

 

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