Hi, it looks like there is blown up resistor on the led tv power board. I want to replace the whole board but wonder what might have caused the damage (shown on the pic). How did it happened. Is it internal TV problem (5 years old tv) or rather external issue, power supply? Is it worth repairing it and is there a way to prevent similar damage in the future.

 

A schematic for the set would be a help in diagnosing what the cause could have been.
There are some sites that offer schematics for some makes.
Max.

 

There's a decent probability that one of the electrolytic capacitors has failed. You could mess around testing and diagnosing them all but the reality is that it's faster to just replace them. They go bad over time and the ones under stress (a lot of AC current) will eventually go bad even if they haven't yet, so replacing them is not a loss, and might fix it.

I used to think this recommendation was nutty but I've become a believer.

 

It looks like the resistor is on the primary side of the switch mode power supply. The IC next to it is the switch mode controller IC. (Link to datasheet) I suggest tracing out the schematic of that part of the board to see what that resistor does. There is an example schematic on the data sheet so it should be possible to identify it's function. I think the fault is internal to the power supply rather than excessive load on one of it's outputs but I would do some investigation to confirm or disprove that susspicion.

Les.

 

Yes, that resistor is likely connected to that IC's MOSFET source as the current sense resistor. It happens that such MOSFETs go short circuit and that would destroy that resistor. Usually when such things happen in switch mode power supplies that other components will be damaged. What makes these supplies difficult to repair, even for those experienced in such things and having the schematic, is that if fail to find one of the damaged components then it will go bang again when powered up.

 

Yes, that resistor is likely connected to that IC's MOSFET source as the current sense resistor.... go bang again when powered up.

Thank you for your answer. So would you advise to replace the power board only? Or mother board might be affected too (no visible damage on other boards)

 

The damage is probably restricted to the power board but there is no guarantee of that without experience of this board.

 

It's a Smpsu chip A6052m, note Pin6 is missing deliberately...
The resistor will be connected to pin 1 current sense.