LG 55LN5310 dead

[tech2014]

Re: LG 55LN5310 dead

Did you try running the the TV board without the T-CON board connected to the main board? I cannot see how foam ball hitting the frame of the TV can knock out the TV.

Yes, no change. I did have another tv with similar issue, something struck the screen and the power died. it was a blown inrush current resistor, very strange.

[tech2014]

Re: LG 55LN5310 dead

So power supply or main board? I'm leaning towards it being the p/s.

[budm]

Re: LG 55LN5310 dead

Yes, no change. I did have another tv with similar issue, something struck the screen and the power died. it was a blown inrush current resistor, very strange.

Ah, so now we know there is at least one blown components, did you change it with the correct rating? So at this point you do have power supply problem and if you do not want to do more in-depth troubleshooting then you try another power supply board.

[Nick's Tvs]

Re: LG 55LN5310 dead

I have had a few sets come in because they were dropped and or something hit the screen really hard and somehow the tv turned off but the screen was fine miraculously! Every time it seemed to be the power supply moving close enough to the chassis that caused a short to ground. I guess I got lucky every time because there was clear sign of arcing in every situation and a small burn mark. So that gave a pretty big clue as to where to look first for bad components.
I assume you have already taken the board out of circuit since I think someone mentioned checking for cracked solder joint.

[tech2014]

Re: LG 55LN5310 dead

Does anyone have any ideas? I have tested all of the electrolytic caps, transistors, diodes, reflowed solder everywhere and still nothing. My VCC out of the SMPS controller IC jumps around. Could this cause voltages to jump around or be unstable?

[dick_barton]

Re: LG 55LN5310 dead

Go back to the beginning.
Can you isolate the power supply from the main board and use a 1K resistor from Standby Voltage to Power_On and then check the output voltages are stable.

[tech2014]

Re: LG 55LN5310 dead

Go back to the beginning.
Can you isolate the power supply from the main board and use a 1K resistor from Standby Voltage to Power_On and then check the output voltages are stable.

I did the force power up and all the voltages are unstable, on primary and secondary side

[dick_barton]

Re: LG 55LN5310 dead

Does the power supply have any radial electrolytic capacitors around the value of 1uF - 10uF, 50V or greater. I've found these often need to be changed.

[tech2014]

Re: LG 55LN5310 dead

Does the power supply have any radial electrolytic capacitors around the value of 1uF - 10uF, 50V or greater. I've found these often need to be changed.

I removed all the caps, tested ESR and capacitance and still no joy.

Is it safe to remove parts to narrow down which side of the circuit is causing the unstable voltages. I feel its on the primary side.