LG 47LG5000 Blown Resistor

[Klinux]

I picked this 47" LG LCD TV model 47LG5000 up recently, it wont power on, the red power led blinks then powers down. I've removed the power board checked the caps nothing obvious there but as you can see from the pics a resistor in the bottom left of the PSU board has blown. I don't know what the history of the TV was ie it's behaviour before it blew. I'm having problems identifying the resistor, I'm also interested in the more expert opinion on why this resistor has blown.

The caps look ok but that doesn't mean there not bad, I've fixed a few LCD's in the past that suffered from the usual bad caps, but having problems identifying this resistor.

I'd appreciate any help and advice.

[tom66]

Re: LG 47LG5000 Blown Resistor

The resistor is a safety class-Y type resistor. If it failed, there was a significant (>500V) over-voltage between live/earth or neutral/earth, i.e. surge damage. Its failure though will not stop the power supply from working, so there is likely another fault. Value uncritical - from 4.7 Megohm to 10 Megohm safety rated.

[Klinux]

Re: LG 47LG5000 Blown Resistor

Thanks Tom for the info, looking at the location it was my assumption that it had suffered from a surge. When you switch the set on the red led blinks then goes off, I figured the TV was powering off because it detects a fault namely the resistor. I wouldn't be surprised if the Tv has received a surge from the power supply, I used to live in the town where I picked it up, very old houses used to sufferer from blown gear all the time myself.

[tom66]

Re: LG 47LG5000 Blown Resistor

There is no such fault detection circuit. Detecting the possible failure of every resistor on the power board would be extremely costly. Something else on the power supply has failed.

[Klinux]

Re: LG 47LG5000 Blown Resistor

That wasn't what I was implying but thanks anyway

[Klinux]

Re: LG 47LG5000 Blown Resistor

I've tested all the power outputs from the powerboard and also replaced the blown resistor. All the voltages are present. Their is power going to the mainland I can also see the optical output is shining red. I'm starting to wonder if the fault is on the mainboard.

[tom66]

Re: LG 47LG5000 Blown Resistor

That would be my guess. You can also test the backlight if you want by jumpering BL-ON to 5V with a 100 to 470 ohm resistor.