LG 47inch TV turns on but backlight shuts off quickly

[Lithium_Tonic]

Hey Everyone,

I have an LG 47ls4500 and had an issue come up in the last couple days.

When I turn it on it appears perfect. Nice and bright normal good picture but then after about 3-4 seconds the backlight just turns off. I can see that the screen has video on it but it's to dim to make anything out. The TV operates perfectly normal just no backlight. I tried turning it off and back on several times and it consistently does the same exact thing.

I know there is three boards in the back. The power supply/LED board (which I checked for bad caps and they all looked fine), the main board and the T-Con board.

From what I've read this can likely be fixed relatively cheap but my biggest concern is which board is the actual problem.

I appreciate any help on this.

Thanks,

Steve

[mann935]

Re: LG 47inch TV turns on but backlight shuts off quickly

This is a led tv and by the details you have given it seems you have a pic. but it is dim,if that is the case ,on menu pressing is it ok?

[Lithium_Tonic]

Re: LG 47inch TV turns on but backlight shuts off quickly

This is a led tv and by the details you have given it seems you have a pic. but it is dim,if that is the case ,on menu pressing is it ok?

Hey thanks for the response. When I press the menu button I can see that the menu comes up, however the backlight is still off. If I shine a flash light at it I can see that there is a picture.

[budm]

Re: LG 47inch TV turns on but backlight shuts off quickly

How about posting good clear and well focused pictures of the back of the TV and also straight shot pictures of each boards?

[geminidpr]

Re: LG 47inch TV turns on but backlight shuts off quickly

Hi Guys. I'm having the exact same problem with the exact same model (LG 47LS4500). It turns on and looks and sounds great for just a few seconds then the backlight goes off but sound stays on. I put a flashlight to it and I can see video so definitely a backlight problem.

The power supply has an LED that is blinking 4 times. I believe this is an error code but I don't know the error codes for this model. Does anyone have the error codes for this TV?

Thanx.

[budm]

Re: LG 47inch TV turns on but backlight shuts off quickly

We need to find out if the BL-ON (DRV-ON) signal to keep the backlights on is still present when the backlights drop out, so you need to check DCV on connector P201 DRV-ON to see if it has >2.5VDC at that pin when TV is on and when the backlights drops out.
This TV has 12 LED strings controlled by 12 circuits. You will have to check the DCV of each pin of the LED connectors P202, P203. You MUST provide the pin names and follow by the DCV reading for EACH pin.
Lg eay62512701 (eax64310401).
Pictures provided by shopjimmy.

[Diah]

Re: LG 47inch TV turns on but backlight shuts off quickly

Hi Guys. I'm having the exact same problem with the exact same model (LG 47LS4500). It turns on and looks and sounds great for just a few seconds then the backlight goes off but sound stays on. I put a flashlight to it and I can see video so definitely a backlight problem.

The power supply has an LED that is blinking 4 times. I believe this is an error code but I don't know the error codes for this model. Does anyone have the error codes for this TV?

Thanx.

this PWB even if you disconnect the LED plugs the green indicator will turn on flashing . also its possible you have bad soldering ... if there no bad soldering then you have one shorted edge LED

[geminidpr]

Re: LG 47inch TV turns on but backlight shuts off quickly

Drv-on is at 3.3v when BL comes on and stays exactly the same when BL goes off.

LED + (P210) is at 36v when power is switched on and when BL comes on it goes to 56v then drops slightly to 53v when BL goes off.

Connectors P201 and P202 voltages are all at 7v when BL is on but jumps to 18-19v when the BL goes off.

[geminidpr]

Re: LG 47inch TV turns on but backlight shuts off quickly

this PWB even if you disconnect the LED plugs the green indicator will turn on flashing . also its possible you have bad soldering ... if there no bad soldering then you have one shorted edge LED

Thanx Diah. I resoldered any suspicious connections and replaced main filter and C263 (100uf at 150 volts) and still the same so maybe it is LED array.