Help lg 47lw5600 backlight going out

[mattstolte]

got this set when I power on backlight will come on then after a few sec. backlight shuts off but power is still on. I have all proper voltages but the last 24v where is says pwr on is only 3.5 so im not sure if its suppose to be 24 or not?

[budm]

Re: Help lg 47lw5600 backlight going out

Please upload the pictures of the whole back side of the TVto show all the board and pictures of the whole power supply board top and bottom side.

[budm]

Re: Help lg 47lw5600 backlight going out

'pwr on is only 3.5; That is the same as PS-ON, it is the control signal form the main board to turn on the rest of the power supplies, so 3.5VDC on the PWR-ON is correct.
P201 is 24 pins connector.

[budm]

Re: Help lg 47lw5600 backlight going out

Is this your power supply-LED driver board?
http://www.shopjimmy.com/lg-eay62169...upply-unit.htm

LG EAY62169801 (EAX62865401/8) Power Supply 47LV5500 47LV5400 42LW5300
16 LED strings!

[mattstolte]

Re: Help lg 47lw5600 backlight going out

yes and I just checked 1 of the pins going to the leds, starts up at 65v drops down to 35 when shuts off

[budm]

Re: Help lg 47lw5600 backlight going out

So the LED + pins of LED connectors P202, P203 show same reading of 65V?
It sounds like it goes into protection shutdown.

[mattstolte]

Re: Help lg 47lw5600 backlight going out

bud all the + start at 65v when the backlight is on then after 3 secs the backlight shuts off and the + will all read 35v

[johnboy1313]

Re: Help lg 47lw5600 backlight going out

Have you checked for faulty LEDs?

[budm]

Re: Help lg 47lw5600 backlight going out

OK, using Chassis as the GND ref for the meter.
Take the DCV reading of all LED strings GND return, there are 16 GND returns, they are test points EL62~EL77, you will have red probe connected to those test points start with EL62, you will have the cycle the TV ON 16 times, we need to find out if one of the string has open circuit or not so correct measurement is very important.

[mattstolte]

Re: Help lg 47lw5600 backlight going out

They all go up to 10v when there on then once backlight goes off they go down
el62-el77
1.8
1.8
6.2
7.8
4.7
3.1
3.5
4.9
5.2
4.7
6.2
4.9
3.9
2.0
2.6
2.3

[mattstolte]

Re: Help lg 47lw5600 backlight going out

Budm would we say bad led?

[budm]

Re: Help lg 47lw5600 backlight going out

Budm would we say bad led?

Yes, I expect the readings to be really close to each other.

[mattstolte]

Re: Help lg 47lw5600 backlight going out

I have not had many led sets come in my shop. Where the backlight flash with bad led. Usually the bad led I have had come in usually screen does not light up at all. But all other voltages are present so I guess it would have to be leds?

[mattstolte]

Re: Help lg 47lw5600 backlight going out

I also wanna thank you. You and tom have been the lifesavers of this forum. Without you two I dont know how else would be here.

[budm]

Re: Help lg 47lw5600 backlight going out

The one that does not come on at all are the one that has all the LEDs connected in series like a Christmas light, one goes open circuit then the whole string will not light up, this one has 16 LED strings and one circuit for each string, so if one string goes out the other will still light up but the protection circuit will kick in.

[mattstolte]

Re: Help lg 47lw5600 backlight going out

Is there anyway to bypass the protection circuit and make it run like it is now? Cause when picture comes up it looks fine. Not lighter anyewherw on picture

[budm]

Re: Help lg 47lw5600 backlight going out

There are two SMD ICs on the bottom side of the board close to those test points, I believe they are for the LED driver circuits. You will have to get the spec sheet to find out how it works and how the protection circuit functions.
By the way, is there a cable between T-CON and the power supply board?
Can we see the pictures of the whole back side of the TV?

[mattstolte]

Re: Help lg 47lw5600 backlight going out



I will get pics of the bottom of power supply Tmrw thanks