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**budm** · 08-22-2018, 10:47 PM

Re: Lg tv 47ln5750 led driver is problem ..

At this point it's indicating that the Boost Coverter circuits are working because you are seeing over 100V on both LED+ (assuming your report is correct), so failed LED's are suspected at this point.

**mydang** · 08-22-2018, 10:48 PM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by budm View Post

I need CORRECT DATA fir each LED+ PIN! WITH and WITHOUT CONNECTOR IN PLACE and with every time you turn on the TV.

with led connect 115v then drop 78v
without led connect 168v then drop 78v

**mydang** · 08-22-2018, 10:51 PM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by budm View Post

At this point it's indicating that the Boost Coverter circuits are working because you are seeing over 100V on both LED+ (assuming your report is correct), so failed LED's are suspected at this point.

I think i will use universal le drive to test it before i open to test led backlight

Attached Files

**budm** · 08-22-2018, 10:52 PM

Re: Lg tv 47ln5750 led driver is problem ..

BTW, if you do the EXACT same procedures on the two LED - pins with connector in place, what do you get on those two pin, all done with ref to chassis GND?

**mydang** · 08-22-2018, 10:53 PM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by budm View Post

At this point it's indicating that the Boost Coverter circuits are working because you are seeing over 100V on both LED+ (assuming your report is correct), so failed LED's are suspected at this point.

Thank you i learn more thing from you

**mydang** · 08-22-2018, 10:55 PM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by budm View Post

BTW, if you do the EXACT same procedures on the two LED - pins with connector in place, what do you get on those two pin, all done with ref to chassis GND?

yes with chassis gnd connected to test lead volt meter

**budm** · 08-22-2018, 10:58 PM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by mydang View Post

I think i will use universal le drive to test it before i open to test led backlight

1) It does not show how high the Output Voltage is.
2) If you have shorted LED's on the LED string, the the good LED on the string will light up so you cannot tell if you have shorted LED or not.
3) You have to have a way to show the Total Vf (forward bias Voltage of the LED string to compare with the know good LED string).
You should invest in something like this: https://www.shopjimmy.com/sid-gj2c-l...ght-tester.htm
I have one myself.

**budm** · 08-22-2018, 10:59 PM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by mydang View Post

yes with chassis gnd connected to test lead volt meter

So you are getting 0V on both LED (-) with LED connector in place?

**chrismurphy** · 08-23-2018, 05:22 AM

Re: Lg tv 47ln5750 led driver is problem ..

You have faulty backlights

**mydang** · 08-23-2018, 07:33 AM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by budm View Post

1) It does not show how high the Output Voltage is.
2) If you have shorted LED's on the LED string, the the good LED on the string will light up so you cannot tell if you have shorted LED or not.
3) You have to have a way to show the Total Vf (forward bias Voltage of the LED string to compare with the know good LED string).
You should invest in something like this: https://www.shopjimmy.com/sid-gj2c-l...ght-tester.htm
I have one myself.

I have this one i already
*tested left led -+pin i see baclight up
*tested on the right-+pin led i donot see backlight
i think one or more leds on the right - and + pin shorted
how is your idea?
Thank B

Attached Files

**mydang** · 08-23-2018, 07:50 AM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by budm View Post

So you are getting 0V on both LED (-) with LED connector in place?

get 0v if i test - and +

**budm** · 08-23-2018, 09:32 AM

Re: Lg tv 47ln5750 led driver is problem ..

"*tested on the right-+pin led i donot see backlight
i think one or more leds on the right - and + pin shorted"
If you do not see backlights when test with tester, it means the LED string has open circuit , not shorted.
BTW, to read the Vf of the working LED strip, you just connect the DCV meter to the +/- of the LED string where you attach the LED driver.

**mydang** · 08-23-2018, 10:44 AM

Re: Lg tv 47ln5750 led driver is problem ..

If you do not see backlights when test with tester, it means the LED string has open circuit , not shorted

what do i do from here to fix open circuit led string ? Thx

**budm** · 08-23-2018, 10:58 AM

Re: Lg tv 47ln5750 led driver is problem ..

Carefully disassemble the LCD panel to get to the LED assembly, but you should get the LCD panel number first then go to shopjimmy to find the P/N of the LED strip so you can get the LED strips first before taking the panel apart.

**mydang** · 08-23-2018, 02:46 PM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by budm View Post

Carefully disassemble the LCD panel to get to the LED assembly, but you should get the LCD panel number first then go to shopjimmy to find the P/N of the LED strip so you can get the LED strips first before taking the panel apart.

how is about i can change led bulb instead of buy led string ?

**neilc6** · 08-23-2018, 03:38 PM

Re: Lg tv 47ln5750 led driver is problem ..

Originally posted by mydang View Post

how is about i can change led bulb instead of buy led string ?

https://youtu.be/YA8t8mRK5HY

https://youtu.be/EZVQKEp6jxk

Lots more youtube videos if you search including strip replacement

**budm** · 08-23-2018, 07:26 PM

Re: Lg tv 47ln5750 led driver is problem ..

http://www.shopjimmy.com/shopjimmy-l...rk-station.htm

**mydang** · 08-24-2018, 07:15 AM

Re: Lg tv 47ln5750 led driver is problem ..

replaced 2 led work great,,, Thank budm and all people " help

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