Lg tv 47ln5750 led driver is problem ..

[mydang]

any people or Budm help me please !!
bought tv from people it does not work ,
detail problems is :
tv stadnd by : at P201 ---PDIM1 --3.5V OK,PDIM2--3.5V IS OK
TV ON: AT P201---N.C--12V-OK, 12V 12V-OK---24V--24V-OK

TV TURN ON see back light flash and logo half second then screen is black
used flash light to screen see manual setting......so I know main board and t-con working good,,, voltage checked at EL67 to LED+ and EL68 to LED+
it should be from 80v to 100v but no voltage when tv On,,

please help me where to check why tv turn on but no led driver voltage

[budm]

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

The LED driver Voltage at the LED connector needs to be tesetd with ref to chassis GND, each pin Voltage reading must be done when TV is turned on which mean you need to leave the meter probes in place so you can see what Voltage goes up to when TV is turned on and how low it goes down to after 5 ~ 10 seconds. You have to do that procedure for each pin of the LED connector and connector is in place.
There is also Voltage chart printed on the board.
What is DRV-ON Voltage? How many Volt do you get?

[mydang]

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

The LED driver Voltage at the LED connector needs to be tesetd with ref to chassis GND, each pin Voltage reading must be done when TV is turned on which mean you need to leave the meter probes in place so you can see what Voltage goes up to when TV is turned on and how low it goes down to after 5 ~ 10 seconds. You have to do that procedure for each pin of the LED connector and connector is in place.
There is also Voltage chart printed on the board.
What is DRV-ON Voltage? How many Volt do you get?

Tonight will check all what you said then will report later Thank Budm

[moateez]

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

check the voltage of led when it is On and Standby then Tell As Ithink is probleme Resetor
or Bad Led

[budm]

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

http://www.shopjimmy.com/lg-eay62810...pply-unit.htm#
LG EAY62810801 (EAX64905501(2.0)) Power Supply / LED Board
If you trace out the board, you will see that test points EL67, 68 are the CATHODE return of the two LED strings, they will be around 20 ~30V range. The Voltages you need to test are the two LED +, two LED - with LED connector in place.
I will not be surprised if the TV has bad LED's.
Pictures provided by shopjimmy

[neilc6]

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

LG LN series have high a failure rate of the LED backlights. Symptom is the logo flash on plug in and backlight going out once the circuitry detect overvoltage or undervoltage. I have repaired quite a few. Default settings set the backlight level to 100% on all inputs. If you don't get a logo flash, then it's time to suspect the power supply board if you are getting PS_ON and DRV_ON from the main board.

[budm]

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

Some of these series burnt out badly!
https://www.badcaps.net/forum/showth...ht=LG+47LN5790

[mydang]

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

HERE for you and people please take a look and help
Detail for you take a look WHEN TV ON
left and right led driver is 78V stable
GRD---
NC---24V
12V---12V
GRD
24—24V
GRD—
PDIM2—1.13V
PDIM1---1.13V
DVR-ON---3.22

[budm]

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

You need to follow instructions on my post #2.
You have 4 pins on that LED connector.

[mydang]

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

You need to follow instructions on my post #2.
You have 4 pins on that LED connector.

yes 4 pins at led connector 2 - and 2 +

--TV on

negative test lead to chassis , positive to pin + voltage is 78V for both

--stand by no voltage led pin at the connector

thx budm

[mydang]

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

your idea is what wrong or some backlight led burned?
Thx

[mydang]

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

one thing i do not know why ..
tv on
negative test lead to pin- ,, positive test lead to + when tv turn on i see 54v appear then disappear not even haft second
-TV Standby no volt at pin+ and -
Thx

[budm]

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

It should jump up over 100V, you did leave the probes in place before turning on the TV and keep an eye on the meter when turn on the TV? The Voltage will jump up higher than 100V real fast before going back down to 78V.
You have two boost converter circuits, one for each string so it is unlikely that BOTH of them are not working at the same time.
Then another test will be without LED connector in place and then same procedures on the two LED+ pins.

[mydang]

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

It should jump up over 100V, you did leave the probes in place before turning on the TV and keep an eye on the meter when turn on the TV? The Voltage will jump up higher than 100V real fast ( before going back down to 78V.
You have two boost converter circuits, one for each string so it is unlikely that BOTH of them are not working at the same time.
Then another test will be without LED connector in place and then same procedures on the two LED+ pins.

yes when tv turn on i see volt up 115v then drop 78v stable no change when 78V

[mydang]

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

Then another test will be without LED connector in place and then same procedures on the two LED+ pins

This test TV on show 168volt then drop 78v and stay there Thx

[budm]

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

Is this WITH or WITHOUT LED connector in place one of the two LED+ jumps up to over 100V, you have two LED+, they DO NOT have the same output Voltage so no way that both of them will jump up to be the same 115V. What are the reading for each one? We know one is 115V, what is another one?

[budm]

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

"yes when tv turn on i see volt up 115v then drop 78v stable no change when 78V" OK is this WITH LED connector in place?

[budm]

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

Then another test will be without LED connector in place and then same procedures on the two LED+ pins

This test TV on show 168volt then drop 78v and stay there Thx

You have TWO LED+ so I need the reading of both o them when TV is turn on each time, you have to do the test twice one for each LED +.

[budm]

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

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

[mydang]

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

Is this WITH or WITHOUT LED connector in place one of the two LED+ jumps up to over 100V, you have two LED+, they DO NOT have the same output Voltage so no way that both of them will jump up to be the same 115V. What are the reading for each one? We know one is 115V, what is another one?

with led connected test each time one 115v then drop 78v the other led the same 115 then dop 78v