I have an LG LED tv here that has standby voltage, and upon pressing the power button the LEDs blink on and off every few seconds. Even when the LEDs are off the display can still vaguely be seen. The voltage at the LED connector fluctuates
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LB5550 Backlight blinks
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Re: LB5550 Backlight blinks
We need to see the pictures of the whole back side of the TV showing all the boards.
We also need to see the Voltage readings of all the pin at the connector of the power supply board that goes to the main board, also the Voltage readings of all the pins of the LED connector.
You MUST put down the pin name and follow by the Voltage reading for each pin, giving just the Voltage reading without the pin name will be useless.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: LB5550 Backlight blinks
LED connector has voltage fluctuating as stated before,
itsjust 4 pin LED + - + -
main board connector is as follows
GND - 0V GND - 0V
12V - 12V NC - 0V
12V - 12V 12V - 12V
GND - 0V GND - 0V
24V - 24V 24V - 24V
GND - 0V P-DIM2 - 1.2V
3.5V - 3.5V 3.5V - 3.5V
3.5V - 3.5V P-Dim1 - 1.2V
PWR-ON - 3.3V DRV-ON - 3.3V
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Re: LB5550 Backlight blinks
Originally posted by XpressComputers View PostLED connector has voltage fluctuating as stated before,
itsjust 4 pin LED + - + -Originally posted by XpressComputers View Post
main board connector is as follows
GND - 0V GND - 0V
12V - 12V NC - 0V
12V - 12V 12V - 12V
GND - 0V GND - 0V
24V - 24V 24V - 24V
GND - 0V P-DIM2 - 1.2V
3.5V - 3.5V 3.5V - 3.5V
3.5V - 3.5V P-Dim1 - 1.2V
PWR-ON - 3.3V DRV-ON - 3.3V
What is the power supply board P/N?Last edited by budm; 06-11-2018, 12:54 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: LB5550 Backlight blinks
TV full model number is 55LB5500?
What is the LCD panel model number?
Shop jimmy version 1.0 Power supply board: LG EAY63072101 Power Supply / LED Board, http://www.shopjimmy.com/lg-eay63072...-led-board.htm.
Can we see straight shot pictures of the whole top and the bottom side of your? I cannot use the pictures from shopjimmy because PCB version is 1.0, your board is 2.1.Last edited by budm; 06-11-2018, 01:58 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: LB5550 Backlight blinks
LCD panel model number?
I need to verify the LED strips being used, so far all I know that it has two LED strings with two driver circuits with two different Voltages outputs (145V and 218V as printed on the board Version 1 and also on your board).
So based on your readings, they do not look right and point o bad LEDs.Last edited by budm; 06-11-2018, 02:01 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: LB5550 Backlight blinks
Model LC550DUE (FG) (A6).
I will look up the spec. sheet to get the LED info.
I still need the high res picture of the bottom side of the board to verify the LED driver circuits and how the LEDs are connected.
BTW, do you LED tester? Something similar to this: http://www.shopjimmy.com/sid-gj2c-le...ght-tester.htmNever stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: LB5550 Backlight blinks
I am checking to make sure that there are two LED strings driven by two LED driver circuits, which they are.
So what does the LED tester meter show for each string of the LED?
The LED string connected to pin 3 and 4 look to be where the problem is.Last edited by budm; 06-12-2018, 09:22 AM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: LB5550 Backlight blinks
You have TWO LED + and TWO LED -, as you look at the bottom side, then you can easily see how each LED string is connected to the driver circuits.
See the two surface mounted MOSFETs close to the LED connector? Each LED - is connected to the Drain of the MOSFET, the Source is connected to the current sensing resistor and then to GND.
There are two Voltage boost converter circuits for each LED string that feed each LED +.
Get the P/N of that SMD IC close to the MOSFET to get the spec. sheet then you will see how it works.
The LED string that show 200V withe tester which only putting out around 20 ~ 30mA, at 400mA the Vf of the LED string will be much higher than 200V, LED power supply for that string is rated at 218V.Last edited by budm; 06-12-2018, 09:54 AM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: LB5550 Backlight blinks
https://www.badcaps.net/forum/attach...1&d=1528819719
I cannot read the p/n on the top line.
BD???????Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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