LG TV 55LF 55LB NC55 No Backlight - LED Voltage Test - Troubleshoot TV LEDs & Power Supply
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- Опубликовано: 28 авг 2024
- How to test Voltages to Determine No Backlight Symptoms
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LG TV Models:
55LF6000-UB AUSCLOR
55LF6000-UB BUSCLOR
55LF6090-UB
55LF6000-UB BUSYLJR
55LB5900-UV BUSWLJR
55LF6000-UB BUSYLJR
55LB5900-UV BUSDLJR
55LB5900-UV BUSCLJR
55LF6000-UB BUSCLJR
55LF6100-UA
55LY340C-UA BUSDLJR
Try all repairs and troubleshooting at your own risk.
In this video, we will show how to test voltages to know if the problem of no backlights is being caused by the power supply board or the LEDs.
We will show multiple scenarios, so you should be sure you have the proper training and equipment to test voltages on a live TV, with power going to it.
Try all repairs and troubleshooting at your own risk, as this can be dangerous.
The power supply connection here, runs from the power supply to the LEDs. This will be where our test points are.
There are multiple test points labeled as LED+.
Before testing you will want to plug in the TV and turn it on. Everytime we test a point, do the following. Place your black probe on a ground and then place the red probe on a test point.
The first point we will test is this LED +.
I am getting a reading of 215 volts, which is normal.
On the next point I get a reading of 145 volts, which is also normal.
Since there are an odd number of LED strips in the TV, one point provides power to three strips and the other to just two strips, so the voltages are different.
With both of these voltages showing the correct voltages, it shows that both the power supply and LED strips are working correctly.
If I test the points and get voltages that are closer to zero, we will need to continue troubleshooting to see if the problem is the power supply board or the LEDs.
With readings at zero, unplug the power from the TV, after unplugging disconnect the cable.
Plug the TV in and power it on, and then test the same points again, but on the other side of the connections, since the cable is unplugged.
When testing these points, if we get voltages that are close to 270, that is showing that the power supply is functioning properly and there is most likely a problem with the LED strips, that is causing the voltage drops when the cable is connected. The LED strips should be replaced.
When testing these points, if we get voltages that are close to zero, that would show that there is most likely a problem with the power supply and it should be replaced.
We have links in the cards and description for this video to help continue your repair. Click those video links to learn how to replace a board, and replace LED strips.
The voltages in this video are specific to this TV, but the general process of the troubleshooting method we have shown should apply to other TVs with similar symptoms.
TV Repair Made Easy™
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Thank you, this video was very helpfull for determining if my LEDs or PS was broken on my 55UF6450. Great content!
I have an LG 55LN5310. The voltage readings are 91 V on both LED+ terminals when the connector is plugged in and the voltage is the same when the connector is unplugged. Where do I find what the voltage should be for this tv? What do these results signify? Thanks.
Hi, did you find out?
I have no Voltage 0V for the LED light , and Replaced the Power board based on this advice , and its still 0V . The TV works , there is Sound and Picture just no Light .
Did you figure out what the problem is? I'm getting 0V for LED1+ and LED2+ on both sides of the connection. Seems like Power Supply, but your comment makes me wonder. Thanks.
@@nathanp39 Yes i did , the Power Supply has a Sensing function and if it doesn't see the correct load it cuts down power . Which means it was LED strips gone bad and power supply was in protect mode . That is why when i changed the PSU nothing changed , since it was working in the first place .
Just showing that the You Tube Videos are most times just People running their mouth and should not be considered for advice .
So check your board Transistors , if you dont find bad Caps , Transistors or something not working , then it works and its the LED strips gone bad .
This is pain in the ass because changing 55inch LED strip is not easy . Taking apart the screen can lead to damage , but good thing is that it is usually 1 or 2 LED , and you can change them individually on cheap .
But you need time and space , and effort to disassemble the screen .
Hey I was just given a lg 55 uh6090 and the screen is half darkened. So looking at the screen the left half is dark. Is that a bad power supply board?
Have you ever seen all the back light strips go bad half way across each one? I don't even understand how the powerboard would be the issue. Half the lights in each strip work lol I haven't seen this one yet
Excelent video ! I have one question. I got a 55 inch tv where one of the leads stopped working. Can I bypass that led , removing the old led and wiring a bridge JUST to test if they all get LIT correctly. NOT as a final solution, just as a way to check if the other strips are working ?
Yes, you can only if all the LEDs are in series. The PSU will readjust the voltage to limit the current in the rest of tht LED's. But there are parallel designs on some TVs, and if one LED fail from a strip, the current will drop significantly and the PSU will keep the output low to protect the rest of the strips. In this case bypassing one LED the PSU will put the maximum power out and will burn the rest of LEDs. This is a bad design adopted for the new TVs. That protection for the rest of the strips is not so good, most of the time the PSU will burn all LEDs if one fails.
Good day... Is it posible if the tcon board was damaged the backlight will stop working..?
when testing the power supply board. you didn't explain where to set my volt meter. should that be important. or could I just set the volt meter anywhere? thanks
My tv when plugged in the standy by light will blink once about every 4 seconds but if I press the power button to turn it on the standby light goes off
Hello
I chcecked my TV LG - on LED+ i have 230V but on LED- i have 130 v - it's normal??
Best Regards
Have an LG 55LB6300-UQ.BUSWLJR. Ordered LED strips from you and replaced them. Tested the LED strips pulled and found 2 with burn marks and 1 open LED. The TV still flickers. Tested PS board with LEDs disconnected and the voltage pulses on and off. My question is before ordering the PS board from you, is there a possibility of the Main board being defective as well. PS board is EAY63072101.
What voltage and wattagefor each led? I go replace them myselfs, I have proper solder gear.
No I toasted the power light the power going to the LEDs and it's only showing zero two volts so what would actually be the issue
I have LG 49UF6800 with Menu, Home command working fine with sound and shows clips of RUclips small fine. The problem is when you play it for full screen, you get Grey screen withh faded vertical lines with sound OK. What's wrong? Pls advise?
Backlight not working on LG 42LB5600-UZ with EAX65423701 power supply. Has video showing in flashlight test. LED+ test point shows 106 VDC with the backlight connected or disconnected. No voltage on the LED- connection and no voltage between LED+ and LED-. Label on power supply lists output at 208V. Do I have a power supply problem or and LED strip problem? If this is an LED strip is the problem, did it damage the power supply?
I have a Blackstar TV bs32 it's a 32 inch is has no picture no sound but the poet can turn on there is just the standby light and I can't turn it on is it the backlight or the motherboard sometimes I see it comes on bright and the picture is blinking
Hi , where or how can I find find a diagram for LGP55LIU-16CH2 , I HAVE PROBLEM I NEED IT ,THANKS
Thank you so much I will try this.
I have an 65 UK6100Y lg tv, the led is working But in dim lightning, the image is super dark, i test voltage without the led plug and it show 270v
When i test with the plug it show 260v
In this tv ther is only 2 wiers led+ and led-
What can be the problem?
Hi there, is it possible that only 1 strip is bad and still we get voltage from strip side? in my case one of r1 strip is bad but can see voltage from both power board and strip side. can you/ someone please clarify? Thanks
After changing me led strip to new strip
The new strip gets very hot compare to the old one
Is my led strip is wrong
Okay so my LG only has 1 LED+ and 1 LED-.
My TV's fault is that the backlight doesn't come on most times, MOST TIMES, but once in a blue moon it does, but not for good, turn it off once and it's broke again. Or even changing the HDMI channels can do that too. I guess it's anywhere where the Backlights go off, there's a chance they wont come back on again.
Like 99% chance.
I followed the diagnostics shown here, when the screen backlight is working (a rare opportunity now) I get roughly 210V plugged in but I couldn't get a test for when plugged out of the power supply board as it never came back on after switching off, but I've also tested it when the backlight isn't working and get roughly 107V plugged in and plugged out...
Note, I haven't taken apart the front to look at the LED strips but counting the ribs from the back make it look like it's probably 4 lines of LED strip.
Also, the TV is 8 years old.
So I'm not sure but I presumed each line of LED strip must require about 50V each and for some reason the power supply is faulty.
Does that seem to be the case??
Hi, I have a Sharp LC-50LB371U Manufacture date 6/2015. I have no picture, no audio (however I hear a tone when powering off TV), no backlights. I can see the menu when doing the flash light test. Voltage tests on the main power board on the LED connector are as follows. I get 65.74 VDC on LED 1 and LED 2. When I disconnect the connector plug I get the same voltages on the opposite side of the pins. Please advise.
Did you sort it i am getting the same
Yesterday my LG 42LB5500 went black screen. I took the light of my cellphone and light up the screen and I saw that there was image but without light. There was audio and also the red power off led worked fine. Today with the multimeter I did a voltage test in the led power supply part and I had 100V with the led cable and without it and with the tv on. Right now I dont know if the power supply is the problem because it says that it should be 280v for output and I had 100v. Can someone help me?
Hi I have this monitor circuit board (F)QCCB0DL0110000 S/N: 33E71690LM0027 M3C201 I wanted to disable the sleep mode so I can use the monitor back light as normal light. I don't know which on I need to bypass in circuit. If you can help me will be great.
Good.nice sir
what setting should the mulimeter be on? i have never used one just purchased a $20 one to test this i have the exact model tv u are fixing please advise
your vidoes are awesome btw thanks
How do you figure out what the proper voltages are for your specific TV? I have a LG 65UK6300PUE.
Led strips - 3v per led so 10 led per strip = 30v for example
I had 7 leds burned out of my TV. I replaced them and tested them individually before powering on tv. After I replaced them all I connected the power boards everything except the display itself. When I power it on they all come on and blink except one that doesn't go completely off it just flashes and gets dim. This is one in the first series. Is there a reason this is happening? I replaced it and still does it I also replaced the other one in that series that I replaced earlier. I really need some help here please.
I found the problem. I had an 8th led that was bad but still lit up just not as bright as the others. I put on sun glasses and watched after replacing the 2 in that series twice and found one in a different series that didn't seem to get as bright as the others so I replaced that one then plugged it in again and they all lit up evenly and stayed lit. Now the TV works beautifully and I'm very pleased. If anyone ever has this issue hopefully this will help them. It's very hard to find because the lights are so bright it blinds you and makes it hard to see one light in the middle lol.
Sir lg 49 inch led tv red light blink 3 time no power on plz help
Philips TVs are different. LED strips are connected in parallel. If one LED fails, the PSU will kill all other LEDs because is a fixed current PSU and the current is calculated for 5 LED strips with a voltage at maximum 55v.
I've got fooled by injecting current from an external LED PSU with a greater voltage and lower current because the voltage drop across the failed LEDs have been increased to about 10v. The panel got lighted with this external PSU and had no light with original undocumented Philips PSU wich i thought is faulty. Finally after digging the internet found out that the LEDs strips are connected in parallel, than i have opened the panel and found that are faulty LEDs.
Now testing the original PSU once again with a power resistor of 50ohm on output i still get 55v with 1.1A. This looks like a lot of power to me and I don't have a lower resistance resistor to test for the maximum current the PSU delivers and i can't find any info about the LEDs strips and the maximum current per strip. There are 5x12 series LEDs, does anyone know the current for a LED strip? I am afraid not to fry the new LEDs.
I have a 55 inch LG LED TV (model is LG LN54M550060V12). I performed the flash light test and I can notice image in the background and the audio is working fine. So, i proceeded with testing the power supply board s instructed. I see that the voltage on both the LED+ nodes is around 80. Even if I disconnect the LED power supply connection and check the voltage, I see the same reading. Is that normal? Per the videos posted, I see that the voltage when the LED power supply cable is connected is lower than when it's detached. So, do you think it's an issue with the power board (or) LED backlights?
I have the 55LN5710 LG with the same problem (LG logo & flash, black screen, sound working) and I tested the voltages and got the same result as you. Did you solve it?
Thank you very much for your help! I'm going to open my TV and change the defective LED strips
@Brenton Tripley Thanks, problem solved. :-)
Yeah, keep the solution to yourself. @@MrNedzedster
unable to find this testing point on my hitachi 55 inch tv. does anyone know what it’s marked?
The 'Testing point' could be anywhere. This is just the most likely area of there being a problem.
Hi, Can anyone please tell me where can I order a replacement power supply board for LG 55LF650T? Please help.
search ebay for the part's model
Hey all my leds are working but when they flash I’m hearing a click from the power board. Anyone have any ideas?
Hi, thanks for the informative video. My LG TV (50lb6300) starts blinking when I power it on from yesterday. It blinks for every second and when I play something, the audio is good and video is running but keeps blinking. So I tried the following
1. Disconnected the ribbon cable to t-con and powered on the tv, still seeing the blinking LEDs - so suspected LED issue.
2. Measured the output voltage in all the pins from power supply board to mother board. All are same as specified in the PCB.
2. Measured the voltage at the LED output pins in the power supply board:
- With led cable connected,
a. middle LED+ pin voltage varies from 135v - 147v
b. edge LED+ pin voltage varies from 135v - 140v
- With led cable disconnected,
a. middle LED+ pin voltage varies from 128v - 147v
b. edge LED+ pin voltage varies from 140v - 160v
Can you please let me know what's the problem
My tv clicks twice to go on now it clicks 3 times and doesn't turn on Help pls
Why we put the negative pole of the multimeter there and don't put it on the led-
Damn it to hell! I swear my luck is #*&@! I took pictures of led wiring then took strips off so I could replace them. Unfortunately I got very busy and had to work really long hours and weekends until now but guess what my damn phone broke and apparently didn't back up all the pictures so I watch this video hoping their would be a quick picture of the led wiring but of course not! It shows the led strips only for a few seconds but after the freaking wires have been removed! Why I don't know but it's so freaking aggravating!
No backlight after 30 minutes
Model Philips 55inc led
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Y not. In Tamil
my power supply is 115 volts . when i test my led output i get 57v
What if the voltage is over 400. Seriously it's over 400.
Mine is 410! Wtf?