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The LG 60LM6450 is a 60-inch LED television released in 2012. It supports 3D video with glasses at a resolution of 1920x1080 pixels.

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Why is my TV not displaying? Three LED blinks.

Hello Community,

I have an LG from a year ago and today, it randomly turned off and the screened stayed black with the back-lights on. After diagnosing and researching online, it was either a bad inverter or capacitor, which are both located in the power supply board so I just decided to replace the t-con board, the main board, and the power supply board to be safe. It doesn’t cost as much as a whole new tv. They were purchased off tvpartstoday and the condition was new. After installing all three brand new boards, the LED still blinked three times and the screen was not displaying the LG logo.

TV with new boards displays:

standby: 1.9V

Operating voltage: 13.1V

When I unplug the back-lights the voltage measurements do not change.

When measuring the 4 pins on the LED pins I get:

LED2 - : 3.6

LED2 +: 132V

LED1-: 5V

LED1 +: 198V

The TV’s back-light are mainly shinning on the left and right side of the tv, the middle is pretty much dark. I’m not sure if that can help solve the issue, could it be s trip is bad?

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Hi @ericlg

I’m assuming that the LED voltage measurements are between the pins and Earth, is this correct?

Did you try measuring between LED1+ & LED1- and LED 2+ and LED 2- to see what it measures?

I would check that all the strips are working OK. You may have to access the strips and check that the power is getting to or through the middle LED strips.

Try using a TV backlight tester to make it easier. That way you won’t have to have power on the TV to check the LEDs and you won’t have to disassemble the TV to get to the LEDs if they all work when a tester is connected to power them. If they all work with the tester it is back in the power board. If they don’t it’s in the LED array somewhere

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Hello Jayeff,

You are correct, those were measurements from LED to ground. I will measure LED to LED later today. What should I expect?

That is a neat idea, I have one of those handy due to a different project, I hadn't thought about that. Could a bad LED really cause the whole LG TV to not display and cause the three blinks?

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@ericlg

One bad LED on a strip can turn off a whole strip of LEDs because they are connected in series connection on the strip.

Not sure with LG but I know that with some the power board is "monitored" as to how much current /voltage is being supplied to various circuits and if not correct the TV is shutdown to safeguard the rest of the TV with the resultant error code being displayed. It would be nice to know what they mean for a lot of TV as Samsung, Toshiba, Sharp et al don't say whereas others may do if at all but then only for their older models that are no longer supported by them.

With the voltage measurements i don't know what to expect but what I would expect is that they both should be the same if both circuits were OK. usually power board design doesn't provide two the same power supply circuits i.e. two LED circuits and then to supply two very different voltages. It is easier to make them both identical. I'm thinking that the 132V DC may be OK or close to it because the figure I had in mind was in the range 100-150V DC but this is a total guess as I'm really not sure. All I know is the higher the voltage usually means less current is flowing due to an open circuit somewhere and the voltage goes up at the power board because it is not being used at the load. having no LEDs in the middle seems to confirm this for me anyway.

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Hello Jayeff!

I finally got around to working on the TV again since work has slowed down a bit.

So, I decided to disassemble the TV and physically inspect the LEDs. They look perfectly okay and even took a 12v source and tested each individual LED and they light up really brightly. I also tested the entire strip one by one, and the entire strip would light up.

I have reached a standstill at this point.

What I have done:

Replaced the power supply

replaced the main board

replaced the t-con board

inspected and tested LEDs.

What should I attempt next? Could some LEDs be dim and cause it to not display? The next thing I can think about is possibly some wire went bad?

由完成的

I just reassembled the TV and I'm 100% sure the backlights are in working condition. Perhaps do you have any recommended measurements I should take? it could be the new boards are bad too.

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I decided to replace all wires.

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