How to test Voltages to Determine No Backlight Symptoms
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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.
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