LED Tube light Repairing. Home Utility Circuit 32


1ALED Tube lights are costly lights but susceptible to instant damage. Since it uses an LED Driver and very sensitive LED Chips, voltage fluctuations, voltage surge, over heating etc can destroy it easily. But all the parts of the LED Tube light will not fail, so that we can easily repair it. The major problem may be the failure of one or more LED chips or the driver. By doing some repair works, we can use the LED Tube light again. I found one of my 12 Watts LED Tube light is not glowing and decided to repair it. Now it is working well. Its expense was just Rs.50 for the driver only. See the step wise method of LED Tube light repairing.

The LED Tube light has an LED panel and an LED driver inside the case. The LED panel has many SMD LED Chips depending on the wattage of the Tube light. In the 12W Tube light, I found 24 LED Chips each rated 0.5 W. The LED chips are arranged in sections having 3 chips in each with a series resistor of 200 Ohms. All the three LEDs in each section are connected serially with the single 200 Ohms resistor. So the 24 LEDs are arranged in 8 sections. These sections get power through the parallel connection. So if one or more sections or even a single LED fails, the Tube light may light partially.
1B
The LED Driver is a small SMPS that converts 230V AC to 12V DC with a current capacity of 1 Ampere. In other types such as 9W, 5W, 3W Tube lights, the Drivers will be 9V, 5V, 3V etc. The LED driver is sensitive to voltage fluctuations so it can fail at any time. If the driver fails, the Tube light becomes useless. We can replace the LED Driver and its cost is low now.
1C
Let us see the step wise method to repair the LED Tube light.

When I connected the LED Tube light to mains, I found that it is not glowing.
1

Opened the Cover of the LED Tube light to see the damages occurred
2

Removed the Driver from the LED Panel and provided 12 V , 1 Amps power from the Bench power supply. I found that one section of the LED panel is not working.

3
Identified the LED Section which is dark. It was L 28, L29, L30 section. Tested each LED using 3V to identify the damaged LED. I found that LED L29 is not glowing. That is why the remaining LEDs are not glowing.
4
Shorted the damaged L29 LED with a wire and tested again with 12V. The other two LEDs (L28 and L30) worked. So the problem is in L29.
5

Removed the wire and shorted the damaged LED with a Jumper. It was a cut lead of a resistor.

6

Tested again with 12V. Now except that shorted LED, all the other LEDs worked well.

7

Now the LED panel is OK. Then checked the LED driver using a volt meter. No output voltage came from the driver. That means it is damaged permanently.
8

Took a New 12V LED driver

9

Connected that new LED driver to the LED panel

10

Again tested by connecting the LED driver to Mains. The LED Tube light is working and all LEDs except the shorted one are in full brightness

11

This is the repaired Tube light

12

Covered the LED driver using heat resistant insulation to avoid accidental short circuit when contact with the aluminium case

13

Pushed the LED driver into the aluminium case

14

Replaced the cover and now the LED Tube light is in a new form

15
Connected to Mains. Well , the LED Tube light is glowing well.
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