Introduction: LCD TV Backlight Repair From CCFL to LED

While reading and browsing instructables on Arduinio CNC and related topics, I came across with one instructables that caught my attention. This is replacing the "LED Backlight for An LCD Monitor or Television" with LED Strip. I have an old defective LCD 13" TV around for ten years. I already discarded the casing, what is left is the metal part that support the Logic Board, Power Supply , Inverter and LCD. I did not trash because I was hoping to get parts for future projects. The problem with this LCD TV is the 2 second auto shutdown, during that time, I dis assembled the TV hoping to repair. I was able to isolate that when, the inverter/LCD is removed, I can hear sound of the TV, meaning it is working without the display. But I do not know how to repair that part, and so it went to stock area for a long time.

Until recently after reading that article, I tried to repair the TV. Able to isolate the Inverter and removed the CCFL to test, and lo and behold, the other side of 4 CCFL inverter is defective. The mosfets are shorted. I tried to use only the other side by cutting traces and isolate the shorted parts, but still the TV auto shutdown. Putting a flashlight into the screen will show that it is working. My option is to buy universal inverter since both CCFL still working, but I like better the LED strip option since this is cheaper and safer. I created relay switch so that the LED strip is off when TV is off also. I know this is not the best option, but for this, works perfectly and served my purpose. This is also very cheap and quick repair. I spent around $4 only on this.

Parts :
LED White Strips - 2 ( 10 inches each )

LED Red - 1 ( For relay indicator )

12V Relay - 1 ( Normally open from an old TV board )

BC547 (NPN) - 1 ( For relay switch )

Diode (Rectifier) - 1 ( For relay protection )

Resistor 10K - 1

Resistor 1 K - 2

Assorted Wires - For connection

Breadboard - 1 ( For the relay switch circuit )


Warning : Please always work safely and respect any power source even if it is low voltage. This project will require working with TV power supply and high voltage Inverter. I am not responsible for any harm or damage to anything it may cause to anyone that will try this instructables. Remember to remove power and allow time to deplete the power before working on the board.


Step 1: Remove CCFL From LCD Screen

Remove the LCD panel from the TV case and extract the CCFL , taking extra careful not to break anything specially the CCFL, LCD board, etc.

Step 2: Determine the Required Length of LED Strip

Measure the total length of the CCFL and match the LED strip, this strip can cut for every 3 LED. I bought mine from local electronics shop. They sell per 3 LED's.

Step 3: Connect Wire to LED Strip

Solder the wire on each LED strip, I did this by scratching the self adhesive tape at the back of the strip copper pad. Take note of the polarity and color of the wire to use to ensure that correct potential is provided on each pad.

Step 4: Build the Relay Switch Circuit

Assemble the relay switch as per schematic and test using any available 12V power supply. I added an LED indicator to know that the relay is activating and triggered with a 5V source. I used my homebrew electronics lab with PC power supply to test the circuit.

Step 5: Identify Relay Circuit Trigger Pin to Activate When TV Is On

From the inverter connection, locate the pin where it is "Zero" when the TV is off and with any voltage when the TV is on. In this TV I located the one with brown wire. This is using voltmeter and found to be around 3 volts. This is enough to drive the NPN transistor and eventually energize the relay.

Step 6: Connect the Relay Circuit to the Logic Board

Connect the relay switch Vin to the 3 volts pin, the power of 12V and to ground. Switch on the TV and see if the relay will activate. I removed the connector from the defective inverter and soldered to the relay board.

Step 7: Re-assemle the LCD Panel With New LED Strip

Assemble the LCD panel together with the LED strip and connect to the relay switch. Ensure to test first prior assembling so that you don't need to re open again when there is problem.

Step 8: Finally - Connect the New Relay Circuit and LED Strip Together and Enjoy

Replace the inverter board with the relay switch and assemble the TV. Power on and enjoy watching! I enjoyed this activity specially when I saw the TV working again. Have Fun!