A customer brought in a repaired TCL color TV model NT21228. The user mentioned that after some time, the TV would not turn on anymore. When I arrived, the indicator light was on, but neither the remote control nor the front panel buttons could power it up. When the set-top box was connected, there was no response at all. I suspected a lightning strike and the owner agreed to bring it home for further inspection.
I first checked the motherboard visually and noticed that a copper trace had burned out, though it wasn't too severe. I then tested the two transistors connected to that area and found them damaged to different degrees. I replaced both, but the issue remained. Measuring the +B voltage showed 35V, which is typical for standby mode. Checking the SCL and SDA lines, I found around 4V. Even after removing the memory chip, the voltage didn’t change. Testing the large SCL and SDA pins, I got a normal 5V, so I concluded the main IC was faulty. I replaced the main chip with an OM8370PS/N3/1/1680, along with the memory chip. After that, the TV turned on with the button and produced sound.
However, the repair wasn’t complete yet. When I input a signal (which wasn’t plugged in at the time), the TV showed no noise, the AV input was black, and then a protection screen appeared. When I connected the AV cable, there was still no picture or sound. Further testing revealed a blown voltage-stabilizing diode in the conversion circuit, and a damaged transistor. After replacing those components, the picture returned to normal.
I ran the TV for about an hour, and when I tried to turn it off with the remote, there was no response. I used a phone camera to check the remote signal and confirmed it was working properly. Then I turned the TV back on, removed the receiving board, and measured the 5V supply, which was fine. However, the voltage at the infrared receiver terminal was nearly zero. I found that the power supply resistor had turned black. I replaced the 100-ohm resistor and the infrared receiver tube, completing the repair of this color TV.
Replaced Parts:
Normal Machine:
Tinned Copper Clad Aluminum TCCA
Copper Clad Aluminum Tinned Wire,Tinned Copper Clad Aluminum Audio Cable,Tinned Copper Clad Aluminum Alloy Wire ,Copper Clad Aluminum Tin Plating
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