A customer with a repaired TCL color TV model NT21228 reported that the power switch was unresponsive after some time. When I arrived at the location, the indicator light was on, but neither the remote control nor the front panel buttons could turn the TV on. Even when connecting the set-top box, there was no sign of activity. I suspected a lightning strike and the owner agreed to bring it home for further inspection.
Upon initial inspection of the motherboard, I noticed some copper foil damage, though it wasn't severe. The two transistors connected to that area were also damaged to different degrees. I replaced them, but the issue remained unresolved. I measured the +B voltage, which was 35V—clearly in standby mode. Checking the SCL and SDA voltages showed around 4V. After removing the memory chip, the voltage remained the same. Testing the large SCL and SDA pins, I found 5V was normal, so I concluded the main IC was faulty. I replaced the main chip (OM8370PS/N3/1/1680) with a socket, swapped out the memory block, and the TV turned on with sound.
However, the repair wasn’t complete yet. When I input a video signal (it wasn’t connected at first), the TV had no noise, the AV input showed a black screen, and then the protection screen activated. 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. After replacing the damaged transistor, the picture returned to normal.
After an hour of testing, the TV would not shut down using the remote. I used a phone camera to check the remote and confirmed it was working properly. Then, I turned the TV back on, removed the receiving board, and measured 5V, which was normal. However, the voltage at the infrared receiver terminal was close to zero. I discovered that a 100-ohm resistor in the power supply section had turned black. I replaced both the resistor and the infrared receiver tube, and the TV was fully repaired.
Replaced Parts:
Normal Operation:
High Purity Copper Clad Copper,Copper Clad Copper Bare Copper Wire,Double Layer Bare Copper Wire ,Electroplated Copper Clad Copper Core Wire
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