In the afternoon, a customer brought in a Hisense LCD TV model TLM32V68A to my repair shop. He explained the issue and left his contact number before leaving. I placed the TV on the inspection platform and began testing. When I turned it on, the blue light came on, and after about ten seconds, the screen turned blue. The AV audio was normal, but the image was black for around ten seconds, as if it had been turned off by the remote. Then the picture and sound would come back automatically for another ten seconds or so. This cycle repeated continuously. The blue light remained on throughout the entire process.
After starting the TV, pressing the standby button would turn the light red, and it would go into standby mode without restarting. If I turned it off and on again, the blue light would appear, and the TV would start up normally. All buttons worked correctly once it was on. I then tested the shell separately. There were no bulged capacitors on the power supply high-voltage integrated board or the main board. The output voltages of the 12V and 5V terminals on the power supply board were normal. The input terminals of the main board’s 12V and 5V were also stable.
I checked the three-terminal voltage outputs on the main board. Each 5V and 3.3V output was within normal range. However, when I measured the component N6 (model SE8117TA), which is an adjustable three-terminal voltage regulator, the voltage was only around 0.8V. It seemed to be in a self-stop failure phase. A few moments later, the voltage rose to 1.19V, indicating that the component was in the self-starting phase. I noticed that this particular transistor had a much higher surface temperature than similar components nearby.
Upon closer inspection, I found that there was no voltage-regulating resistor between pins 1 and 2 of the transistor. Additionally, pin 1 showed a direct resistance to ground. Since the normal self-starting voltage at the output should be around 1.19V, I concluded that this was a 1.2V power supply section that had failed. I replaced the faulty component with an AM1117 1.2V three-terminal regulator from an old motherboard.
After the replacement, the TV worked properly for over half an hour, and the temperature of the new regulator was significantly lower. I reassembled the TV and prepared to test it for a full day before informing the customer to pick it up. I also took some photos of the repair process for documentation and future reference.
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