Hisense LCD TV TLM32V68A frequent automatic start and stop fault repair example - appliance repair - Huaqiang electronic network

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

TP-IP4220CZ6 5V 0.35PF breakdown voltage 6V SOT

Shunuo varistor / ESD varistor / product complete / Sunlord first-class agent

In the afternoon, a customer brought in a Hisense LCD TV model TLM32V68A for repair. He described the issue and left his contact number before leaving. I placed the unit on the workbench 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 picture remained black for around ten seconds, as if the TV had been turned off by the remote control. Then, the image and sound would return automatically for another ten seconds or so. This cycle repeated continuously. The blue light stayed on throughout the entire process.

When I pressed the standby button after starting, the light turned red, and the TV went into standby mode. It wouldn’t restart again unless I turned the power off and back on. Once it started, all the buttons worked normally. I tested the shell separately and found no bulging capacitors on the high-voltage power supply board or the main board. The output voltages at the 12V and 5V terminals of the power supply were normal, and the input voltages on the main board also looked good.

I checked the three-terminal voltage outputs on the main board, and both 5V and 3.3V were stable. However, when I measured the voltage at component N6 (model SE8117TA, an adjustable three-terminal voltage regulator), it only read around 0.8V. This indicated that the chip was in a self-stop failure state. After waiting a bit, it briefly rose to 1.19V, which suggested it was in the self-start phase. Notably, this component was significantly hotter than its counterparts.

Upon closer inspection, I noticed that there was no voltage-regulating resistor between pins 1 and 2 of the transistor. Pin 1 showed a direct resistance to ground, which was unusual. Since the output should be around 1.19V during normal startup, I concluded that this was a 1.2V power supply line. I replaced the faulty component with an AM1117 1.2V three-terminal regulator from an old motherboard.

After the replacement, the TV operated smoothly for over half an hour, and the temperature of the new regulator was much lower. I reassembled the unit and planned to let it run overnight before informing the customer to come pick it up.