Hisense LCD TV 42K431DX4F automatic shutdown fault repair example - appliance repair - Database & Sql Blog Articles

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Hisense 42K431DX4F LCD TV experiences automatic shutdown, and the PS-ON/OFF signal measures 0V, indicating a potential issue with the motherboard. Further testing shows that the CPU power supply is not providing the expected 1.25V. Inspecting the DC-DC circuit for the CPU, specifically component U5, revealed some irregularities. A detailed image of the circuit was captured for reference.

During testing, the voltage at point C increased from 0.8V to 2.7V. At this point, the voltage at D stabilized at 1.25V, allowing the CPU to function normally. However, when the fault occurred, point A remained at 5V, while point B dropped rapidly before slowly rising again. This behavior suggested a problem with diode D3. Replacing D3 resolved the issue, and the TV returned to normal operation. The repair process highlights the importance of careful voltage monitoring and component testing in diagnosing power-related faults in electronic devices.