Changhong rear projection TV CHD4379 after the fire black screen audible fault repair example - android - Phones Developers

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Maintenance Case: Changhong CHD4379 Rear Projection TV. The original issue was a fire in the high-voltage line inside the high-voltage package. The unit was immediately turned off, and the user was advised to replace the high-voltage package. After replacement, there was a high-voltage sound and a slight discharge noise. Upon inspection, it was found that the top of the high-voltage cable had a hole, and the filament was still working. The screen remained black, but there was sound, and the on-screen characters were normal. Further investigation into the ABL circuit revealed a blown 10K resistor. Continuing the check, the -217V power supply resistor R419, which provides voltage for the field scanning, was also open. Additionally, VD312 showed signs of wear, and the -414V resistor R414, responsible for the pillow correction, was also open. All these components were replaced. Despite these repairs, the TV still had a black screen with sound and normal character display. Following the ABL line back, another board was identified. Further testing showed that capacitor C211 had resistance. After removing the capacitor with a soldering iron, the boot-up process became normal. To prevent future issues related to moisture or short circuits, I applied 704 glue to the affected area. Additionally, a 20V Zener diode was connected to ground on the ABL line as a protective measure. The repair was complete, and the TV is now functioning properly.