To check the TV power supply directly, we turn off the load, which is usually the horizontal output stage, and cut a V light bulb to the vacated contacts. Next, we check the input circuits, the mains rectifier, the filter capacitor that stands after the mains rectifier, and the powerful transistor of the power supply.
If the lamp does not light up at all, you need to look for a break in the mains rectifier, filter, in the capacitor, which is immediately after the mains rectifier. Often, in the event of a malfunction breakdown of the electrolytic capacitor connected after the mains rectifier, the current-limiting resistor or filter choke, as well as the rectifier diodes, burn out.
If, when turned on, the lamp replacing the fuse lit up and immediately went out or began to glow faintly, and the lamp connected instead of the sweep circuit lit up, then we can assume that the power supply is working properly, and further adjustment can be made without the lamp. If, however, the lamp connected instead of the scanner does not light up, then you need to look for a malfunction in the power supply. First of all, measure the voltage across the largest capacitor of the power supply this is usually the capacitor included at the output of the mains rectifier.
The voltage across it should be somewhere around V. If it is much lower or absent altogether, then the fault must be looked for in the mains rectifier, circuits from the mains to it, as well as in this capacitor itself. Here is such a malfunction - the scan is working, the screen is lit, but there is no image. In this case, the faulty node can be identified as follows. If there is no sound and image, the malfunction should be looked for in the radio channel tuner, video processor.
If there is sound, but there is no image, the malfunction should be looked for in the video amplifier or video processor circuit. External manifestations: The TV makes attempts to enter operating mode and can turn on only after repeated such attempts.
Power module needs repair. The defect progresses every day, as a result, the TV will not be able to turn on at all. External manifestations: TV does not turn on at all. There is no indication by indicator lights. The defect is usually eliminated at home by the customer. External manifestations: No image, there is sound.
Malfunction of the inverter — power converter backlight lamps TV. On televisions with screen sizes less than 26 inches, the defect is usually easily fixed at home by the customer.
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