Xiahua color TV TS2580 "three no" fault repair process - android - Phones Developers

There is no response to power up. After unpacking the back cover, I found that the fuse had been blown, and it was like this.

The resistance of the 300V filter capacitor C507 is about 2KΩ. If there is a short circuit or leakage, when the jumper of the degaussing resistor is disconnected, it is also found that the degaussing resistor has also been deformed, and it looks like this.

Then disconnect the jumper connected to the drain 1 of the N501 power block. The resistance at both ends of the C507 is still about 2KΩ. Look at the electrical schematic. Only the one-pin wafer capacitor C508 of the R509 and N501 start resistors. Connected to the large electrolysis C507, continue to measure the starting resistance of the R509 bright pin in the path is normal, and finally only the small capacitor of the wafer is left. Looking at the circuit diagram on the motherboard, I found that the C508 capacitor on the side of the switch transformer has cracked, no wonder not seen. Decisively remove the capacitor C508, measure the resistance of this capacitor is about 2KΩ. At this time, measure the resistance of the two pins of the motherboard C507 again and again, there is obvious swing of the forward and reverse resistance.

At the same time, no obvious short circuit exists in the output of the secondary of the switching transformer. Replace this C508 capacitor (1000/1KV), for safety reasons, replace the capacitor withstand voltage up to 2KV, temporarily do not connect the fuse, and connect an incandescent bulb here, power on, its bulb is intermittently illuminated, indicating that Can be used normally. At this point, replace the fuse, replace the degaussing resistor, connect each plug, the sound of the boot picture resumes normal viewing.
Analysis reason: due to the heat generated during the degaussing resistance, and the thin solder layer of the lead, resulting in a virtual soldering, and at the same time it seems to be connected, causing a rise in the reverse peak voltage, and the C508 wafer capacitor has been used for performance and use. For a long time, plus external factors such as dust, causing breakdown, causing over-current to cause the fuse to burn, and also avoiding greater damage.
A recent photo of the upstream output parameters is attached.