Today, I was called in to repair a Skyworth 21N16AA TV. The user mentioned that the TV makes a "squeaky" and "clicking" sound. When I opened the cover, there were no obvious signs of burning on the high-voltage pack or the high-voltage cap. Based on my past experience, this type of issue often relates to an increase in the voltage rise.
To check if the B+ voltage was rising due to a problem with the power supply, I performed a test by shorting the secondary winding of the transformer and using a dummy load. The B+ voltage spiked up to 200V. If you have some repair experience, it's usually clear which component is at fault without needing further checks.
I measured the capacitance of C610 and found it faulty. After replacing it, the B+ voltage dropped to around 85V. But then I noticed something odd. The power supply section had been previously repaired, and the sampling potentiometer was turned all the way counterclockwise. It was centered, and when I disconnected the dummy load and reconnected the short-circuit line, the image lines appeared jagged and compressed on both sides. The B+ voltage didn’t improve much.
Looking at the image, I could guess where the problem was. It’s a common issue in this model. I removed the two faulty components and saw that one had failed completely, leaving a visible scar, while C610 was also damaged.
I replaced them with two new 160V/100U capacitors, but the TV still didn’t power on. I realized that C610, C615, and C616 are commonly faulty in this circuit. It seems the previous repair didn’t fully replace C610, which led to the B+ voltage increasing again. This caused the TV to malfunction and even sparked. This is a typical problem, and it's important for beginners to be cautious about B+ voltage issues.
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