A friend's Changhong PF2139 color TV frequently blows a 3.15A fuse when turned on. Once it starts, it works fine and can be watched normally. This issue lasted almost a year, and despite several professionals trying to fix it, the problem remained—fuses kept blowing intermittently. One day, he came to me with his frustration. Since he didn't have the tools at the time, he brought the TV home with him.
I decided to take a closer look. At first, I thought the problem might be with the A3 power supply, which is a common area for issues. However, the fuse was blown but not in a typical blackened way. There was some white smoke on the glass tube wall, suggesting it had been overheated. I wasn’t sure if the fuse itself was faulty or if there was an issue with the power supply components. I couldn’t jump to conclusions, so I took out the circuit board and found that the power supply had been completely altered. It looked like previous technicians had worked hard on it, but no obvious short circuits were visible.
I tested the fuse again with a 3.15A rating, and it blew immediately. I disconnected the C pole and removed the degaussing coil, then tried the fuse again. It still blew. Then I removed the three-terminal degaussing resistor and checked the four diodes for shorts. They all looked good. I tried using a regular 2A fuse, but it also burned out. At this point, my suspicion fell on the 400V filter capacitor.
I removed the capacitor and tested its charge and discharge. It was a 470uF/450V electrolytic capacitor, which should have been replaced by the previous technician. I tried replacing it with a 100uF/400V capacitor instead. After powering up, the voltage across the capacitor was 300V, which was normal. I reassembled the circuit and powered the TV on. The screen displayed a blue screen, and everything worked as expected.
To double-check, I used the original 470uF/450V capacitor in a 29-inch color TV power supply. It worked perfectly, with no issues even after multiple power cycles. This confirmed that the original TV had a large-capacity filter capacitor.
After analyzing the situation, I realized that larger capacitors can cause higher inrush currents during cold startup. If the fuse is too small, it may blow due to this surge. On the other hand, increasing the fuse size could lead to excessive current damaging the rectifier bridge, which would be more costly. Therefore, the power supply’s filter capacitor shouldn’t be oversized—it needs to be just right for the system.
Interchangeable Adapter refers to an adapter designed for versatility and compatibility, enabling users to effortlessly swap between different configurations to accommodate various devices or interfaces. These adapters offer several key characteristics and applications:
Power Conversion: During travel or international travel, Interchangeable Adapters convert power outlets from different countries to match the required interface for electronic devices, eliminating power incompatibility issues.
Data Transfer: Besides power conversion, some interchangeable adapters also facilitate data transfer between different interfaces.
Device Connectivity: They serve as a bridge to seamlessly connect devices with incompatible interfaces.
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