Which is the common fault of switching power supply? I found that only a small number of components failed in the switching regulator power supply. The common fault is the switching transistor itself. The transistor short-circuited, causing a large amount of current to flow through the transformer and blow out the fuse.
Transistor faults are usually caused by bad capacitors. Find expansion or leakage of output filter capacitors generally. Any capacitor that looks bad should be replaced. To prevent this common failure from occurring again, replace the output filter capacitor with a capacitor. These capacitors are designed to cope with strict filtering in switching power supplies. Most power supply manufacturers do not install low ESR capacitors as raw equipment because they are more expensive than conventional capacitors. However, using them as replacement components is worthwhile, as they will greatly power the service life in the field. When I use power, I replace the output filter capacitors with low ESR capacitors, no matter how good or bad they look. Since service calls cost much more than capacitors, this is a prudent move.
Secondary pipe failures are another common problem. There are many secondary pipes in the switching power supply. The failure of one of the secondary pipes will cause the power supply to blow a fuse or shut down. A common secondary fault is a +12 - or -5 - volt output rectifier short circuit. The failure of these secondary pipes will not blow out the fuse. The power supply detects short circuit and shuts down by itself. Some of these failures may have been caused by the use of +12 or -5 volts to power the coin door lights. In the power supply, the output is not overcurrent protected. A short circuit in the lamp holder may burn out the secondary tube by drawing too much current from the power supply. If a 6 volt bulb is inadvertently used instead of a 12 volt bulb, the +12 volt secondary tube may burn out. High voltage input secondary may also short circuit.
