Reasons and solutions for the power adapter not connected to the load and no voltage
If the power adapter is not connected to the load, the measured voltage drops from 12 volts to 1 volt or no voltage, indicating that the power adapter is caused by component damage, and the fault is generally caused by components such as rectifier diodes and filter capacitors.
Whether it is a tablet computer, a wireless router, a network set-top box or other electrical appliances, when the power adapter has no voltage output, it means that the power adapter has damaged components.
Specific inspection method: measure the output voltage of the power adapter with the voltage range of a pointer multimeter at 50 volts or a digital multimeter at 200 volts. If the measured voltage is 0 or about 1 volt when the load is not connected (that is, not plugged into the electrical appliance), it is obvious that the power adapter is faulty.
For some small power adapters, most of them are disposable and cannot be disassembled smoothly. It is not as easy to disassemble as the charging head of some jukeboxes. This kind of power adapter shell seems to be cast in one piece, and it is not easy to open or can't be opened directly. I once repaired the power adapter on a wireless router. The fault phenomenon is that the power output 12V voltage is 0. We can't disassemble it normally, but we had to use a saw blade to slowly pull the power adapter from the middle along the sealing line. Then, after measurement and inspection, the rectifier output diode was short-circuited and damaged, and a high-power rectifier diode was replaced, and the output of 12 volts was measured with a multimeter, and the fault was eliminated.
Like the small power adapter mentioned above, if the output voltage of 12 volts becomes about 0 or 1 volt, most of the rectifier diodes or filter capacitors are damaged. Just replace the damaged components. If the fault is not completely eliminated after replacing the vulnerable components, it is recommended to buy a new power adapter of the same type. When replacing the power adapter, pay attention: the voltage polarity of the output terminal of the power supply must be the same as the polarity of the original power adapter, otherwise, even a good power adapter will not work normally, which will cause misjudgment and mistakenly believe that the electrical appliance used is damaged. This must be noted.
There is also a power adapter that is currently used on LCD TVs, generally used on small LCD TVs of about 17 inches. This kind of power adapter generally outputs 12 volts. This kind of power adapter is relatively large in size, and the components used inside are also relatively good, so it is not easy to fail in general.
If this kind of power adapter has no output voltage or is very low, the maintenance method is basically the same as that of the small power adapter. Mainly check whether the rectifier diode, filter capacitor and other components are damaged, and replace the damaged components. If the power adapter fails or is still abnormal after replacing the obviously damaged components, it is recommended to directly purchase a power adapter of the same model. The matters needing attention are as mentioned above and will not be repeated here.
The above mainly introduces two kinds of power adapters. When the output voltage of 12 volts becomes 0 volts or 1 volts, the repair methods and treatment suggestions are introduced.