The following are the main reasons for the low output voltage:
1. Switching power supply short circuit failure (especially DC/////) short-circuit or poor performance, etc. At this point, first disconnect the switching power supply circuit all the load, check that the switching power supply circuit fault or the load circuit is faulty, if the load circuit is disconnected and the voltage output is normal, the description is overloaded, or the switch power supply circuit is still not normal.
2. Output voltage terminal filter Capacitor or rectifier diode failure, can be judged by substitution method.
3. The performance of switching tubes decreases, which leads to the failure of normal conduction and the internal resistance of the power supply increases and the load capacity decreases.
4. Switching transformer is bad, not only causes the output voltage drops, simultaneously causes the switching tube to the insufficient stimulation thereby damages the switching tube
5.300V filter capacitor is poor, resulting in poor power load capacity, a load of output voltage will fall.