The voltage regulator clamps the voltage in the switching power supply to protect the circuit and prevent other devices from being damaged by overvoltage; Other circuits need accurate voltage, and the voltage needs to be stabilized by voltage regulators. According to your description, your original board is a 4. 12V voltage stabilizing tube, but when you use a 4.2V tube, the voltage is stabilized at 3.85V, which shows that this tube should work, but its performance is not as good as the original board, and its dynamic resistance should be relatively large. And you switch to 5.2V In fact, at this time, your regulator is no longer working. The voltage on your circuit (without regulator) should be 4.22V Your circuit should have high requirements for this voltage, so it will be clamped with 4. 12V; So if you change it to a big one, it will definitely be bad for the circuit. It is better to replace it with the original board. If it really doesn't work, use 4.2V V.