Fixing Sonoff 4CH PRO Damaged Power Input Circuit

Even though the Sonoff 4CH PRO accepts a wide range of DC current input, the 4CH PRO is not protected from polarity inversions such that inverting the positive and the negative will blow out capacitor C23 as well as damage the the MP2307 power regulator.

One of the easiest fixes is to simply bypass the stepdown bridge located on the bottom right of the Sonoff 4CH PRO by using a small buck converter to step down to that is sufficient to power the Sonoff 4CH PRO.

The method used here actually desolers the MP2307 in order to reach the solder pads and to connect the leads directly to the IC pads.

        +---------+
        | MP2307  |
     ---+         +---      ^
        |         |         |
     ---+         +---      | Text on Sonoff Board
        |         |         |
SW +----+         +---
   |    |         |
GND| +--+         +---
   | |  |         |
   | |  +---------+
   | |
   | |
   | |
   | +-- GND
   |
   |
   +---- 3.3V input