Here's what the reverse engineered circuit looks like:
X----->|--------o------------o--------------o Vcc 1N4002 | | | | + | | 470 uF ### 0.1 uF --- 25 V --- --- | | | | X---------------o------------o--------------o Gnd
The wall wart connects to the X terminations on the left. The caps are common and their purpose is understood. What purpose does the diode serve?
Thank you,