NodeMCU ESP8266 Power Supply Issue

Hello guys, I would like to ask some questions here for my project.
I have a NodeMCU ESP8266 board. Previously, I powered it up using a 12V power supply, then through a L7805CV to regulate the voltage down to 5V. The 5V is connected to the Vin and GND of the board. It works perfectly throughout the project, but due to some mistake I accidentally reversed the polarity of the power supply, which means the 12V and GND was reversed. Then it went through the voltage regulator towards the board. Nothing powers up.
After realizing the mistake, I have connected the power supply properly. However, it couldn't power up the board anymore.
I have done some testing here

  1. Without connecting the board to the PCB, the voltage regulator output was 5V. After connecting the board, the voltage at Vin is around 1.9V only, and the board doesn't powers up.
  2. The board still works perfectly if I powered it up using USB.

Can anyone guide me on troubleshooting the issue?
Thanks.

which particular ESP8266 board are you using?

Sounds like you burned that regulator! But if the board still functions on usb power then I guess the board’s esp chip and on-board regulator have somehow survived.

If you replace it with another regulator, wire a diode in series with the regulator input, for protection from further accidents.

I would use a DC-DC converter module, adjusted for 3.3V, and power the board through the 3V3 pin. But perhaps you need a 5V supply for some reason. It’s hard to give good advice with so little knowledge of your project and other components in it.