I'm experiencing an issue with an Arduino Mega 2560 : I powered the board through the Vin using a +24 --> 9V voltage regulator. When I power the board and measure the 5V output from the board, the voltage quickly drops from 5 to ~3V within seconds.
However, while powering with USB, the 5V output from the board gives us a clear 4.8V.
I have checked the 9V Voltage regulator (connected to the Vin), and it has a +24V input which remains stable (as should the 9V).
Any thoughts ?