UPDATE :
I have made some additional research and I could not fin what is my problem, but I have made some tests listed below (The Arduino was supply via the 5V USB cable port during the tests):
- When the Arduino and the ramps are connected via USB, the LCD screen works but when it is connected to the power supply, the screen is all white.
- When the two boards are connected to the power supply, the fried smell come back.
- I am able to download the marlin firmware on the Arduino.
- The 5V pin on the ramps and on the Arduino shows around 5.60V while the 3.3V pin on the Arduino shows 3.65V.
- I measure the voltage on the 3.3V and the 5V regulators and both shows 5.6V which is strange for the 3.3V, because the 3.3V pin shows the good voltage.
If the problem is the 3.3V voltage regulator, is it possible/easy to change?