Arduino heat problem

Using Arduino IDE 1.x
1

Hello, good morning.

Currently i'm having one problem with my Arduino, related to the voltage regulator.

When I plug my arduino directly to the USB, my Voltage Regulator gets really hot and after few seconds all the led lights lose bright and I lose USB connectivity to the arduino.

What is strange is that there are 3 different situations:

1 - When I plug just the arduino in the USB cable = VR really HOT

2 - When I first plug external power supply AND THEN plug USB cable JUST in the Arduino = VR ok, not getting hot.

3 - In situation #2, when I do it WITH the Ethernet Shield, it starts getting hot.

Do you have any knowledge to share about this?

Thanks!

2

Something wrong with power source circuit. Which Arduino exactly?. Genuine Arduino Mega or UNO has P-MOSFET which acts as switch between jack and USB and his actuator is OA as comparator - compares 3.3V against Vin from jack plug. Check the transistor and OA first, 5V regulator seems to be ok according the situation #2.