Arduino Uno or Ethernet Shield not working anymore (power issue?)

Hello everyone,

After years of loyal service, my favorite Arduino project stopped working the other day and I can't figure it out. I am looking for suggestions.

The project uses an Arduino Uno (rev 1) and an Arduino Ethernet Shield (rev 1 too). I uploaded the simple blink example sketch that comes with Arduino IDE to exlcude any software issue.

When the Ethernet shield is unplugged, everything works fine (the LED blinks) using either USB power or a power supply. Once I plug the Ethernet Shield back, the Arduino LED blinks when I use USB power but not when I use the power supply! The Arduino ON led turns on but that's it (none of the other LEDs on the Arduino or the Ethernet Shield turn on or blink).

I measured my power supply with a multimeter and it provides 8.8V and the Arduino Uno official page says:

"The board can operate on an external supply of 6 to 20 volts. [...] The recommended range is 7 to 12 volts."

So I think my power supply voltage is ok. I was thinking it could be a an issue with the amperage then (maybe it degraded over time). But where/how I can measure the amperage drawn by the Arduino while it's plugged since I can't access the inside of the barrel connector? Is there somewhere on the Arduino were I can put my multimeter probes to measure the current drawn?

Aside from that, if anyone has any idea of what might be going on, I would be most grateful.



If you are supplying 8.8 volts to the barrel connector, then check the voltage between the 5v pin and ground. It should be 5 volts. If it is more or less than 5 volts by more than a couple tenths of a volt, you have a power supply problem.

Hi SurferTim,

I have 3.1V without the Ethernet Shield, and 0V once the shield is plugged in. I guess I am buying a new power supply then :)

Thanks a lot,


PS: I borrowed the power supply from another project (how did I not think of that earlier!) and it works so it's definitely a power supply issue

Thanks again.