Ethernet shield capable to kill Arduino or vice versa?

Development Tools IDE 1.x
1

Hi,
a month ago my Arduino Mega died. It powers up, but refuses to communicate. I had no "safety" resistors on pins and though there wasn't any obvious incident, I was trying to use H-bridge DC motor driver IC, which possibly was damaged, so I assumed that the reason was a short circuit somewhere + my stupidity.

Mega was paired with Ethernet shield (WIZnet).
Now I tried to plug that shield into UNO and UNO refused to power-up. Then (I know - I often get dumb ideas :slight_smile: ) I plugged the shield while it was running and power LED of both Arduino and Ethernet shield slowly faded out. Luckily UNO is fine, but I remember alike behavior a couple of times when Mega died (it turned on, then power LEDs slowly faded out, a reason UNO is alive might be that it's connected to usb, not a 30A psu like Mega was). So the question is - is Ethernet shield capable of killing Mega and how to get a clue of what's wrong with it?
Or might a short on Mega's pins damage the Ethernet shield? (Ethernet shield pins were not connected to anything)

2

Slowly faded out. That sounds like the usb power fuse activating. It is the auto-reset type. Check the +5v pin with a voltmeter. Are you getting 5 volts there?

It could be the ethernet shield is bad and is drawing too much current. But that is just a guess.

3

SurferTim:
Check the +5v pin with a voltmeter. Are you getting 5 volts there?

Thanks for reply.
If I would I'd probably have good chances destroying my UNO too. But checking resistance shows something interesting - there's 2 Ohms between 3.3V and ground vs 1K precisely on a healthy board I got today. Not too good at distinguishing PCB traces, but it appears the difference comes from that "heatsinked" component that looks like voltage regulator near Ethernet port. I probably need to find schematic of Ethernet shield and try replacing that thing.
Edit: after desoldering - it's not the regulator's fault :slight_smile: Short is still there