HELP! Arduino Mega 2560 and Ethernet shield problem...

Sorry for my English..

I have a weird problem in my ethernet shield and arduino mega 2560 and i need help!

Just finished my project after 1 month of development and it was time to make the final product connect the thing up and give it power from a AC/DC adaptor.
i used a 12V 1.0Amp adaptor.

in the beginning i was connecting flawlessly to the arduino web server , but after a while , i saw erratic behavior from the Ethernet part of my project. the ethernet shield was rebooting every time i was trying to access it from the web page. or even when i was trying to PING.
I inspect the damn think and i saw that the voltage regulator of the mega was overheating. but also the central chip of the Ethernet shield was overheating too.

Next Step i try a 7.5V 2.0Amps AC/DCadaptor, After that the Voltage regulator of the MEGA was cool but not the ethernet shield too. and the problem persist.

Next Step i connected again to my development environment, with my laptop power it from USB cable and i also put small heatsink into the Ethernet shiled central microchip to prevent heat.
Unfortunately the problem isn't gone , some times it working some times not. What should i check Please help me

The w5100 does run a bit on the hot side. Check the voltages. Is the 5v bus on the Mega still 5 volts? Is the 3.3v regulator on the ethernet shield still producing 3.3 volts?

thanks for your response
So you are saying to measure with a multiplier the voltage outputs?

Yes, measure the output of each regulator with a voltmeter. Voltage regulators have been known to fail under severe heat loads, and allow too much or not enough voltage onto the bus.

i measured from Ethernet shield 5v output and ground
4.78 V when i hit the URL to connect the trafic lights from UTP goes OFF and i get 4.75V and i lost the conection.. there is defenetely something wrong , i checked another ethernet card i have and there is no problem

Sorry the Ethernet card 3.3V is OK , gives me the 3.3v even with the "autorestart" when im trying to connect

What do you mean by "autorestart"? What are the symptoms? Does the Mega restart also?

No the Mega is working great at it should.

The symptoms are when i hit the IP of the arduino , or when i Ping (when i send data) all the leds from the ethernet shield goes OFF plus the 2 small leds near the ethernet cable and goes ON again , and i get no response. like restarting it self when i try to communicate

All the LEDs? Even the shield "ON" LED? If so, you have a power fail. The "ON" LED is lit by the 3.3v bus. If it is going out during this, the 3.3v bus on the shield is failing.

Only the PWR is constantly ON! all the others goes off and on

I do not see a PWR LED on my shield, just ON. Assuming that your PWR LED is connected the same as my ON LED, and all the other LEDs are controlled by the W5100, then I suspect the W5100 is failing.

can i re-flash the W5100 somehow?

I don't think so. I hear you can install new firmware in the ENC28J60, but I haven't seen a way to flash the w5100.

Nobody else with the same problem? :cold_sweat:

the shield cannot send data , the TX led never works. and when it should work, shield is reseting