thanks for the support one reply all day long

Im new to ardiuno and I guess im on my own, one reply, all day

I supplied my mega 2560 with dc 12v 600 ma adaptor to the dc plug on the board and poof. I read they can handle up to 20 v but should only use 12v, it ran fine on the usb. but when I plugged in the 12v 600 ma power to the dc connection on the board ,it melted a little ATMEL16U2 chip next to rx/tx leds any reason why this would happen, anything, anybody

Where did you supply this power (what pins/jack?)

the dc input jack on the board all I did was unplug the usb connection and plug in my ac adapor witch is output 12v 600ma I had a tft lcd running a program called stilo v3.0 aquarium controller and 3 leds on pin 8,9,10 with 1k resisters when i suppyed the dc 12v to the board the srceen started to flicker I checked the 5v on the board and it had over 7v on it and then came the smell of burning I looked at board the ATMEL 16U2 melted , can anyone tell me why it would melt that chip

Did you check for correct polarity of the 12v input. I think in the past I reversed the 12v input to a 7805 chip. Started smelling something hot, checked the chip and it would sizzle spit. The 12v came from a wall wart, so that may have saved the chip as it worked correctly after swapping the 12v leads.

yea the polarity is right. Crossroads told me to check the DC output on my 12v 600 ma adaptor and I got DC 17.5v A little high I think its no good, but still the board should of handled it. Thanks for responding, Im new to this ardiuno, had my board 1 week and its fried, last week had rtc problem puting out 165 165 85 165 165 2165 for time and date asked everyone, read forums, finaly on this site learned that i dont need pullup resisters and they were on the rtc had to remove them. Thanks Alan

I would not be confident that the arduino can actually handle 17 volts.

yea I found that out , fried my board :(, hope to have another in the mail soon :D Thanks Alan