avrdude: stk500_getsync(): not in sync: resp=0x00

Hey guys I just got into arduino uno and I was loving it. I got an UNO off of ebay (it might not be official I'm not really sure) and it was working fine. I uploaded the standard blink sketch and toyed around with it and my friend helped me make a cool fading sketch. All was fine- until last night when I tried using an external battery (actually ultra capacitors, but same idea). At first it worked and then I unplugged it and it the problem arose. The sketch was no longer on the arduino. I tried to re-upload the blink sketch to the arduino and got this error " avrdude: stk500_getsync(): not in sync: resp=0x30 ". I tried again today and now I'm getting " avrdude: stk500_getsync(): not in sync: resp=0x00 ". I know its not the ports, its worked before on the same exact ports. I'm afraid that maybe when I disconnected the power some wire might have contacted something on the board. I'm brand new to this so any help at all would be appreciated. Do i need to replace the Atmega or is it worse? Also, on a side note, when I got the board I noticed that the power on LED is sort of a red orange and L13 is green... Isn't that backwards? Could i easily switch the two? Thank you so much,

An arduino newbie

Start with some basic trouble shooting. With nothing connected and the board powered via USB cable, do you see +5, 3.3V on the power header?

If yes, try the Loopback test, see if the USB interface is working. http://arduino.cc/forum/index.php/topic,73748.0.html

Once you confirm the USB interface is working, can proceed to trying to upload a sketch again.

LEDs can be removed & swapped if you have surface mount rework capability. They are only indicators and color is not critical to anything, merely On or Off.

Thanks, but as I said, I'm new to arduino so I don't have a USB to serial adapter :( any other suggestions?

Also, as I've just noticed, " avrdude: stk500_getsync(): not in sync: resp=0x00 " shows up when there is no jumper from tx to rx. When there is, the error message is " avrdude: stk500_getsync(): not in sync: resp=0x30 ".

You have a USB/Serial adapter built into the board, its the 8U2 aor 16U2 chip.
Pull the AtMega328 chip out of it socket, put a wire from D0 to D1, and try th loopback test.
If that fails, you’re dead in the water because your USB connection to the outside world is gone.
You can get an external USB/Serial adapter, such as FTDI Basic

and connect it to header pins in place of the dead chip on the board.
Order a 328P while you’re at it in case that is blown also.

especially if yours feel warm/hot when power is applied - thats usually an indication that an IO pin has been damaged.

Thank you for the help, but I'm still confused. I've pulled the atmega, what do you mean by D1 and D0?

The pins marked D0, D1 on the header. Might also be labelled Rx, Tx.

So I think I've failed the feedback test... what now?

Revert to Reply #4 unfortunately. The 8U2/16U2 will not be replaceable by you. I don't even have the means to do it.