Arduino Duemilanove usb power problem

Using Arduino IDE 1.x
1

i think i wired my arduino wrong and now my arduino will not power up over usb if i attach my battery and plug in usb i can still use it but idk what is up
i tryed other cables and none worked

im not sure but i think i connected 5volts to gnd on accident could that mess it up like this

sorry if this is stupid

thanks for any help

2

and when you plug in battery, then plug in USB can you upload sketches ?

3

yes it works just fine other than no usb power

4

Here's the schematic of Duemilanove http://www.arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf
You see there's a 500mA fuse that goes from USBVCC to VCC pin on FT232 chip. Fact that you can upload sketch means that chip is fine. So maybe this fuse is damaged you can find out if this is the problem this way:

connect arduino just to USB on you computer and then short this fuse (connect wire between sides) if board turns on just change the fuse if not you have probably destroyed some of the parts of USBVCC from the schematics

5

i shorted the fuse like you said it dose not come on i also test the fuse with a continuity tester it says it has continuity

6

That means USBVCC circuit is somehow destroyed maybe transistor or something. In that case check those parts if none of them is burned. As a partial solution you can use trick that is used in nano http://arduino.cc/en/uploads/Main/ArduinoNano30Schematic.pdf
it's a 5V schottky diode between USBVCC and +5V on the board.

7

matthewpepperl:
i shorted the fuse like you said it dose not come on i also test the fuse with a continuity tester it says it has continuity

A fuse with continuity is a good thing. They are suppose to be shorts (until something goes wrong.)