t's a long story. I was trying to solve my printing problem described in this post. The printer was connected to the computer then and the power is on. I was adjusting the current of my y-axis motor, and I accidentally touched something with the screwdriver. Then the driver of the motor sparkled in an instant. I didn't realized that it's a problem until I checked my computer after all those thing happened, I found that it disconnected by itself. The fan on my PSU was on and the LEDs on Mega and Ramps were on and everything seemed on.
However I just couldn't connect it again. I believe that the usb cable is fine. The usb cable was providing power to mega, because even when the main PSU is unplugged the led will still be on if the usb cable is connected.
When I tried to connect the printer while the usb cable is connected Printrun said:
"[ERROR] Could not connect to /dev/tty.usbmodem1411 at baudrate 115200:
Serial error: could not open port /dev/tty.usbmodem1411: [Errno 2] No such file or directory: '/dev/tty.usbmodem1411' "
(115200 is my usual baudrate.)

So, is any of my parts broken? Or will the problem disappear in some time?

Try connecting the usb with the ramps removed. If it connects check the diodes. I think it is d2 behind the fuses that burns out and sends power down the USB. if you run with the USB connected all the time, then remove that diode, and see if it will connect with the ramps connected.. you may want to pull the driver boards also to test.

It doesn't connect even without Ramps. So I'm getting a replacement now. Thank you!

Now everything's new, but I still cannot move my motor...
I am able to connect it to the computer, but it stays "5 commands waiting" forever if the main PSU is connected to Ramps before it's connected to the computer. If connect Arduino first, with the main PSU unplugged, the "5 commands waiting" will disappear.
I am using sprinter firmware and ramps 1.4+Arduino

edit: I just tried marlin firmware and got the same result. (baud rate varied)
The main PSU seems working fine, tested with 12v fan. LCD lit up. Motors should be fine, too, because the heater didn't work as well.

Can anyone just tell me why? Thanks a LOT!

Edited 2 time(s). Last edit at 02/14/2014 04:29PM by jpan.