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Just finished a long calibration routine to discover that after all my fiddling with the endstops, etc, my extruder stepper had stopped responding to commands. I tested that it wasn't the stepper by turning off the board, swapping the stepper into the Z-axis socket, and running commands - and it worked. So not a problem with the motor.

But then when I re-swapped it back into position, the RAMBo seems busted... it turns on but the LCD says "killed," and while I can connect to it, upload firmware etc, it does not respond to commands to move the steppers or turn on the heaters.

Is it possible I sparked the board or something? Is there anything I can do short of forking over $200 for a new one?

First question, did you heat up the hot end before trying to move the extruder motor? If it was cold, the extruder won't move.

second, if the hot end was hot, the check the fuses. You probably blew one accidently.

The hot end was hot when I was trying to test the extruder motor initially.

I checked the fuses with a multimeter and they're all fine.

Can you home the towers from the control panel?

I have had this issues with running my printer from a pc and it turned out to be more than one saved printer type on the printer settings. After changing the printer on the pull down menu and putting the correct one back, then the pc would talk to the Rambo again.

Thanks for the suggestion but it's not that either. I can't home the towers, and I only have one printer on the dropdown that I created when I initially set up the machine (except the original "default" but that doesn't do anything either).

I noticed also that when it starts up, the Repetier log has a line saying "SD init fail," that always appears (tested with two different SD cards and with no card at all).

When I send commands from Repetier, they just queue up without going through; Repetier says e.g. "3 Command Waiting" but they never occur.

LED7 (the green LED above the USB port) is on, but that's the only one. The LCD is on but frozen; it displays various default heater temps and says "Killed," and I can't navigate the menus.

I also cleared the EEPROM and uploaded the firmware fresh from Arduino, which didn't crash or throw any errors. But still no dice.

Unplug the USB cable. Turn off power to the printer. Turn printer on again. What does the LCD say? Leave the USB cable unplugged. Can you print from SD card?

Doesn't work - LCD same description as above, just says "Killed" at the bottom, can't get to the menu.

I would try to reflash the firmware. If it is just a firmware problem, that should bring it back to life. If the hardware is cooked, then Arduino IDE may not be able to reflash the controller.

I have re-flashed the firmware using the following steps:

- Clear EEPROM from arduino example script
- Download fresh firmware from Rostock github & change only the machine-specific calibration values in Configuration.h (max_length values, printer_radius, invert_dir values)
- Compile & upload to RAMBo

The upload itself succeeds, but the problem persists. This is the weirdest part, because it *seems* like a firmware error, but flashing the firmware doesn't change anything.

My going theory right now is that some chip is fried in a very local, not-completely-catastrophic way... but I don't know enough about the architecture of the board to know if that makes any sense, and if so where the failure might be.

Any thoughts? Really appreciate the suggestions so far.

HEYO just found the problem -- one of the LCD ribbon connectors had come loose when I was switching the motor controllers around, and it just needed a little shove. Sneaky bugger didn't actually cause the screen to malfunction, but only the SD card reader. Love it when it turns out it's something trivial...

But now I'm back to my original problem of the unresponsive extruder stepper. I'm going to start a new thread for that. Thanks again everyone for the suggestions.

JUST KIDDING I never plugged it back in after I was testing it in the Z axis jack. And now it's mysteriously working again yaaaaaayyyy