Smoked a chip on Extruder board !??

I just completed the firmware installation to my Motherboard and Extruder board. I have the techzone generation 3 electronics with all stepper motors. I hooked up the motherboard / extruder / X motor controller. I started up the reprap software and got the X motor to home and step in both directions. I was able to step the extruder motor as well, so I powered off the unit to test Y and Z.

Next I hooked up Y and Z, changed nothing else. I plugged in the USB cable, then the 12v power cable. As soon as the 12v was connected, my extruder board had a chip smoke up. I checked all my wiring and everything seems correct. The motor was not driving anything and it had just been working, so i'm not sure what happened. I went over things with a multimeter and the voltages are good. Has anyone experienced this?

Here are some photos of the board and the wiring:

[www.flickr.com] Extruder
[www.flickr.com] Burned chip
[www.flickr.com] Motherboard
[www.flickr.com] Both boards

If it's your A3949 that's burned (can't quite see which chip from the photo), those things are notorious for smoking rather easily simply due to how the extruder board is designed. you're better off using a pololu A4983 carrier to drive your extruder stepper, and leave the temp sensing and heating to the extruder board

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Wooden Mendel
Teacup Firmware

The exact same thing happened to me.

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-Nudel
Blog with RepRap Comic

I got almost the same thing when did my board (which worked initially): basically didnt had a motor connected and turned the 10k pot towards its max setting, and turning a test move that burned the top h-bridge - replaced it after and never tried the max setting of the pot again; in retrospect i think it is pretty easy to burn those chips, the hack doesnt seem to be too efficient either, so i made another stepper board to use instead.

After reading a hack about using the extruder controller for heat and temp feedback, but using a 4th techzone stepper controller to run the motor, I decided to give that a try. I ordered a new controller, and a extra stepper motor controller. I'm going to test the boards (everything except the extruder motor driver) when they arrive, then hook up the motor to the extra driver.

Good news is that after I burned the chip, I was still successfully able to test X,Y,Z axis via the software. My day was not a total waste.