Has anyone experimented with pololu part # 2128 which is the "black edition" of the same A4988 stepper driver, with purportedly better thermal dissipation and higher current output?

I'm not sure what the root cause of my stepper driver failure was, but if it's a thermal issue I'd be interested to know if these are a viable alternative moving forward.

it could be. These stepper drivers are being run at about 90% of their rated capacity.

http://www.soliforum.com/topic/459/soli … iciencies/

I'm not sure what the root cause of my stepper driver failure was, but if it's a thermal issue I'd be interested to know if these are a viable alternative moving forward.

elmoret - swapped X and Extruder driver chips (as extruder was easier to access on the breakout boards) and my X axis came back to life. Thanks for the suggestion.

Contacted SD support and they're going to send me a replacement ASAP. 

Thanks for the suggestions and thanks to SD support for the prompt replies and service.

My X axis motor drive stopped working mid-print. All remaining axes (Y,Z,E) and heaters are working fine.

Can't move X axis under manual control in RH or Pronterface. During prints, all other axes respond. During homing, SD3 just waits for a few seconds, times out, and continues on with homing other axes. I don't get any sort of error telling me it was expecting and end stop to be hit but it wasn't.

Swapping Z and X motor cables lets me move X axis motor under manual control of Z axis. Motion along whole X axis is fine, and the motor responds properly when sending Z axis commands. So I believe that rules out motor / wiring failure. Z axis motor doesn't respond when plugged into X axis port (can't test with Y cable without over-straining the wire @ the connector).

I tried letting the SD3 sit for some time to let the drivers cool (not that they or the motor were feeling particularly hot, but it was worth a shot). No luck.

I don't have an oscilloscope so I can't trace the outputs of the X motor terminals. But as far as I can tell, the X axis stepper driver is no longer functional.

Can anyone suggest further actions I can take? I've contacted support but I'm hoping the community at large might suggest something short of replacing the X pololu board or the whole motherboard.

I've worked with steppers in university so I have a pretty good idea of how they're supposed to work, but I lack the proper tools at home to diagnose this any further. I  have a multimeter so I can check for shorts and voltage levels, but that's about it. I also have duct tape, string, chewing gum, hand tools, and a modestly stocked bar, for anyone who wants to throw a mcgyver suggestion in there

Thanks in advance