pololu a4988 blown again:S (1 reply)

Well, I've got about 1 hour run time on this 3D printer, and have blown 2 pololus.
First time it happened.... there was lots of wire changes, configuring, testing....
So maybe some static discharge...

Last night I got the printer running again, and got a couple prints off..
A calibration cube, and of course a Yoda.
Happy with the prints (with no real calibration yet)
I shut the printer down for the night...

Well, today I flashed it up to get some calibration done,
only to find out the pololu for the extruder has gone bad... (pulses back and forth and does not fully turn anymore)
Adjusted the voltage.... but nope.... sigh...
So I've ordered a couple new ones, but I'm down again...

I'm wondering if its caused by plugging the 12v power supply in/out? sending a voltage spike?

In the meantime... would you mind pointing out to me what could be tweaked to improve print qualities?
Using Repetier-Host with slicer (0.9.8) with Marlin on a Mendel90.

Thanks!