FYI Linistepper Experience
For anyone out there using a Linistepper controller, I'd like to offer some experience. I highly recommend these, by the way.
Recently, I had noticed my Z-axis motor making some strange noises when it was at rest, but powered. It sounded like static. I used it for several weeks like this thinking that it apparently wasn't a serious problem. I did finally find that it was a problem. Eventually, my Z started missing steps. Of course, this happened after I had walked away and was doing something else. It plunged into the table and ruined a two-sided circuit board that I was trying to isolation route. It had been running flawlessly for a year.
It took me a few hours work and an oscilloscope to find that there were two of the drive transistors (TIP122) that must have been heat damaged. The noise I saw on the scope was only on the outputs of the drive transistors and not from the smaller BC337 transistors. I assume that there was some breakdown going on in the NPN junctions that caused this. A good heat sink and proper thermal compound is a must.
All this to say that once they were replaced, I was up and running again. These are great drivers and I'd recommend them to anyone using unipolar motors. They work great. They really ARE easy to fix. Thanks to Roman and James for these controls.
Chad
My Solsylva machine (my first cnc)
http://www.cnczone.com/forums/showthread.php?t=44336