I've had the same problem on 3 different Bridgeport series 1 Mills. The only
way I found to keep them running was to use a fan blowing directly on
them. The Gecko's (all 12) felt warm to the touch not Hot. I soon as I installed a fan they would run all day long. The steppers were sigma's
and superior's running at 5 amps 52 Volts. All three bridgeports are running
fine now. I am converting my own Bridgeport Series 1 right now. I will be
using Gecko 212's and Mach3 software.