Well, I just managed to smoke my Spindle controller board, a Puma SM. I was trying to add CNC4PC's C6 speed interface card, and missed the bit about using an isolated power supply. The C6 is dead, only putting out a constant 4.48 volts, and the Puma is no better, unresponsive to my old relay board, with the reset LED constantly lit.
I guess I'm in the market for another speed controller, any suggestions? Spindle monitoring and rigid tapping would be great, I'm not against the idea of switching out the 110VDC motor I'm using now, brushless would be nice, as would more horsepower.