One more suggestion besides what beenthere said: Make sure your experiment ground is not connected to the power supply common via earth ground. For example, if you connect the oscilloscope probe ground to your PCB ground, you will, in effect, connect the PCB ground to earth. IF the power supply common is not isolated from earth ground you will short the -12V to ground.
I have an electromagnet in which I am creating a functional test to determine if the unit is working properly. If I drive the unit with 24V it will draw 25-35 mA of current.
What the test does is apply 24VDC to the solenoid then checks a voltage at a certain point on the PCB to determine if that voltage falls within a certain range. If the unit does fall within the proper range the test would sequence to the next step which is to switch from 24VDC to 24VAC at which point a holding force test is performed. I am using 2 LM 311's to create a window comparator and those 311's are driven by a 12v bipolar supply. So my thought was could I use the bipolar supply to drive the 24.
Let me know If anyone has anymore questions or recomendations on anything I should look out for when trying to make this work. I appreciate all the help from everyone electronerd beenthere and adrianN