Yes so that's pretty much what I've got except that I assumed that if I connected P1 direct to P3, I would get the maximum output voltage. However P3 doesn't seem to respond to different voltages
I take your point that powering it up with P5 and P4 connected may cause a problem.
I'm puzzled why I get the 90V on the "field" pins and not the "armature" pins, but that's because I don't really understand how motors work. As far as I can tell, the motor only has an armature winding.
However, I cannot do any more on this for next week. Thanks for your help so far