I did some testing using a 2.5 HP DC treadmill motor. You can run it off of a car battery, a car battery charger, and a 20V DeWalt Lithium battery. A 9V Alcaline battery also works. My DC bench power supply did not work and was overloaded immediately.
I pulled the scrollsaw motor and connected it to a battery with it on the bench. Nothing happened, so it might not have enough power to kickstart the motor, so I gave it a little spin, and off it went. Ray told me about the commutator having a dead spot, so I tested it repeatedly, starting from a slightly different position. It worked flawlessly in all positions I tried.
I remounted the motor in the saw without connecting it to the linkage and plugged it into the controller board. Now it starts, but it makes a buzzing noise that is not there when it is running on the pure DC from a battery. I think this buzzing is caused by voltage fluctuation from the controller. It sounds like 60Hz, so the DC voltage is fluctuating, and there is also a lot of 60Hz ripple riding on the DC. I don't own an oscilloscope, so I can't check this.
I'm going to order a controller board.