borrow the unit from your friend and measure the voltage. I don't have a schematic (I do have one for the CB-7 but only up to the AC plug but not include the transformer or color head). I have mine in storage but I have measured the voltage before. It's two 24VAC supply plus ground that what I remember. Because it's 2 24VAC supply I did thought I could substitute the transformer with 2 10A 24VDC regulated supply and have a very stable light output.