I should add that my RANGE switch is ON-ON. I'll try the LFO kill on my breadboard to see what happens.
OK, so I finally got around to trying out the ON-OFF-ON range switch. It kills the LFO and turns the SWEEP control into a manual control, just like on the un-modded Circulator. To me, phasers only sound good when they're moving, so I won't be replacing the ON-ON RANGE switch in my Circulator with an ON-OFF-ON switch.