The MTI Rotophaser is a rotating tremolo horn speaker system made in Italy in the 1970s. It is similar to the top half of a Leslie cabinet.
These are somewhat uncommon to find and often the footswitch has been lost or damaged.
Since the Rotophaser won’t work without the foot switch and its tangle of cable,
I’ve drawn up some schematics for the MTI Rotophaser footswitch and posted them on this page.
Intended to be driven by an external amplifier, a crossover network allows the Rotophaser to be paired with an external speaker cabinet.
An external footswitch is necessary to operate the unit. It is entirely possible and perhaps preferable to eliminate the footswitch and relocate some or all of the switch functions to the cabinet.
Two separate cables feed the footswitch. One cable distributes power (120vac) through the footswitch to control motor functions (slow, fast, off) and the other controls speaker routing.
Without a schematic, the wiring of the Rotophaser footswitch appears to be rather complex and mysterious.
I’ve drawn up two schematics for the footswitch portion of my MTI Rotophaser, bearing an inspection sticker dated early 1980.
Modified MTI Rotophaser. Images below.
These images show the MTI Rotophaser with the cable and footswitch controls bypassed and relocated. The crossover network was also replaced. Note that with the original cable and footswitch, high voltages were present. Here, the speed control is now operated on the unit itself. To avoid high voltages, a relay for remote switching could be used. Because I didn’t have the proper parts on hand, the resistor/capacitor network was eliminated with no noticeable affect.
Your questions, comments or additions to this brief exploration of the MTI Rotophaser are most welcome.
