[sdiy] Rhythm Ace FR-2L

[Martin Klang]

hi list,

I'm looking for information on the Bentley/Ace Tone/Hammond Rhythm Ace FR-2L.
Ideally a service manual or schematic!

I've picked up a unit, in very nice condition, and intend to add individual trigger inputs.
Separated outputs would be pretty sweet too, though probably quite tricky seeing how much of the sound generator circuits seem to overlap.

My scope says the sounds are triggered by +6.5v (roughly) impulses. Easy. But the power rails are all negative. How does that work?!
I have tried with straight +5v input triggers and it works ok, I just need to shorten the pulse. But since I don't understand how this works I'm a bit worried about messing up and killing a beautiful vintage machine.

If anyone's got anything useful on this or related devices, let me know!

cheers dears,

/m