Help with a Casiotone MT-140

So I found this thing in my in-laws basement and lo and behold it has some killer tones (ok, like 3 or 4) - anyway, does anyone know a simple way to mod it so I can control the tremolo? There's a great chorus sound but it's got it's own tremolo and I'd love to be able to speed it up or slow it down. Just thought I'd throw it out there

haha i dont think its possible to mod a keyboard that old, or to find current mods for it