The hydraulics come on, so raise/lower/tilt work fine but when I throttle forward or reverse, I can hear (and see) the contactors pull in, but the drive motor does little more than an occasional twitch???

Any thoughts? This is an older machine, so no circuit boards, it seems to just have two contactors for fwd and reverse and a big honkin old SCR... and of course the motor. Not a lot to go wrong, I'd think!

Also, anyone know where I could find a manual for this machine? It would be nice to know if I'm putting the right oil in there