Thanks for your reply. I think a straight forward 0 to 5K potentiometer would do the trick as you say, the Curtis manual explains this clearly. The configuration someone 'botched together' in the photo gives a resistance range of 6.2K to 67K. That probably explains why I get nothing on the pedal until about half way down and then it goes way too fast!!! I live in France (I am English) and this old Melex tipper came from a farm - I expect they just probably tried what was at hand - the potentiometer was actually from Mexico....... So I am waiting for a 5K long shaft pot and will let you know if it works. Stay safe - Mike
