I have been trying to replace a Juki TL2010 sewing machine speed control (foot pedal) with a hand operated variable resistor to no avail. I set up some measurements as shown by the diagram thinking that I could just replace the foot pedal with a hand operated variable resistor (rheostat) but have been unable to control the speed that way. The internal parts of the foot pedal seem to be nothing more than a metal tip tracing over a coated surface. There are no detectable diodes or any active element involved, just resistance. While I can get the machine needle to move when I hit the sweet spot on the rheostat, it only goes a stroke or two and stops. This happens at about 4.05 VDC measured voltage and about 0.4ma and about 60 Kohm. In order to get further motion, I have to increase the resistance to above 100K and then slowly reduce it again, but again I get only a stroke or two. I have tried and tried to find an internal circuit diagram for the sewing machine, but the best I can do is a layout of the circuit board which tells next to nothing about the circuit.
Has anyone dealt with one of these sewing machines/foot control before? It seems like it should be so straightforward, but it is not. See the diagrams of the measurements taken with the sewing machine/foot pedal and the attempted rheostat replacement. Does anyone have an insight into what kind of a circuit this foot pedal could be controlling?
Has anyone dealt with one of these sewing machines/foot control before? It seems like it should be so straightforward, but it is not. See the diagrams of the measurements taken with the sewing machine/foot pedal and the attempted rheostat replacement. Does anyone have an insight into what kind of a circuit this foot pedal could be controlling?