Got my alternate speedometer today. Its not the same but pretty much the same pieces slightly rearranged.

My thought is that the speedometer and odometer are no more than a voltage meter essentially calibrated with MPH/volt. So If I remove the speedometer portion I will be able to calibrate the voltage output vs frequency input. Then I will be able to just play with the circuit board until I am successfully able to change components in a way that will effect the voltage output vs frequency input.

 

So If I remove the speedometer portion I will be able to calibrate the voltage output vs frequency input.

Can't you make the previously-discussed measurements/modifications with the speedo portion in place?

 

Can't you make the previously-discussed measurements/modifications with the speedo portion in place?

If its just those few outside resistors yes and that does seam likely. But it is awkward to work with and this is just a cheep speedo to practice on. If I can just learn how to change the output voltage to the speedo by a known percentage, I really wont need the speedo. I may try playing with those 3 resistors or the cap on the outside first. Those appear to be the resistors and caps yourself and Hymie speak of. I going to start with what Hymie suggested in post 6 because it appears similar to what the European version is doing in post #1. Hopefully with each iteration I wont damage anything.