Lincoln SP170 mig, wire speed issue

[Maxakarudy]

As the title suggests, I have a rather oldish Lincoln 240v mig, the wire speed controller doesn't work, just one speed "fast"
I'm guessing the rheostat is toast, where could I get a replacement & and what test can I do to confirm this is the issue.
TIA

 

[500e]

Should have the value on the back, most likely 10Kohms MultiMeter should show if it is working.
Unsolder 1 wire and connect meter set to ohms ( range all according value) across the 2 contacts turn from one end to other reading should be smooth and vary from 0 ohms to the max shown on pot.
If no value you should get a variation of the reading from 0 to ** if it varies it is unlikely to be that component
Anti clock should be 0