I am not sure why but in post 41
"its possible to connect the 3 wires that originally connected to the C11G PWM to analogue converter"
should of read -
its possible to connect the 3 wires that originally connected to the FC250 speed control potentiometer terminals P1 , P2 & P3 to the C11G PWM to analogue converter
provided the current taken by the C11G PWM to analogue converter is low enough
the speed control terminal P1 can supply the +12V to the C11G
with a FC250J / 230V board like this
or the 110V version
when the speed control potentiometer is fully anti clockwise (counter clockwise )
the DC voltage from the speed control potentiometer terminal P2 may not turn down to zero with respect to terminal P3
Also the maximum voltage when the potentiometer is fully clockwise may not be exactly 12V
as you would expect with a 12V zenner diode regulating the 12V supply !
what is the maximum and minimum speeds displayed by mach 3 and your tachometer ?
John
PS
in mach you can adjust the pulley ratio to change the speed mach 3 displays without changing the actual motor speed