An alternative MC-2100 dashboard replacement circuit
As discussed in the comments of earlier MC-2100 related posts, Terry has been working in parallel to create a circuit capable of generating the variable duty cycle PWM signal that the MC-2100 requires to operate. He’s written up a very thorough summary of his design process (click for the PDF file).
Terry’s circuit uses two 555 timers (or a single 556), two potentiometers (one is a trimmer), and various capacitors and resistors. This is a great way to get the MC-2100 working without the dash panel if you don’t have a comparator on hand.