After several emails back and forth with Arturo, I finally have success!
I now have the c11 board working with the KBLC-19M and have full control of spindle speed.
Here's what worked for me (Your Mileage May Vary):
I needed to verify the maximum voltage across Pin 1 and Pin 2 of the KB board. As stated before, I had the KB board wired to a potentiometer. Started out with the KBLC-19M not connected to the c11.
1. With NOTHING but power to the KB board AND manipulating the pot AND checking the voltage across P1 & P2 of the KB board, I read a maximum of 8Vdc. I had the maximum voltage coming out to the c11 board at 10Vdc which may have caused an over-voltage issue and toasted my chip set on the c11.
2. On the c11 board I then set the pot on the analog out to minimum voltage by rotating the pot adjustment screw fully counter-clockwise.
3. Again, WITHOUT the KB board connected to the c11, I powered up the c11.
4. In Mach3, I requested the maximum RPM (M3 S6000 for me) to match with my maximum pulley speed setting (Pulley 1 is at maximum 6000 for me). Measuring the analog output on the c11, I was only able to get the voltage down to 9Vdc. I knew some adjustments were needed in Mach3.
5. Turned the spindle off (M5)
6. In Mach3, under Motor Tuning, I decreased my spindle velocity to 1200 units (it was at 1500 before).
7. Turned the spindle back on & pushed its speed to maximum rpm via Mach3 as in Step 4.
8. I remeasured the voltage out on the c11 and it was then reading 7Vdc.
9. I adjusted the pot on the c11 to read 8Vdc.
10. Turned the spindle off and turned all power off.
11. Disconnected all three potentiometer wires from the KBLC.
12. Connected the P1 from the KBLC to GND (Analog Out) on the c11.
13. Connected the P2 from the KBLC to 10Vdc (Analog Out) on the c11.
14. Said a prayer!
15. Powered everything up - no sparks or flashes!
16. In Mach3, requested various speeds with success.
Hope this helps!