In order to use jumbo mode you must have parallel port pin 2 configured as the "DIR" (direction) signal, and pin 3 configured as the step signal (as shown in Table 13 in the PMDX-126 User's Manual). Is that how you have pins 2 & 3 configured?
It sounds like you have the "Pin3" step signal configured as "Low Active", though there may be something else going on, so read on...
For Jumbo mode you should have the PMDX-126 DIP switches in one of these two configurations from Table 2 in the PMDX-126 User's Manual:
(a) Config6=open, Config5=closed, Config4=open
(b) Config6=open, Config5=open, Config4=closed
where "closed" is the switch moved or pressed down towards the side closest to the "ConfigX" silkscreen, and "open" is with the switch moved or pressed down towards the side AWAY from the "ConfigX" silkscreen.
*IF* you have Mach3 configured with parallel port pin 2 as the direction signal and pin 3 as the step signal , and *if* you have the step signal configured as active high (a red "X" in the "Low Active" column), here is what you should see:
- With the machine not moving, on J4 the "Pin3" LED should be off and the "Pin2" LED will be either off or on depending on the direction polarity and last direction the motor moved. On J5, the "C" LED should be off (step signal cloned from "pin3" with the same polarity) and the "D" LED should be the opposite of the "Pin2" LED (direction signal cloned from "Pin2" and inverted). For example, if the "Pin2" LED is on, the "C" LED should be off.
- When you jog that axis back and forth you should see the "Pin2" and "D" LEDs change state when you change direction of motion, with the "C" LED always in the opposite state from the "Pin2" LED.
- While you are jogging that axis, depending on the jog speed and ambient light, you may see the "Pin3" and "C" LEDs glowing dimly.
If instead you have the Pin3 step signal configured as "Low Active", you should see:
- With the machine not moving, the J4 "Pin3" LED should be on as should the J5 "C" LED.
- While you are jogging that axis, you *may* be able to see the "Pin3" and "C" LEDs get a little dimmer, and then return to their normal brightness when the motion stops.
Please let me know how you have pins 2 & 3 configured and which (if any) of the above LED behaviors you see. It would also be helpful for you to post your Mach3 XML file here so we can take a look.
Bob