My G540 was working just fine until it decided not to. It doesn't have that much use on it. Here's what is happening:

1. Red "fault" LEDs illuminate when power is turned on.
2. Multimeter probes between pin 10 and 12 show open and closed circuits when the E-stop button is switched. Button is working.
3. Disabling the charge pump doesn't change the results. I tried this with and without the DB25 connected.
4. Screen in Mach 3 always shows "external e-stop requested"
5. Multimeter probes between pin 1 and pin 12 show a small fraction of a volt. (limit switch connected and grounded)
6. Multimeter probes between pin 2 and pin 12 show a small fraction of a volt. (limit switch connected and grounded)
7. Multimeter probes between pin 3 and pin 12 show a small fraction of a volt. (limit switch connected and grounded)
8. Multimeter probes between pin 4 and pin 12 show 48V!!!!!!!!! This is without any wire connected to pin 4 input. Is it supposed to be 48V? Was expecting 5 or 10V?
9. Multimeter probes between other pins show 5V as I expected.
10. Multimeter probes between pin 11 and pin 12 show 48V as expected.

The only thing I recently changed in my setup was adding a .1uF ceramic cap to each of the 4 inputs (pins 1 thru 4) and tying them all to pin 12 ground. I've removed the capacitors since then, but no luck getting back to my original working condition.