They can be connected together but you will loose all isolation from the noisy side of the machine.
jeffie-3 wrote: O.K. GND is different than -5v or -12v
TB1 pin 1 and TB2 pin 8 run to the same terminal and that terminal runs to the negative side of the 5 volt supply.
It is not advisable to wire them together, you can use a separate power supply for the TB1 part, or use a USB cable to power it from a spare usb on the PC, or you can power it from the 5I25/6I25/7I92
tommylight wrote: NC switches should give 12V at the Mesa inputs when not tripped.
Check the wiring.
Yep and also, inputs must be 12V relative to field power GND = TB2 pin 8 when on
O.K. I have 11.74 volts from TB8 pin 1, TB8 pin 2, TB8 pin 3, TB8 pin 4 to TB2 pin 8. Checked the voltage at the switchs and it is 0.