I have two Miller 2050 Plasma cutters and the newer one quit working and gives press alert. When turned on with reg set at 70psi both pwr and ready lite comes on. 2 1/2 seconds later the ready lite goes out and press lite comes on. I have correct press thru reg to solenoid valve. The press switch ohms out closed above 40psi. Since I have 2 machines I swapped the four PC boards.(2 on each side) I also swapped the torch/hose assembly. Any suggestions as what to try next?