It seems to be locked on the CandCNC hub setting. I'm still quite new at this but I thought the S379 code should override the hub and set Mach to 79V.
Another odd anomaly I am having is sometimes the S10 does not turn off the DTHC at the start? As you can see in the screenshot taken after I ran the first section of the program posted below. Maybe the problems are related?
N0010 (Filename: 8in line.tap)
N0020 (Post processor: DTHC-HYT-TAP_SoftPierce+Marker-rev11J.scpost)
N0030 (Date: 13/03/2016)
N0040 G20 (Units: Inches)
N0050 F1
N0060 G53 G90 G40
N0070 (Part: 8in line)
N0080 (Operation: No Offset, Unnamed Level 1, T5: Fine Cut-Mild-Steel-16ga)
N0090 (DTHC has been disabled in this tool)
N0100(Preset Volts: 79) (Preset AMPS: 40)
N0110 ( Air Pressure Preset: 75)
N0120 ( Soft Pierce : 60 percent )
N0130 (This code for use with Ether-Cut upgrade 12-19-14 or later)
N0140( Suggested Tip Size: 45 ) ( DTHC Delay: 3 sec )
N0150 ( Min Cut Length for DTHC ON : 1 units )
N0160 S900
N0170 S10 (DTHC ON/OFF is run by rules)
N0180 S379 (Preset Volts set to 79 Volts)
N0190 S440
N0200 S875 (Set Air Pressure to 75 PSI)
N0210 S530 (DTHC Delay set to 3 Seconds)
N0220 S711 (DTHCIV tuning set to level 1)
N0230 S701 (Clear S Register)
N0240 M00
N0250(Paused: Check the DTHC Settings Hit RUN to continue)

Hub setting. Note I did change the voltage to 150V from the previous 153V before this screenshot.
