We use a 10amp/30volt rectifier in our studio which is typically set to 4 volts to salt water etch. We were having intermittent power problems, the unit would power up, cathode and connections were clean, but the circuit was incomplete. We found that not enough of the plastic sheath had been removed so the lead wires weren’t always making a connection.
It’s my understanding that once the voltage limit is set the voltage and amp reading will then fluctuate depending upon the load required. A lower voltage will take longer, but result in a much cleaner etch.
If you haven’t already, consider calling Rio for tech support. They’re always ready to help!