Your adjustment procedure should work. That it does not may due to either:
- the unit is defective, or
- (more likely) the load resistance is too low for the power supply
Many of these low-cost power supplies do not operate properly into very low load resistances. And our "electrolyte cell" plating tanks are very low, often less than .1 ohm.
What do you have connected for a load when you try this adjustment? When you have it adjusted to 6 amps, what is the voltage?
Voltage for CopyCad plating is usually very low. For your 22 sq-in, I'd guess you'll see .4-.5 volts, maybe less.
If you can get hold of a low-value resistor (1 ohm is ideal) rated 5 watts or more, connect it with both controls turned down. Gradually turn up each control in small increments, see if it will get up to 1 volt and 3 amps.
If so, then the power supply is operating correctly, but you'll need to keep the resistor in series while plating. If you plan to plate at the full 10 amps, you'll need a resistor rated 20 watts or more (bigger is even better).
Sean