Yep, amazing you're not getting a nice "tingle" from 65 vac - I'd double check those voltages.
If you got your transformer from ratshack, do you have the number of xformer? What type of diode are you using? Yes, a schematic would be GREAT! to determine what you've got. There is no real difference between a "homebrew" and commercial etcher, providing the homebrew is providing the correct voltage. The open circuit voltage should be around 17 to 19 volts, either AC or DC. Also, check to see how much the voltage drops when the pad is down doing the etching. If the xformer is too small, the voltage could be dropping too much
Since the etch is working good on carbon steel, I suspect the etch solution as some of the problem.
Ken H>