Dave, if you employ only the power supply, all of the tests are not available.
The capacitance test will not work. It requires an AC signal. R.T.
Mine uses a 7.5 volt 6 amp power supply to which produces DC voltage to the unit on demand, just like a battery would. It’s wired in to the mains coming into the unit so only one external AC plug is required. From the outside, the Merc O Tronic looks as original as the day it was made.
