Bill (KT88), Thanks for preforming the test. Correct, no ICs connected from other equipment. Also the safety equipment ground must be lifted from the wall outlet safety equipment ground if used. (Easiest way is to use a plug in ground cheater). // That is the correct way to test for the proper hook up polarity orientation of the primary winding of a power transformer. The reason the piece of equipment must be totally isolated from any other piece (ICs disconnected), of audio equipment is to eliminate any chance of a ground connection. Also for the test if a chassis equipment ground is used the equipment ground must be lifted. The easiest was to accomplish this is to use a ground cheater. (It also should be said the actual thing that is being referenced to is the grounded service neutral conductor back at the main electrical panel where the safety equipment ground is connected to.) // So the identified conductor was connected to the fuse and switch. That just proves back then Scott must not have paid any attention to power cord wiring standards. I do agree the hot should be connected to the fuse and switch side, especially if other equipment will be connected to it using wire ICs. As for the higher leakage of the two that would indicated the proper primary winding orientation hook up is reversed with the AC plug orientation used. As for the Scott I don't know if you would be able to hear a difference if you were to rewire the primary winding leads that connect to the hot and neutral wire that feed it at the lead connections. It may lower the noise floor or not. Only way to know for sure would be to try it. What I will say most, if not all, the Hi_end audio equipment designers/manufactures check every power transformer primary winding for the proper polarity orientation even though a polarity mark may be on one of the leads of the primary winding. So it must make a difference. Time is money.... // I disagree with you whether a difference could be heard or not if the power transformer polarity orientation is hook up correctly or reversed. I do agree with the rest of your statement though. Safety first. I doubt you will find any Hi-End audio equipment made in the last 15 to 20 years has the power primary winding polarity orientation not wired correctly to the neutral and hot conductors. If one was found to be wired incorrect, the correct way is to rewire the leads to the hot and neutral Lines where they connect to the winding leads. Do not reverse the hot and neutral lines that feed the piece of equipment. .