I have an electronic transformer input 220VAC output 12VAC 50W made for use with 12v halogen lights. I connected it to the mains and checked the output voltage as I wasn't sure that the gadget was OK. When I checked the output voltage I got a reading of 7.12v. When I reversed the test probes I received a reading of 9.3 volts. I had connected the output wires of the transformer to cable connectors and had pressed the probes down firmly on the screw heads which were tight on the output wires of the transformer. I repeated this test several times and received the same result. What's the explanation? I want to use the transformer via a bridge to power a series of leds that were originally supplied by a 6v supply. Which way of connecting should I use?