I've got a 115V power supply that outputs 12VDC. This unit was pulled from a machine that was built in Japan and it's possible it was custom built for this device. I can't find any identifying information about the power supply, to look up documentation.
I plugged it in and started testing the output side to see what I'd get. There are 4 terminal posts on the DC output. Terminals 2 and 3 are jumpered together -- making me think the configuration is: T1 (+12V), T2 (GND), T3 (GND), T4 (+12V). When I put my multimeter on Terminals 1 & 2 I get 12V. When I put it on 3 & 4 I get -12V. Obviously, reversing the leads on my multimeter makes it +12V.
So the question I've got is: why are 3&4 jumpered together? I would think that would only be done if they were ground. But I only get +12V on the multimeter if I treat terminal post #3 as positive, not ground.