It’s possible to use a modern AC adapter to make a power supply for vintage machines. Sometimes this is desirable, because the modern supply may be more reliable than the old ones. But we have to know how to wire it. Here’s how to find positive and negative DC wires so you can wire the supply up properly when you change its plug.
To find the positive and negative wires, apply power to the AC adapter, set your multimeter to DC, then apply the red and black leads to the output and find a combination that gives you positive voltage. Whichever wire is connected to your multimeter’s red lead is positive, and the one on the black lead is negative or ground.
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