I have a little circuit board, salvaged from a washing machine, that is a nice multi-output switcher. I'd like to use it in a project, but there's one problem: all the output voltages are negative.
I measured the voltages and traced the circuit. The transformer has four secondary pins; three have diode rectifiers, and one does not; it goes straight to what I think is the "ground" output. All the filter caps for all three outputs have their positive pins connected to that lead too.
The three diodes point in the direction that makes all the outputs negative, too (cathodes to the transformer).
The outputs are -5, -12, and -22 volts; very reasonable for a small supply, except that they are *backwards*.
So my question is, can I just reverse the diodes and capacitors, and swap the two leads that send one of the output voltages to the reference used to control the optically isolated feedback, and have a nice supply with *positive* outputs?
Or is there something about the waveform from the transformer -- or something else -- that would prevent this from working?
Isaac