Ok... although there may be some power transformers that might provide for voltage changes via wiring one wire to another different tap, this might not be the case. Remember, a case where an output transformer that selects different taps for different output impedances might not hold true for power transformers.
For power transformers capable of both 120/240 VAC operation, what generally holds true on the input voltage side is that there are two separate primary coils. For 240 volts, both of these primary coils are wired in series - and for 120 volts, these two primary coils need to be wired in parallel. Not the same thing as a tap.
Take a look at this model T schematic - see that both primary windings are in parallel.
http://www.dangpow.com/~sunn/schematics/modelt.gifIt can very easily be converted to 240 operation by separating and twisting the blk/wht and brn together... so that the blk transformer wire is attached to the blk plug wire, and the brn/wht transformer wire is connected to the wht plug wire.
You didn't mention the other colors... but this re-wiring would seem to be much the same as yours - brn/wht transformer wire to the wht plug wire... and (guessing here) blk transformer wire to the blk plug wire?
You said that two of the "taps" are taped. Does this mean that these two taps are connected together? If so, then these two are the "center" wires where the two primary coils are connected together in series... and where they have to be disconnected to put both of the primary coils in parallel for 120 volt operation.
Does this make sense?
