[sdiy] multiple dc from a single ac supply

[Lincoln Fong]

While looking inside a broken Alesis Midiverb 3 yesterday I noticed that
from a single 9V ac wallwart (probably no more than 500mA) they had produced
plus/minus 12V dc reg (just for the audio I presume) as well as 5V regulated
driving all the logic and 3X  7 segment LED displays. The highest DC voltage
I measured was nearly 20V unregulated! I guess by voltage doubling and cap
isolation. Why don't people use these methods more often? It seems sensible.

Having said that can anyone point me to a schematic? The power is fine but
all the LEDs/displays are dead and it phuts on the output.

Lincoln