[sdiy] multiple dc from a single ac supply

[Ken Stone]

Okay, here's one for you... A tube/semiconductor hybrid module needing +/-
15V plus 6V for heaters and +160 for HT all from a single 12vAC wallwart.
A transformer, and a couple of voltage multipiers are required for that!

>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
>
>
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