Powerbook Duo power supply went up in smoke

I've been trying to nut this out but can't offer very much of a definitive answer.

All I can say is what I DO know.

After the disaster of the PowerBook 5300/190 AC Adapter connector, Apple returned to the old DUO style connector with the PowerBook 1400/ 3400/ G3 Series and the Clamshell iBook. They later shrunk the connector with the white iBooks and PowerBook G4.

When used in the iBook/PowerBookG3 and PowerBook G4, the outer large shell is NOT ground but a small reference voltage, which tells the Mac which AC Adapter is connected. For instance, a 45W adapter on a PowerBook G4 17" cannot charge a battery whilst the Mac is awake. This is done by "sensing" the outer shell's voltage. See this Apple Tech Doc.

Whilst the PowerBook Duo's connector is the same, I'm unable to determine if the voltages are on the same pins. I suspect that the outer shield may actually be ground, which it ISN'T on the later AC Adapters.

The pin in the middle doesn't have anything connected, otherwise it could short to the larger outer casing. Also, on the DUO, there was a method of updating firmware on the dual charging station when connected to the PowerBook DUO via the AC Adapter. Since one of the four or as Apple states five pins on the side is stated as being an ADB bus (Apple Desktop Bus), I suspect that one of the pins on the DUO's AC adapter is an ADB signal - also not used on later AC Adapters. See Page 44 here.

So whilst the voltage may be compatible, (24V 1.04Aamp) the wattage is higher (24V 1.87Amp) which may produce a slightly higher voltage under the lower load, AND the pinout compatibility is questionable.

You may be able to find a 3rd party AC adapter, or a used original AC adapter off eBay. Sounds like your adapter may have had it's capacitors leak or burst, or something terrible!

Just be careful, I know the Duo's port can physically accept an iBook G3 Yo-Yo adapter (and I've used it before on my Duo), but I've never been 100% sure if they were truly compatible.

Good luck!