Almost any kind of component can go kerpow like that. (Last one that happened to me was a flat-pack IC on a fairly recent hard disk's circuit board... the odor was positively unreal.) It could of been a voltage regulator IC, transistor, capacitor... I've even seen vaporized resistors and diodes.
If you crack open the power supply it'll probably be obvious what detonated, and if you replace it it'll probably be fine. (Well, possibly not. Sometimes a part will release its magic smoke because something upstream from it got shorted or failed in a way that it's letting far too much current past, so a replacement part will also go *bang*. Thus requiring some more in-depth troubleshooting.)
I'd put a nickel on it being a capacitor, or a regulator that failed because of a *shorted* capacitor. Any Mac II-series box is 20 years old now. (give or take about three years.) Computer collectors who are serious about using their machines rather than just displaying them are going to have to start accepting the fact that some parts don't last forever, and the limiting factors are more strongly correlated with age rather than how much use the machine gets. I wouldn't bet on another IIsi being any less likely to go *BANG*.
If you crack open the power supply it'll probably be obvious what detonated, and if you replace it it'll probably be fine. (Well, possibly not. Sometimes a part will release its magic smoke because something upstream from it got shorted or failed in a way that it's letting far too much current past, so a replacement part will also go *bang*. Thus requiring some more in-depth troubleshooting.)
I'd put a nickel on it being a capacitor, or a regulator that failed because of a *shorted* capacitor. Any Mac II-series box is 20 years old now. (give or take about three years.) Computer collectors who are serious about using their machines rather than just displaying them are going to have to start accepting the fact that some parts don't last forever, and the limiting factors are more strongly correlated with age rather than how much use the machine gets. I wouldn't bet on another IIsi being any less likely to go *BANG*.