Just for the record....

I did try adopting what I had, which is a switching power supply for laptop rated at 15 volts, 5 amps. I actually got an unexpected behavior. With this supply connected to the lamp, there was no output - most of the time. Few times, after few seconds delay, it would come on but other times, no voltage what-so-ever. If I had the lamp disconnected, the voltage would appear and I could connect the lamp and it will continue to work. When it worked, there were definitely some delay.

From this, I suspect, some of this type of power supplies are more than just a switching regulator that there is some "intelligence" built in. Also, I suspect the start-up current of typical lamps that are significantly higher than "ON" current may also be a factor.

Obviously, this is not suitable for this kind of use.

I'm flying blind here but since OP said "spark" "smoke" and "capacitor showed no obvious sign of problems", I suspect the issue is either the transformer wingdings or a power switch. Oil caps usually fail catastrophically. Bulging out or oil leaking all over the place.