Guess what this is?

:)

Battery, switch and inverter all correct.

So that's it? No one has any idea?

Tressie.

Trespasser Inscribed thus:

Well its a high voltage generator used for generating a corona discharge from the silver ball !

That would be my guess as well. The foil-covered ball does somewhat resemble the business-end of a Van de Graff generator. Prolly like one of those hippy-dippy things you used to be able to buy back in the 70's ('cos, like, man, negative ions are GOOD for you, y'know, man?) But without knowing what's on the cct board (in between the xfrmr and the ball) it's difficult to say for sure.

Cheers, Pete.

Pete Wilcox Inscribed thus:

Wow man, Wow...

I agree ! I suspect that the large transformer just supplies a lowish voltage, say 50v rectified to feed a neon relaxation oscillator feeding a coil. A bit like a Kettering ignition system. The big silver ball providing a load and producing a corona discharge.

I didn't spot the neons at first look.

tesla coil: ___ / | \ dome \ E / spark E gap E .->

Hi Jasen, Baron and Pete,

The consensus appears to be that the device in the picture is a small Tesla coil. Correct is that induction coil triggering occurs with neon ignition. I think most Tesla coils use a spark gap here. The spark gap in the image is mounted instead across the induction coil output. I'm interested in electric field emissions, and the spark's step function provides an 'all frequencies' impulse. The shiny polystyrene ball has a strange dual function. Like the high voltage plate capacitor which it replaced, it stores charge and increases spark current. Unlike the plate capactitor, it somehow yields a stronger electric field.

I suppose its quite like a miniature Tesla coil, and you were all very clever in getting to that point. The minor differences relate only to the pulsed, as opposed to continuous, high voltage supply. That would have been difficult to determine from any image. Both devices are electric field generators.

Well done.

Tressie.

it'm prepared to call that "close"

ok so it's really a spark gap transmitter and the ball is the capacitance hat antenna. it's still a cool device.,