Experiment gone wrong

Almost two years ago, I was performing an experiment. The goal was to use a transformer and a variac to achieve a visible electric arc. I also used a digital multimeter to measure the voltage (with a maximum AC voltage rating of 750v).

So, the plan was to connect the output of the variac to the secondary coil of the step-down transformer (which made it function as a step-up transformer); its primary coil terminals was the output of the system and was hooked-up to the multimeter.

According to the plan, I used the variac to increase the voltage from 0v to 240v which was further multiplied 20 times using the transformer and whose output was measured using the multimeter. Since the max. AC voltage rating was 750v, I thought it could very easily tolerate upto 650v after which I would have disconnected the multimeter from the whole system. And continue raising the voltage.

I was nervous and excited at the same time. I flicked the switch and started the experiment. Everything was normal as planned, no smokes, no fire. The reading in the multimeter was almost 0v. Then I started rotating the knob of the variac really slowly. The voltage reading increased and a very faint humming sound was audible from the transformer (no surprises there too). I cotinued this until I reached 400v; at this point I started checking for any excess heat in the transformer. Fortunately, everything was nice and cool. The multimeter was doing fine too. But the humming sound from the transformer increased drastically and was making me sweat.

Just for the sake of fun, I connected some resistors and electrolytic capacitors to the output; It was very satisfying seeing them blow up.   😂

I started rotating the knob again, everything was doing fine until the voltage reached 580v; I heard sparks from inside the multimeter, I could also smell smoke coming out of the thing. It scared the shit out of me. I flicked the mains switch and the sparks went off. But it was too late. I knew my cute little multimeter had died. But I still opened up the multimeter to see if there is any hope and it turned out that there wasn't any. It was all fried

Ergo, the experiment ended in catastrophe. The consequence was me crying in front of my parents to buy me a new multimeter.

Conclusion : Never take the power ratings of a cheap multimeter for granted.