I did this with a colleague when we were training technicians on microwaves back in the 90s. The unit was 800 watt which was standard back then and we wired a long power lead straight to the transformer. This was pre inverter days so the transformer fed the 2000v to the voltage doubler circuit and the 3v magnetron heater.

In our info we were told that microwave power diminishes rapidly as they bounce around the cabinet interior so we anticipated that in our big 80 foot long warehouse with the open microwave at one end and me entering the area with a leak detector at the other I would pick up a small sign of microwaves as I walked in which would increase as I walked towards the microwave. Bear in mind that the leak detector is measuring very low microwave levels so even half scale is not dangerous.

Anyway, we connected everything up and my colleague threw the switch… As the transformer powered up the needle on my detector slammed itself across the scale before I even got into the room.

I yelled “Shut it off” and that was the end of our “Test”!

Update: I’m stunned and flattered at the amount of upvotes that this has received but I’m also a little confused by some of the negative comments, after all, I’m just telling a story that’s relative to the question, I’m not making it out to be anything clever or any sort of scientific test or breakthrough.

Anyway, to those who commented let me add a few lines to put things into context:

I grew up the 70s and 80s and did a lot of dumb stuff back then, mainly because I knew a bit and was curious to know more and couldn’t just google stuff. Friends and I made bombs from stuff gleaned in science lessons, tried attaching rockets on bicycles, played out a Molotov cocktail attack on a disused WW2 bunker and explored drainage tunnels with candles and flashlights.

We also tried turbo charging a Ford escort with 12v vacuum cleaner motors and made an elaborate high voltage window mounted flytraps. I did my apprenticeship in the space and defense industry then moved to Bosch Siemens where I ended up as Technical training manager.

We did this experiment in the late 80s using information and the test equipment that was available to us at the time. Even at that time, over 25 years after the first domestic microwaves came out many people were still worried about microwave radiation and the dangers of ovens leaking. 

I remember around this time being told that a man working for one of the microwave producers (probably Sharp or Panasonic) was so keen to show the safety of microwaves that he actually ran a magnetron in his hand held out at arm’s length. I’d love to know if there was any truth to this story.

Additionally, the early history of the microwave heating effect also wasn’t exactly scientific. The most common story is that its heating effect was stumbled on by accident by a sailor walking on the deck eating a chocolate bar. The bar melted in his hand as he walked across the path of the ship’s radar. Over the following decades, many seagulls also felt the effect and paid the price.

By the way, I am also curious about the similarities between Tesla’s work regarding the relationship between voltage and frequency and transmitting power wirelessly and the power emitted from microwaves which causes eddy currents on the surface of metal objects. Surely there are commonalities between the two?

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I actually tried this.

Back in 1990 or so my mom was gifted a Microwave by our rich eccentric aunt. It was really big very brown and really cool.

Fast forward about 3 years I was cooking something in the Microwave and I noticed something. It appeared that the door has closer sensors built into the Microwave side that were hit by latches in the door. So when the door closed it would register the door was closed by the sensor.

“I wonder what would happen if I pushed on the sensors and tricked the microwave into thinking the door was closed and turned the Microwave on” I said.

I was about 11 or 12 so of course I thought of all the safety requirements. I think that amounted to a couple metal butter knives jammed into the sensors, then I pushed the buttons and hit the start button.

BOOM!

The Microwave made a huge pop and the lights went out. Luckily it was the middle of the day, and there was plenty of light streaming from our picture window to see by. I had heard of circuit breakers and I realized the breaker must have tripped.

I checked and sure enough the breaker was tripped. So I turned it back on. I decided to abandon my experiment before the rest of my family figured out what I was doing. I took out the knives and tried the microwave to make sure all was normal.

I closed the door again turned it on, and. Without any boom, the lights went out. Circuit breaker tripped. I tried again with rising panic, no dice.

I had broken the microwave.

I never said a word. I reset the circuit breaker and when the next person used it they just assumed it broke.

I confessed to my family years later, nobody even remembered exactly what happened.

Don’t try it.