In the City of Adventure, we were in a hurry to get results to the lab, and didn’t notice our reactor going critical — until it was too late:


Black blood sprayed over the deck, and thick billowing grey smoke obscured the Tesla Coil as power levels rapidly dropped to zero.     “Should we run?”  Brian asked, through his large NIOSH respirator;  “No” I replied, as I cut power to the Coil.   Shedding our ear-cuffs and UV shields, we assessed the damage.   The magic smoke had been let out.

One 12kV transformer was obviously obliterated, perhaps the other was still salvageable.  I took it to the bench and ran it up, relieved to see it still had spunk, though its girth had noticeably expanded.   Rolling back the events in my head, I realized that we pushed the coil hard for almost an hour at or above rated line voltages.   No wonder..

Rummaging through a shelf of transformers, I found a 15kV, 60ma transformer.    On closer examination, it had a GFI circuit, disqualifying it for use in a Coil.    Well, if we were going to have to replace the transformers, we might as well go with a single unit of higher voltage.   So I yanked the Terry filter to add more MOV’s and headed home, wondering where I was going to get a transformer on short notice since our lab sample containers were only good for a few more days.

Once back at the keyboard, I emailed Alan Majernick at to see if he could get a non-GFI transformer shipped out post-haste, and if I needed to upgrade the MMC bank for the higher voltage (currently running two banks of 16 942C20P15K-F’s).    Within the hour I had a PayPal invoice and the answer of “no need” to add more caps.

Alan is great to work with, and always very fast to answer questions & ship.   Now, it’s the waiting game…   It must be time to build another coil 😉


Ordered on Friday, the new transformer arrived on Monday:


And well-packaged:

Cozy Franceformer

After unpacking the transformer, I had to recalibrate the safety gap on the freshly upgraded Terry filter (12kV to 15kV):

and got the coil back up to complete some time-critical experiments…

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