Neon Sign Transformer High Voltage Power Supply

I remove the Secondary Circuit Ground Fault Protection (SCGFP) as well as the center tap of a neon sign transformer (NST) in order to use it as a high voltage DC power supply for my Farnsworth fusor. The SCGFP will not allow the fusor shell to be grounded without it cutting power to the primary coil, so the circuit is removed. The center tap only allows half the rated voltage of the transformer while the fusor shell is both grounded and rectified to DC current, so this feature is also removed. The unit is then placed under transformer oil for electrical isolation as well as improved heat dissipation .
Special thanks to Fusor.net and specifically Richard Hull for information regarding the function and limitations of NSTs as well as their wiring with relation to a fusor setup.
Thank you also to @glasslinger for providing your wonderfully detailed video demonstrating the procedure for NST disassembly, and subsequent electrical isolation for high voltage transformers.
Contents:
00:00 - Intro
00:40 - Disassembly and wiring
06:47 - Testing
07:59 - Melting tar and inspection
10:30 - Cleanup and further disassembly
13:46 - Insulation and reassembly
17:25 - Enclosure build
20:37 - Adding transformer oil
22:53 - Power supply explanation
23:53 - Demo

[@joeteejoetee]

By the way, your EXTREMELY EXCELLENT design/cut/tape/fold/glue/drill/tap/seal/wire video is AWESOME ! Liked and Subscribed, duh!

[@dalenassar9152]

NICE VIDEO!!! I have MANY of the old style NST's. I found a way to measure the Max current. JUST USE A CHEAP DMM ON mA SETTING! Just short the NST output across the DMM leads and read the mA's. I depotted a 15kV @ 60mA NST so I could remove some shunts to get more current. I got up to about 70mA. THE CAUTIONS: Use a cheap DMM (that you can risk) at the 200mA AC setting. Make sure all the DMM fuses are good (and higher than the NST current). Make SURE the connections between the meter and NST are tight and secure...I used double connections. If a spark happens, that is the END of the meter. I lost one, since it happened to have a blown fuse inside!! The spark went across the blown fuse...putting many kV's through the meter. THANKS AGAIN!! --dALE

[@simonlaker2139]

Watch out the temperature rating of the magnet wire is rated at 180 deg c. I'm amazed the wire and insulation wasnt damaged in the process. Awesome work.

[@Project.Infinity]

Oh wow good to know. Unless my kiln's temperature calibration is off by 20c or more there must be a hefty safety margin in the temperature rating of the magnetic wire. I'm glad it didn't get destroyed! Thanks for the info.

[@simonlaker2139]

@Project.Infinity its probably because the tar was transferring the heat. Burn out ovens for electric motors run at 365 deg. You have to be careful because you can destroy the electric iron laminations . There generally gas fired with water vaper to keep ignition down

[@ElectromagneticVideos]

Wow - very impressive! I never would have dared melting the tar away. Just subscribed - looking forward to watching more of you videos!

[@Project.Infinity]

Well that's quite flattering coming from someone of your background! Unfortunately though I can't take credit for the idea as I learned about the process from one of glasslinger's videos and decided it was worth trying myself. I look forward to watching more of your videos as well, thank you for watching!

[@ElectromagneticVideos]

@@Project.Infinity Thanks! Well your (and glasslinger's) mechanical skill's put mine to shame! I'm always impressed with people who can do that stuff so nicely. Enjoy my videos! Two recent ones use very similar ignition transformers to your neon transformer that luckily didn't have any safety circuitry and weren't center tapped. Only 10kV though ...

[@sficlassic]

Another video like this is from the channel glasslinger. He used a different path to making HV but the same result.

[@Project.Infinity]

Glasslinger is amazing! Yes, his power supply was quite a bit more robust at around 50kV, but it definitely inspired my build. I actually have a link to glasslinger's channel in the description to make sure to give credit where it's due. Thanks for watching!

[@breezetixhv]

Why remove the center tap? It's supposed to have a center tap to split the output voltage due to insulation. You could simply just not ground it. Also I recommend tilting the tank when pulling vacuum, to make it easier for trapped bubbles to float out of the bottom.

[@Project.Infinity]

True, but leaving the transformer case ungrounded would make it float at high voltage. I was actually using this transformer for some time by grounding the case, and floating my fusor. However doing either is really dangerous in practice as any accidental touch or stray arc from the transformer's case or my fusor could legitimately stop my heart. In order to full wave rectify the transformer's full 15kV AND have my fusor's anode grounded (for safety), I needed to isolate the transformer--So I got rid of the case, center tap, and sunk it in oil. I wanted to replace the tar anyway due to the transformer oil insulating and cooling much better, so I could run it at higher current (after removing some shunts) without it burning out. It was a lot of work but it's still functioning wonderfully after making the mods I demonstrated in the video :)

[@breezetixhv]

@Project.Infinity you could at least leave a centertap on the core. Also you shouldn't even touch anything with live hv to begin with, just don't forget it's live lol

[@Project.Infinity]

@@breezetixhv Haha, yeah forgetting it's live is exactly what I was worried about. With the fusor chamber grounded (acting as the anode after rectifying) I can technically touch it now. I still avoid touching anything though just to be safe. I wonder why I should leave the center tap on the core though if I'm leaving the core ungrounded anyway? Wouldn't that increase the chances of the core arcing to the primary? I figured leaving the core floating lowers the potential for internal arcing.

[@breezetixhv]

@@Project.Infinity Technically, the insulation is double, its on both secondaries so it doesn't really change much. But, there's also balancing issues that you possibly will have. It may sound stupid, but I've heard that it's possible. Just leave it centertapped to the core, if you don't want to ground it, then don't. Just don't touch anything high voltage lol, it's not hard to not forget it. Put a hv icon label on it or something, or an indicator, etc etc. With centertap, the insulations sees half the voltage so it won't arc. Also, honestly you didn't really need to remove the tar from the windings, at least some on the sides, as they're still going to heat up about the same temp, even with oil inside.

[@Project.Infinity]

@@breezetixhv I agree, with it center tapped the insulation will only see half the voltage; One secondary at +-7.5kV, the other at -+7.5kV, referenced to ground through the center tap, but that's only true if the center tap is grounded. If the tap is not grounded the secondary coils act as a single coil instead of two half coils so they reach 15kV above ground, which the stock dielectrics (tar/mica) are less likely to keep from arcing as they were only designed to withstand 7.5kV (esp at higher currents due to my removal of some magnetic shunts). Transformer oil and polyimide have a higher dielectric strength than the tar so it mitigates the risk of arcing. Removing the tar also allowed me to remove some magnetic shunts to increase the current output. That's an interesting point about the balancing issue. Luckily it's functioning really well though so I'll probably leave it alone unless I run into any issues. For real thank you for the suggestions and for checking out my video. Your channel has some pretty awesome content and I'll be sure to follow your stuff!

[@therealprofessor976]

Removing the centre tap isn't the best idea as it's a protective measure. Your transformer might break at some point

[@skungpid]

Yes, very AWESOME!. Some questions though because they seem counter-intuitive to me. Since it worked, I know the answers must be "NO". 1. Didn't the mineral spirits wreck the insulation-varnish on the primary/secondary? 2. Doesn't the transformer oil de-stickify (my word) the Kapton tape over time? 3. Was going to ask about x-ray generation, since you are pulling a vacuum.......but you answered it in the video. Again, very AWESOM! Stay safe.....or at least get extra life insurance, then your wife won't mind so much if you touch something you shouldn't have.

[@Project.Infinity]

Haha, extra life insurance probably wouldn't be a bad idea. It was a risk but indeed the magnetic wire insulation wasn't damaged. It's possible it was either a material that's inert to the mineral spirits or cured well enough that the brief contact wasn't enough to damage it. You're spot on with the Kapton tape. The adhesive didn't stick very well once exposed to the transformer oil. Luckily though the tape is held mechanically as well being sandwiched by the coils and core, holding it pretty securely in place. Everything is still working wonderfully so it must be holding up well enough. Thanks for the comment!