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Neon sign transformers for Tesla coil

billybob

Active Member
I was wondering if anyone knew where I could find some vintage neon sign transformers preferably 15k volts for cheap $100 or less? Trying to build a Tesla coil and I really don’t want to resort to MOTs.
Thank you
-billybob
 

Externet

Well-Known Member
Spark plug coils and CRT flyback transformers are in similar voltage range for much lower cost. Are they useable for Tesla things ?
 

unclejed613

Well-Known Member
Most Helpful Member
Spark plug coils and CRT flyback transformers are in similar voltage range for much lower cost. Are they useable for Tesla things ?
ignition coils are marginal for tesla coil power supplies, and only the old flybacks from vacuum tube TVs are useful, as the solid state TV FBTs have internal diodes in them and you only get DC out of them. when i was a kid, i didn't have a neon sign transformer, but had an ignition transformer from an old oil fired residential furnace.... if you find anywhere where houses are being demolished to make room for new housing, you might be able to find one for free (assuming the houses were built in the 1950s or 60s) the one i had was rated 10kV @ 100ma... made a fantastic power supply for a tesla coil
 

billybob

Active Member
good to know thanks. :)
 

DerStrom8

Super Moderator
My first two neon sign transformers came from an old neon sign repair shop. I simply called and asked if they had any of the old style NSTs lying around, and sure enough they did. Most neon signs have gone over to the smaller, cheaper switching transformer style, so the old potted transformers are being thrown out. You don't mention your location, but ask around to see if you've got any neon sign shops nearby.

An alternative, which may be slightly more common, is an oil burner ignition transformer. These are used to ignite the fuel oil for boiler furnaces. These are also being switched over to smaller switching types, so there are plenty of old ones to be had. Furthermore, they're much less niche than NSTs so you can go to just about any HVAC company and ask if they've got some old ones. If you play nice, you might just get lucky :)

Cheers,
Matt
 

Reloadron

Well-Known Member
Most Helpful Member
When I was young Scientific American had a article on building a Laser. I got one of these and, it is a wonder I lived through high school.


View attachment 128578

About the same. I bought a beater used one from a neon sign shop for $1.00. Maybe around '62 or '63. That thing looked like yours, it was 15 KV center tapped and could deliver 30 mA. I used Packard 440 ignition wire with it and it's amazing I avoided electrocution. The size of the insulators tells a story.

As to the thread starter? Try a few neon shops but you want a transformer like the above and not one of the newer electronic types.

Ron
 

billybob

Active Member
Its hard to find the older ones, I looked on ebay and found a few but they are not usually 15k and if they are than they are crazy expensive! I also checked places like amazing1.com, Cregslist, Facebook marketplace, and some scetchy websites. I aslo called all the neon sign shops I could find within 50 miles of me, but most said they didn't have any, and if they did they had no use for them and had already gotten rid of them. As for right now Im switching over to MOTs for my SGTC around two to four. I am just worried about the safty of those things, Neon signs will hurt a lot, but have wayyy less of a chance of killing me than MOTs do.
This is a long shot, but if there is any tesla coil enthusiest that are considering selling their neon sign transformers I would be thrilled to negotiate something!
Thank you,
-billybob
 

DerStrom8

Super Moderator
Once again it would be helpful to know roughly where you are located. Also once again, please look into oil burner ignition transformers. They're far safer than MOTs.
 

billybob

Active Member
Once again it would be helpful to know roughly where you are located. Also once again, please look into oil burner ignition transformers. They're far safer than MOTs.
I live in Georga about an hour from atlanta. Ok I will look into those.
 

DerStrom8

Super Moderator
I live in Georga about an hour from atlanta. Ok I will look into those.
Ah, cool! My brother lives down in Powder Springs.
 

billybob

Active Member
Would something like this work?
1608506235348.png
 

DerStrom8

Super Moderator
Would something like this work?
View attachment 128615
That is exactly it, yes. Depending on the size of your coil, shoot for 8+kV. Larger coils will probably require a higher voltage. 10mA would be the absolute minimum, but I'd shoot for at least 20 if at all possible.

Like the NSTs, make sure the OBIT you get is the bulky cube-shaped type and is not labeled "Solid-State". SS transformers operate at too high a frequency and will not charge the capacitor fully between cycles, leading to very poor efficiency and, most likely, a non-working coil. The one in the picture looks good, though I can't make out the label. Output frequency should be either 50 or 60 Hz.
 
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billybob

Active Member
That is exactly it, yes. Depending on the size of your coil, shoot for 8+kV. Larger coils will probably require a higher voltage. 10mA would be the absolute minimum, but I'd shoot for at least 20 if at all possible.

Like the NSTs, make sure the OBIT you get is the bulky cube-shaped type and is not labeled "Solid-State". SS transformers operate at too high a frequency and will not charge the capacitor fully between cycles, leading to very poor efficiency and, most likely, a non-working coil. The one in the picture looks good, though I can't make out the label. Output frequency should be either 50 or 60 Hz.
If these are around the same voltage and amprage as a NST, why are they so much cheaper? I understand there will probably be a slight downscale in performance with the Oil burners, but what if I had four in phase? My tesla coil is around 3 feet (secondary pvc only) if these will work I will be forever thankful!
 

DerStrom8

Super Moderator
If these are around the same voltage and amprage as a NST, why are they so much cheaper? I understand there will probably be a slight downscale in performance with the Oil burners, but what if I had four in phase? My tesla coil is around 3 feet (secondary pvc only) if these will work I will be forever thankful!
There is no downgrade to performance in my experience. They're most likely cheaper because they're more plentiful. You'll have the occasional shop which has a neon sign, but a large number of homes within the same area will have these on oil burners (definitely more prevalent up north though as home heating becomes more of a chore).
 

unclejed613

Well-Known Member
Most Helpful Member
the problem i had with using 60hz HV in the primary circuit on the tesla coils i built was i was pretty much stuck using 60 hz excitation with a two electrode spark gap... now if i were to today build a TC i would use HVDC and a rotary spark gap...not only is the gap self quenching and self cooling, but you can get an audio tone a lot more pleasant sounding than 60hz
 

billybob

Active Member
Ya, I was thinking of going the rotary spark gap route, but figured the variable vacuum spark gap would be easier to build also self quenches, cools and is less costly. I understand your point though about the noise.
 

billybob

Active Member
Alright I bought a 10k volt 23mA oil ignition burner transformer and am on the lookout for another one of the same rating.
 

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