Neon Transformer Question

Hi All,

I recently came across a very large sum of neon transformers. The input is 277v for the primary, the secondary is kicking out 30 miliamps at 7500v. I have some pictures of the transformer on my website:

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does anybody have any idea of what they are worth?

Thank you, Bob Doran

Reply to
Bob1001
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They are worth something for neon sign desigers. But as you can tell, neon tubes are inefficient and dangerous (7500v). Many display signs are turning to low voltage LEDs. I got some samples of 12v RGB light strips if you want them. They have LEDs every inch or half inch, cascable at any length. At a distant, they are almost as good as neon tubes, and much safer.

Reply to
linnix

Boy are they ugly looking. I have a two in the stock pile, though considerably cleaner. I got them for $10 a pop about 10 years ago, and they were new old stock. They are good for building a Jacob's ladder and can be used as part of a Tesla coil.

The Jacobs ladders takes no effort at all to build. Just add the rods to the output. You might be able to sell them on the net with a cool spark photo.

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Reply to
miso

Pulse them for a pulsed cockroach-waldorf 2MEV accelerator; use industrial fluorescent tubes with drift rings for the pipe...

Reply to
Robert Baer

Their worth is determined by the market. Newer neon signs use high frequency inverters to power the tubes. They are somewhat safer, cost less, weigh less, good power factor and more efficient.

Neon is being supplanted by high frequency luminescence "wire/tubes" and LEDs. What you have may be museum pieces before long.

They'd be worth money to Tesla coil addicts. If they are identical they can be paralleled for more current. The 277 volt input would not be desirable for TC use though.

I paid $40 for a new oil furnace ignition transformer (about 75 watts more than what you have) for my first Tesla coil. Then a year later spent $20 on a new NST that was about twice the power. Later I wound my own transformer from scratch and spent about $100 on magnet wire.

Reply to
default

eBay is as good a pricing index as you'll need. New (not used) are typically going for $30-50 with 120 volt primaries. Used seem to start at about a dollar or so, probably typical sales are around $10. Again,

120 volt primaries. With your 277 volt primary, you'll have some difficulity selling these since the typical hobbiest won't have access to that voltage, and a professional will not take any risk in buying a used transformer.

IMHO, these items have no commercial value, and are worth what ever a scrap yard woudl give you, but you could try listing one on eBay and see if it brings any bids. Just a suggestion: do NOT set a high opening bid, start at 99 cents, and let the bidding tell the story. If you set an unrealistic opening bid, you will just be wasting your time.

Reply to
PeterD

I bought a used but working 15KV, 30 mA, 450 watt, 120 volt input neon transformer for $2 a few years ago. They aren't worth much, pretty much scrap value. Keep in mind that these are constant current transformers which makes them safe for Jacob's ladders and other HV toys. I have a 5kV transformer rated at 1 Amp, 5KVA. That sucker really is dangerous and makes a horrific white arc, no current limit.

Reply to
Bob Eld

I wasn't able to see the whole picture - 3000 x 2400 pixel images don't render very well on an 800 x 600 screen.

Maybe shrink them down to some sane size?

Thanks, Rich

Reply to
Rich Grise

Probably more UV than white - don't ever look at the arc without some kind of UV filter, or even the lens from a weldor's hood.

Have Fun! Rich

Reply to
Rich Grise

He stated 7500V @ >30mA, which I think works out to 225W or better.

I probably would have considered reusing some spare microwave oven transformers for this. (My autistic daughter destroys microwave ovens all too often.) Hmm... thinking about that, there is a microwave oven repair facility a few miles away -- I'll have to inquire to see what they do with those they run across.

Jon

Reply to
Jon Kirwan

Speaking as a hobbyist:

As others have already said, they are worth at least their scrap value (copper does have some market value, for example.) You can test their market value somewhat, without adding any value to them first, by selling a few on ebay (keeping in mind you will have to ship them and they aren't light.) Or you can add value to them before trying to sell them by designing some idea around them and either selling that idea instead (while basically still just selling the raw item) or else selling the completed product as a whole. (You may need to adapt them regarding the 277V input, as others have stated, or else find out what they do with lower input voltages.)

Someone mentioned a jacob's ladder, but I never did find them very interesting until I got up around 20kV, or so. I can't recall getting much under 7-8 kV, but I was using an open-air wire arrangement and it's possible you could do some things to help it out on that score. (At 30kV it warked very nicely.) So I kind of doubt these will work all that well as jacob's ladder supplies without a little work, first. But I could be wrong there.

Jon P.S. Problem with higher voltages, which do make for great ladders, is that you also may wish to worry about x-rays and view the ladder from some distance. A dentist's machine will operate often at around 70kV and produce quite useful levels of hard x-rays. At 7.5kV or less, I wouldn't be nearly as worried but just keep it in mind. (Old TVs were required by the FDA to limit exposures to about 0.5 mRem/hr, but they use accelerating voltages that vary from around 12-15kV for smaller ones to maybe 25kV or more for larger sets. Color TV uses higher voltages [from my experience, anyway] than monochrome, as well.)

Reply to
Jon Kirwan

In Europe the first colour TV receivers had a PD500 power triode as a shunt regulator for the 25 kV EHT.

In the service manuals, there was a warning that the tube should not be operated without the shield due to the X-ray radiation from the PD500 anode.

Paul

Reply to
Paul Keinanen

120 vac input would give about 2500 volts out I'd predict.

I've used older automotive ignition coils for this. Using 12 volt supply,

555 based PWM input, about 10 percent duty cycle and low kHz range.

Yes, all people need to be CAREFUL with any of this, especially the casual usenet reader.

Reply to
bw

Yeah my oil burner transformer is 300 W.

Lots of folks are using MOTs for TC's. Their voltage may be a little low but the power is good. It is probably OK to operate them NST style with two each and a ground to double the voltage. They do require some kind of external current limiting.

I had one of the Lindsay reprints by Holler and Cunningham on building TC's ala 1900's style. They start with how to build an induction coil and I adapted their design to the materials we use today (PVC instead of hard rubber, vinyl insulation instead of gutta percha, enamel magnet wire instead of double cotton covered, etc.) Took a month total and about one week in winding the secondary. It runs over 1 KW

5-7.5 KV (with a tapped primary) when used as a mains HV transformer and produces ~100KV+ as an induction coil (5" sparks)
Reply to
default

I just did a search and, yup, found a nice site on the subject of MOTs (learned a new term, I suppose) and TCs. The page I looked at mostly used four of them and used transformer oil over the whole batch (said that they discovered motor oil was probably worse than using water.)

Interesting. I've been stocking up MOTs here against my wife's mild objection to it. When I tell her I've got this great idea for which I'd like to use them that will send meter-long lightening arcs around my garage, I'm sure that may get a rise out of her. :)

And yes, I'm impressed at all the effort you took and mentioned. A lot of work with good results. Um... would you do it again knowing what you know now about the work involved? ;)

Jon

Reply to
Jon Kirwan

The price and availability can't be beat . . .

I hadn't thought of just floating the cores and packing them in oil. The limiting factor probably is the core to primary insulation.

A great hobby IMO. It's not everyone who can command lightening!

My wife is very indulgent when it comes to my hobbies. From her point of view it keeps me busy, happy, at home, doesn't cost much, and they do make good conversation pieces. The downside: noise, chemical odors, TV interference, clutter, and using kitchen utensils for things they were never intended for.

While the primary TC circuits are deadly, the secondary side is relatively safe. (relatively, since I imagine an arc from the primary coil to the secondary would also impress the mains current on the output)

My stereo speakers took direct hits from the arcs (wood being conductive at the voltages involved) yet the bi-amped mosfet power amp wasn't hurt. A nearby computer - turned off, but still plugged into the same mains supply lost its CMOS settings and eventually a memory module died too. Drywall and studs took multiple hits yet never caught fire.

Once you get in the kilowatt range, the arcs are fat white noisy things that go for several feet looking for a ground - wood or concrete etc is close enough.

Power and voltage (and a top loading cap) determine what the arcs look like. Fat corona streamers, to miniature lightening with lots of forking, to heavy bright white arcs.

Other dangers besides simple electrocution are ozone - they are ozone generators, so you want some ventilation (preferably blowing the stuff out an open window). X-rays - only a concern if you put some vacuum tube on the output terminal. Something like a small evacuated glass bulb is all it takes - small #47 pilot lamps will do it - the glass envelope fluoresces green and it will fog photographic film. Standard incandescent lamps are nitrogen filled and the gas will glow but no X-rays.

An interesting phenomena was I inadvertently made an electret. I coated one coil with epoxy and spun it while it catalyzed to give it a nice even coat with no runs. I powered it up and it stayed "charged" for months afterwards. Later learned that's how electret's are made, a plastic insulator is impressed with voltage while it hardens.

Sure, I'd do it again. I'd make it bigger and better.

I potted mine in paraffin wax, I think oil would be better. I used my pressure cooker as a vacuum impregnator for the four secondary bobbins. The winding was more or less mindless work. I'd wind a layer (1-2 minutes) then paint it with varnish and wait for the varnish to get tacky and put down a layer of paper then wind another (while watching TV or listening to music). I'd guide the wire on from

6" away with just my fingers or use a fingernail to press it against the next turn.

My winding machine was crude, but worked very well. I took a heavy DC motor with a 3/8" shaft and banged a piece of wood on to it. I turned the wood down to a cylinder using a chisel and sandpaper to make a mandrel for the bobbins. The bobbins were PVC conduit cores and sheet Plexiglas for end plates with solvent cement holding it together and epoxy to make it leak proof. I used a low voltage DC supply and variac to set the tension and just guided the wire on. To avoid cutting paper to separate the layers I found some 4" adding machine paper rolls and just used that and built the bobbins to match the width.

Another thing would be to use "pies" instead of bobbins (where the wires have to be hand-laid without overlaps). I found I could cut thin rings out of PVC pipe with the "winding machine" used as a lathe, and cut perfect donuts out of Mylar polyester film using a glass cutter with a pivot against an aluminum plate - perfect for pie winding. Running the wire through a hot melt adhesive bath on the way to the pie would give it some extra insulation. Instead of perfect, close wound, coil bobbins, you end up with many "jumble wound" pies. Spiral rather than cylindrical winding. Should be lots faster.

There's some 13 miles of wire in the secondary and according to the resistance (corrected for temperature) I nailed the length to around

300 feet, from the calculated value. My layers were coming up ~7% short for close wound (wire tables versus a turns counter) so I increased the layers to compensate.

These days I'm still playing with resonance, but trying to build a programmable set of chimes to play music. I'm just starting and haven't settled on a chime/striker yet.

Reply to
default

No disagreement to that last. There are lots of ways to kill yourself (without ever owning a motorcycle, or swimming with sharks, ocean kayaking, or other interesting things)

BUT from my own experience: leaving undeveloped film around the TC: It takes roughly 10KV (with a vacuum tube) and over, to produce X-rays, and at the lower voltages it helps to have a heated cathode to produce "soft" X-rays.

At 100 KV, the technique is a lot less particular. A TC operating at

100KV, just ionizing air, will produce tons of ozone (which can kill you just as dead) but no X-rays. Put any evacuated tube on the top terminal and you get X-rays of some sort. Most of the time it is just enough to fluoresce the glass of the bulb and fog film placed next to it, but put a two element high vacuum diode from an old color TV on the top terminal and you have X-rays in abundance - for fogging film at a distance.

Its my understanding that the vacuum toobe manufacturers eventually started adding lots of lead to the glass formula to decrease X radiation. Older TV's used steel boxes to house the damper diode and rectifier diode.

My conclusion is: you have to want to produce X-rays to do it, but there are lots of ways to kill yourself that don't include ionizing chromosomal damage and a slow death to cancer - like ozone and a slow death to cancer, or instant electrocution.

Play safe

Priorities: Be Safe, Have Fun, Don't Get Caught (in that order)

Reply to
default

As a first-draft hack at your list, I'd insert:

Learn new stuff, ... then your list

Some things cannot be learned well without some risk-taking involved. And some of those things which are exciting and energizing enough to provide enough motivation to get over the hurdles of study or hard work involved in the learning experience also happen to be risky, as well. The balancing act between motivation, risk, and educational rewards is complex, of course, and depends also in part on the maturity of those getting the education and the partners they can find to help mitigate risks in the process without losing sight of what's being learned.

And despite all of the above sometimes exploring new territory is still going to be injurious. Everyone knows about the Curie family example. But basic research isn't always safe, nor should it be. Risks need to be taken at times. It's just that all known sources of risk should be accounted for and balanced with other goals as well as possible. How well that is done will depend on the skills and experience of those involved. And nothing is perfect in that regard, either.

If I were a sign-carrier on this topic, it would read:

Yes! to risk mitigation No! to risk avoidance Learn! Explore! Do!

It was wonderful to read that you used film to test out x-ray generation. Your demarcation of 10kV is roughly consistent with numbers I have in my head from very vague theory and some metals (tungsten, in particular.) I don't know, though, if you went to the trouble of securing film that is uniquely sensitive to x-rays. Did you? (There is pretty good film around, these days. Variations of sensitivity across the surface of xray film is on the order of a few percent, probably well below any hobby level of repeatability.)

By the way, there are some nifty experiments to be performed with x-rays. The usual diffusion equations applied to electrons striking a point in the metal (and here again that infinite resistor grid comes to mind as an image to me) don't work well, partly because it is only valid when the electrons are near enough in speed and dissimilar enough in their direction that they that they all behave very close to the mean case. That isn't the case. The mean free path depends on the span between the eV of the source beam and the excitation energy required/allowed by the K shell of the target atoms. So I think the simplifying rule doesn't work and the actual function needs to be explored, experimentally. Okay. Probably has been. But it would be interesting to do it on as-yet unexplored materials, if any. Or gases like air (which you say doesn't appear to generate xrays at the voltages you've tried.)

There's a world out there to poke at!

Jon

Reply to
Jon Kirwan

If you haven't already, it would help if you set up a web site on your experiences, failures, and successes here.

Jon

Reply to
Jon Kirwan

In , default wrote in part:

Most incandescent lamps with design current less than .2 amp and a few others (such as tubular showcase and refrigerator lamps up to 40 watts and longer 60 watt showcase lamps) have a vacuum. Most others have a mixture of argon and nitrogen, mostly argon.

The visual difference between gas fill and vacuum with a Tesla coil is great. This will allow you to see if any given incandescent lamp has a risk of producing X-rays.

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

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