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pls Need advice to buy appropriate NST

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Arcstarter

Sat Apr 09 2011, 08:22PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Those are all solid state, and run at a high frequency, which would require high voltage fast diodes, and a bunch of protection to keep the RFI that the Tesla coil will inevitably produce out of the very sensitive 'transformer' and diodes.

For a typical SGTC you need 50-60Hz AC, IE an iron transformer.

PhilGood

Sat Apr 09 2011, 10:04PM

Registered Member #3806 Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259

Arcstarter wrote ...

Those are all solid state, and run at a high frequency, which would require high voltage fast diodes, and a bunch of protection to keep the RFI that the Tesla coil will inevitably produce out of the very sensitive 'transformer' and diodes.

For a typical SGTC you need 50-60Hz AC, IE an iron transformer.

They are not solid state ... look at the sizes and weight (22kgs aka 48Lbs for the 10kV 100mA one)
They either come in resin block (those you can see on pics, FART brand) or in metal casing (SIET brand)

The only few solid state ones they are selling are on this page

Interesting video of SIET's transformers manufacturing here

James

Sun Apr 10 2011, 01:53AM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

Fart brand? LOL

Isn't there a local ebay in your region? Another option is oil burner ignition transformers. I don't know if oil heat was ever common over there but it saw a lot of use in the colder parts of the US.

PhilGood

Sun Apr 10 2011, 07:15PM

Registered Member #3806 Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259

Well, unfortunately it's hard to find anything useful for HV experiments en eBay.fr... seems french ppl are not interested with that stuff... no NST at all , and the very few oil burner ignition xformers I found are solid states ones ...

yeah !!

found some 10/50 used NST's quite cheap (20â‚¬ each)... they are 150 kms from my location, but maybe I'll get them...

If I can't test them, what value (approximative) should I read with an ohm meter on the primary and secondary (just to make sure windings are not cut or burnt) ?

James

Mon Apr 11 2011, 03:49AM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

It varies, but you should see approximately the same resistance from either output to the metal casing, probably a few tens of k, and a few Ohms to a few tens of Ohms between the two input terminals.

PhilGood

Mon Apr 11 2011, 04:13AM

Registered Member #3806 Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259

Thanks James, thats gonna help me

Xray

Mon Apr 11 2011, 05:14AM

Registered Member #3429 Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288

You may be able to find an old NST on an old commercial building. Just drive slowly down the streets along the business district of cities in your general area. You may find an old building that has a broken neon sign attached to it. If you find such a building, find out who owns it and contact them. Tell them that you are learing electronics, and you are looking for old NST's for educational purposes. Ask the owner if he/she no longer is planning on having the old broken sign repaired. If they say no, then ask them if you can remove the old transformer. Also offer to remove the old sign if it happens to be an eye-sore and the owner would rather it just be gone. If they give you permission, then you will need to find out what kind of electrical wiring that you will have to deal with. Obviously, you don't want to electrocute yourself trying to remove an old transformer, and you don't want to cause any damage to the owner's wiring or other electrical components. Some jobs of this type could be very complex and difficult if the sign and transformer are very large. But some jobs will be relatively simple, and my need only to unplug the cord from a wall outlet and remove a few screws!

If you decide to go this route, be very careful not to get into something that's over your head (literally and figurately speaking!). And be very careful when attempting to remove a transformer and/or sign from an unsafe height. If you must climb a ladder or climb on a roof, you are risking many things including your life! So think twice before jumping at what may initially look like an easy job.

I once salvaged a 15KV/30mA NST from a Burger King restaurant. The sign was broken and out-dated, and so the management had no problem with me taking the transformer. The sign was going to be trashed anyways.

Good luck!

PhilGood

Mon Apr 11 2011, 11:21AM

Registered Member #3806 Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259

Thanks Xray for your advices, unfortunately there aren't many old buildings of this kind in my area, land costs a lot there and usually when an old building is no longer used it is quickly demolished to build something new...

Also I currently have some health problems that prevent me from driving, I hope I'll get better in some time ... (I had a polyneuritis six months ago, I still have sequels)

It does not really help in finding MO's or TV's ...

I know I could find an MO or TV each day by touring the city Every night for an hour, but now I have to ask friends to pick them up if they see some..

Anyway, good news !!!

I just called the guy selling x4 Fart 10/50, he still has them and whe had a deal, he will keep them till I can go fetch them...

Fart1010

I took them all for 80â‚¬, so I have like 10/200, should be enough for most of my experiments !

Proud Mary

Mon Apr 11 2011, 11:50AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

PhilGood wrote ...

I took them all for 80â‚¬, so I have like 10/200, should be enough for most of my experiments !

20â‚¬ each is good value for a 5kV-0-5kV 50mA unit , Phil.

On ebay UK, I've seen old British "Tunewell" brand 5kV-0-5kV 30mA NST sell for 100â‚¬. ("Tunewell" made the grey metal box full of black tar type of NST)

Tunewell stopped making 'iron' NSTs about 5 years ago, so supplies in the second hand market are drying up, and prices rising.

PhilGood

Mon Apr 11 2011, 12:50PM

Registered Member #3806 Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259

yes I got lucky on this one, and it is also reasonably close to home. (well 300 km round trip, but it is still worth it)

I've seen many Franceformer NST's on international eBay, some at decent prices. ( according to the brand name, I first thought they were a French brand and I was wondering why I couldn't find any 240v-50Hz

)

Btw I wonder if these models are still in use (the ones with the big insulated terminals comming out of the box, left pic)... cause they would never be allowed in Europe. Here terminals must be protected by a waterproof cover (right pic) :

France10

But I feel that Franceformers really look better for what we use them, with their vintage style big insulated terminals

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