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Odd NST circuitry

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Billybobjoe

Tue Aug 01 2006, 07:50PM

Registered Member #396 Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176

I recently bought two 6kv 30ma NST's and when I tried each one out, they only will strike an arc when the power is first turned on. So I opened one up and there seems to be some circuitry before the actual transformer to strike the arc and then maintain it. NSST

Obviously I don't want the striking option so does anyone think it would be worth it to try to cut off the first part and leave only the transformer? I know I have two of them but I still don't want to risk losing one. I wonder if the transformer is still 60hz?

EDIT - hmm, after some Google searching (with the model number) I found another eBay auction that says "The unit has overload protection and will not operate loads over 6 Kilo Volts. The unit has Secondary Ground Fault Protection and will shutdown in the event an output point is grounded or the output is shorted. Power Supply will resume normal operation once the short circuit or ground fault is corrected and the unit is cycled off and on via line plug or pull chain switch. These units are not intended for use on projects such as Jacob's Ladder or Electronic Air-Cleaners/Ozone Generators. They can not be used to produce an arc or generate ozone."

That would explain things a bit so should I go for the modification?

Marko

Tue Aug 01 2006, 07:58PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

WIth all that epoxy I doubt you could help that nst.
You can eventually draw arcs trough secondary ballast, with sacraficingsome output power (it's anyway just 180 watts...)

Sulaiman

Tue Aug 01 2006, 10:29PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I'm not sure but;

I think that what you have there is not a Neon Sign Transformer
(with fault protection electronics)
but (as it says) a Neon Power Supply.
The electronics you see is a part of a high frequency invertor,
the transformer is probably quite small and light made of ferrite.
(a 'normal' neon transformer would weigh several pounds/kilos)

If you damage the electronics the whole thing may not work!

Heavy = Neon Sign Transformer.
Light = Neon Power Supply.

Steve Ward

Tue Aug 01 2006, 11:53PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Yeah, that looks like the newer high frequency transformers. The one i have actually doesnt mind being shorted out, but i ended up using it to light neon tubes anyway :P.

The fact that i see 2 aluminum tabs sticking out of the epoxy instantly makes me think "heatsinks". Its almost certainly a HF transformer.

If it were mine, id be tempted to remove the electronics part and make my own driver. this is assuming that access can be had to both primary winding connections, the ground center tap, and the HV outputs. If any connection gets broken off inside the epoxy, then forget it, its over. You also have to be careful not to drive it too hard, which would destroy the transformer.

Steve Conner

Wed Aug 02 2006, 09:56AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yea, those are definitely electronic high frequency NSTs. I believe they use resonant rise to strike the arc, and have a protection circuit that stops them sitting continuously in strike mode if the tube fails to light, since it would burn out the MOSFETs or destroy the insulation pretty quick.

I had one of these and I ended up throwing away the electronics and building my own driver for the ferrite transformer. I used a H-bridge running off a current limited power supply, and I could strike arcs and make Jacob's ladders etc. I also tried it with the "ZVS flyback driver" circuit that people here are fond of, and that seemed to work great too, although it drew crazy currents when I pulled arcs from the output.

Marko

Wed Aug 02 2006, 01:39PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Steve Conner wrote ...

Yea, those are definitely electronic high frequency NSTs. I believe they use resonant rise to strike the arc, and have a protection circuit that stops them sitting continuously in strike mode if the tube fails to light, since it would burn out the MOSFETs or destroy the insulation pretty quick.

I had one of these and I ended up throwing away the electronics and building my own driver for the ferrite transformer. I used a H-bridge running off a current limited power supply, and I could strike arcs and make Jacob's ladders etc. I also tried it with the "ZVS flyback driver" circuit that people here are fond of, and that seemed to work great too, although it drew crazy currents when I pulled arcs from the output.

I think I saw a schematic for that thing somewhere, and it was simple mosfet half-bridge driving a ferrite transformer.

It had a GDT, driver IC and etc, there could be some protection circuits and etc.
Anyway nothing more special or 1337 than your bridge drive.

Sometimes (i talked about it before) a mazzili-like royer or similar oscillator is used to get sine output, and it's input choke is bucked via mosfet and driver/controller IC.
(usually smaller CCFL drivers)

Self Defenestrate

Wed Aug 02 2006, 01:52PM

Registered Member #87 Joined: Thu Feb 09 2006, 01:36PM
Location: San Jose
Posts: 191

I had an electronic nst a while back, and they're perfect for multipliers. Multipliers don't draw much current, so it would keep your peice in shape. What did you plan to use them for?

Billybobjoe

Wed Aug 02 2006, 03:43PM

Registered Member #396 Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176

I would definitely say that the aluminum things are heatsinks - I can see some sort of components sticking out from them.

I was going to use one for a 30mw HeNe laser I have (with a variac and a capacitor based HV ignition) so I suppose this would still work - but the nice oil immersed full wave rectifier I made from 1n4007's may not be such a good idea.

I was going to use the other for capacitor charging but that doesn't seem like it would work unless I resisted it to be really slow.

Simon Barsinister

Wed Aug 02 2006, 10:31PM

Registered Member #116 Joined: Fri Feb 10 2006, 03:19AM
Location: Erie Pa, USA
Posts: 29

If you need a good 9KV/30ma nst, I have a few and would be happy to send you one for the cost of shipping. I allready gave one to jrz 126 as he only lives across town. PM me if you want one.
p.s. It's nice knowing someone in the sign business!

The stacked ones are the 9/30's

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