Neon Transformers and Removing Shunts
IamSmooth, Mon Feb 26 2007, 07:16PMBy removing the shunts I know that one can increase available current. Other than increasing the risk of burning out the secondary is there any disadvantage if one is planning for using these for a TC? What have most of you all done: leave the shunts alone or remove? What were the results (performance and life of the NST)?
Re: Neon Transformers and Removing Shunts
J. Aaron Holmes, Mon Feb 26 2007, 07:42PM
I have heard of folks removing the shunts from NSTs, however NSTs are not built with overload in mind. In fact, "overload" in NST terms is "normal" in TC terms
The NST secondary wires are hair-fine, and may not last for long at much higher than rated current. I don't know that for certain, though. However, as NST are easily gotten for cheap (in the U.S., at least, and probably in many other places), I'd vote for the tried and true method of paralleling multiple NSTs for higher current over prying them open and modifying them. They are generally covered in tar or (worse) epoxy, and so any modification or, more commonly, repair, is usually a messy, time-consuming process. Often best avoided by just tossing the NST out and getting a new one
My 2c.
Regards,
Aaron, N7OE
J. Aaron Holmes, Mon Feb 26 2007, 07:42PM
I have heard of folks removing the shunts from NSTs, however NSTs are not built with overload in mind. In fact, "overload" in NST terms is "normal" in TC terms
The NST secondary wires are hair-fine, and may not last for long at much higher than rated current. I don't know that for certain, though. However, as NST are easily gotten for cheap (in the U.S., at least, and probably in many other places), I'd vote for the tried and true method of paralleling multiple NSTs for higher current over prying them open and modifying them. They are generally covered in tar or (worse) epoxy, and so any modification or, more commonly, repair, is usually a messy, time-consuming process. Often best avoided by just tossing the NST out and getting a new one My 2c.
Regards,
Aaron, N7OE
Re: Neon Transformers and Removing Shunts
Hazmatt_(The Underdog), Tue Feb 27 2007, 02:17AM
Avoid depotting NST's, I've done it 3 times and its a total mess.
Also remenber that depending on the mfgr. you are not guaranteed to have shunt plates in the core. Some mfgr's use a core with the shunt built in with a set air gap. Grinding it down would be a big waste of time because you have 2 shunts per lamination, and close to 200 or more laminations per core.
I'd go parallel with identical NST's as well.
Hazmatt_(The Underdog), Tue Feb 27 2007, 02:17AM
Avoid depotting NST's, I've done it 3 times and its a total mess.
Also remenber that depending on the mfgr. you are not guaranteed to have shunt plates in the core. Some mfgr's use a core with the shunt built in with a set air gap. Grinding it down would be a big waste of time because you have 2 shunts per lamination, and close to 200 or more laminations per core.
I'd go parallel with identical NST's as well.
Re: Neon Transformers and Removing Shunts
sparky, Thu Mar 01 2007, 07:35AM
Shunts are 95% accessible in every NST unit I have seen. I spent years recycling NSTs and its now an easy enough science for me, but I must admit I think going with epoxy potting was a dumb idea. I have 2 15kV 60mA NPF NST units that I turned into 200mA units and paralleled them for more power. These units put out 4kW of pure terror!!
sparky, Thu Mar 01 2007, 07:35AM
Hazmatt_(The Underdog) wrote ...
Avoid depotting NST's, I've done it 3 times and its a total mess.
Also remenber that depending on the mfgr. you are not guaranteed to have shunt plates in the core. Some mfgr's use a core with the shunt built in with a set air gap. Grinding it down would be a big waste of time because you have 2 shunts per lamination, and close to 200 or more laminations per core.
I'd go parallel with identical NST's as well.
Avoid depotting NST's, I've done it 3 times and its a total mess.
Also remenber that depending on the mfgr. you are not guaranteed to have shunt plates in the core. Some mfgr's use a core with the shunt built in with a set air gap. Grinding it down would be a big waste of time because you have 2 shunts per lamination, and close to 200 or more laminations per core.
I'd go parallel with identical NST's as well.
Shunts are 95% accessible in every NST unit I have seen. I spent years recycling NSTs and its now an easy enough science for me, but I must admit I think going with epoxy potting was a dumb idea. I have 2 15kV 60mA NPF NST units that I turned into 200mA units and paralleled them for more power. These units put out 4kW of pure terror!!
Re: Neon Transformers and Removing Shunts
Dr. Slack, Thu Mar 01 2007, 08:32AM
If you want hairy scary transformer current, then you may be better off seriesing 6 MOT secondaries, centre-tapped to ground, with due control of core potential to minimise the possibilties for insulation breakdown, rather than serious remodelling of existing NSTs. I've had such a 12kV 1000mA "NST" running in air without breakdown for a while now, though admittedly have only powered a JL from it, not had it on a TC, so the insulation has not been seriously challenged. It might need dunking in oil for TC use.
Dr. Slack, Thu Mar 01 2007, 08:32AM
If you want hairy scary transformer current, then you may be better off seriesing 6 MOT secondaries, centre-tapped to ground, with due control of core potential to minimise the possibilties for insulation breakdown, rather than serious remodelling of existing NSTs. I've had such a 12kV 1000mA "NST" running in air without breakdown for a while now, though admittedly have only powered a JL from it, not had it on a TC, so the insulation has not been seriously challenged. It might need dunking in oil for TC use.
Re: Neon Transformers and Removing Shunts
cbfull, Thu Mar 01 2007, 05:42PM
I wouldn't mind knowing how you went about converting a 60mA unit to a 200mA unit without melting the secondary. What brand of tranny was it?
I have 4 Magnetek 15/60 units, but with 4 of them I can para them all up to get 240mA so there's really no need to do something like that, but I wouldn't mind boosting them up to 100mA each. I have a big variac that is set up for current limiting service so I would have plenty of control.
Details please!
cbfull, Thu Mar 01 2007, 05:42PM
sparky wrote ...
Shunts are 95% accessible in every NST unit I have seen. I spent years recycling NSTs and its now an easy enough science for me, but I must admit I think going with epoxy potting was a dumb idea. I have 2 15kV 60mA NPF NST units that I turned into 200mA units and paralleled them for more power. These units put out 4kW of pure terror!!
Shunts are 95% accessible in every NST unit I have seen. I spent years recycling NSTs and its now an easy enough science for me, but I must admit I think going with epoxy potting was a dumb idea. I have 2 15kV 60mA NPF NST units that I turned into 200mA units and paralleled them for more power. These units put out 4kW of pure terror!!
I wouldn't mind knowing how you went about converting a 60mA unit to a 200mA unit without melting the secondary. What brand of tranny was it?
I have 4 Magnetek 15/60 units, but with 4 of them I can para them all up to get 240mA so there's really no need to do something like that, but I wouldn't mind boosting them up to 100mA each. I have a big variac that is set up for current limiting service so I would have plenty of control.
Details please!
Re: Neon Transformers and Removing Shunts
sparky, Thu Mar 01 2007, 06:39PM
I have several large cored -older France-former units. Un-potted these NSTs had a large stack of shunts. The primaries were wound with 10AWG - and the secondaries appear to be 26-27 AWG...can't be sure though---. I knocked out a few shunts on either side and ran the NST for a short run on an arc test with the transformers under oil. The secondary current hovered around the 200 mA mark.
These 15kv 60ma unit cores are identical to two cold cathode NST unit I had a while back they were 12 kV 120mA, and one 15kv 120mA - so I guess years ago when metal was cheap france-former used the same core size for all of their units...
sparky, Thu Mar 01 2007, 06:39PM
I have several large cored -older France-former units. Un-potted these NSTs had a large stack of shunts. The primaries were wound with 10AWG - and the secondaries appear to be 26-27 AWG...can't be sure though---. I knocked out a few shunts on either side and ran the NST for a short run on an arc test with the transformers under oil. The secondary current hovered around the 200 mA mark.
These 15kv 60ma unit cores are identical to two cold cathode NST unit I had a while back they were 12 kV 120mA, and one 15kv 120mA - so I guess years ago when metal was cheap france-former used the same core size for all of their units...
Re: Neon Transformers and Removing Shunts
Download, Mon Mar 05 2007, 07:33AM
i saw a 120ma nst over currented to 250ma one nice arcs to
Download, Mon Mar 05 2007, 07:33AM
i saw a 120ma nst over currented to 250ma one nice arcs to
Print this page