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Re: [TCML] X-ray transformer wiring help!

Hello Curt,

I'm just amplifying on what others have said and maybe add a little more.

An X-Ray transformer is totally unsuitable for SGTC application. The output voltage is way too high. Considering that the output is 75 to 100 KV, it would cost a fortune to build a capacitor bank with a 2x to 3x margin that could handle that kind of voltage. Since your X-Ray transformer probably has DC output, this would introduce its own complications into the design. DC SGTCs have their own unique design requirements. You would also probably blow out the diodes. Its best to stick with AC as a beginner. You would also need a suitable inductive ballast on the low voltage side to limit the current. 10 to 15 KV is the sweet spot for the primary circuit. The voltage is high enough that a spark gap is easily triggered yet low enough that a capacitor bank of reasonable cost can be built. You should start with a non-GFI NST. Some start with 2 MOTs in series with success but the voltage is so low that spark gap triggering can be problematic. Non-GFI NSTs are still available on E-Bay.

I would also start with a static spark gap with a fan blowing across it to help with quenching. Rotary gaps are fairly complex to build correctly.

It sounds like you are already using JAVATC which is good. You need to thoroughly understand what the JAVATC inputs and outputs are used for. Don't build or buy anything until you understand it, otherwise you may be wasting money. There are several excellent web sites that can educate you about Tesla coil design and construction. Here are two good examples:


When I first started with the HV hobby about 25 years ago I knew almost nothing about Tesla coils. I spent about 3 months just reading the TCML archives and studying web sites such as the examples I just referenced. I then used a design program to try out different ideas before I zeroed in on a final design.

Steve White
Cedar Rapids, Iowa

----- Original Message -----
From: "Curt Wilson" <3wisenconst@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, February 21, 2021 7:00:30 PM
Subject: Re: [TCML] X-ray transformer wiring help!

I really appreciate the input. And the safety reminder. I don't mean to
make it sound glorified by any means more a reminisce of battle wounds
survived. I've been running around roofs and climbing trees with nothing
attached to my safety belt but a running chainsaw but since have become a
union carpenter in Boston then gone rogue again but I took advantage of the
available certs, got Osha 10 and 30, fall protection,  Ariel lift...and so
on so I know how to think ahead and be mindful of not only myself but my
surroundings and others aswell I pick and choose the chances I take and
occasionally get reminded that complacency with anything electrical is
unacceptable. Just like I check my footings twice climbing in and out of
the back of my truck these days nevermind up on a roof. Never forget the
main thing that stuck out to me from my Osha 30 class was the last day we
finished the course material and test with like 3 hours to spare and the
instructor started showing us you tube accident videos like the big blue
crane crash but the main one I remember was four Japanese or Chinese
painters at an industrial plant rolling what looked to be a 20 or 30 foot
high work platform one on each leg of it and didn't see the high voltage
lines they were about to roll it into on surveillance camera you saw arcs
and sparks from above the staging rolled a bit further as one painter
luckily fell off the other three went limp and dragged there feet as there
hands stayed Locked tight in place the smoke started appearing from
different parts of there bodies and one caught on fire the one that fell
off managed to get uo after a couole of minutes and trys to get away only
to come back and try to help the other guys and got electrocuted again and
managed to live again the other three passed. Anyone wanting a reality
check ill see if I can find the link and post it. You wouldn't need to warn
further after watching that! I even installed surveillance cameras outside
my hobby shop so I can monitor the area where my earth grounds are driven
into the ground.  (I have kids and take no chances of them getting hurt)
and my shops an 8.5 x 20 car trailer  that's locked up tight when not in
use and I shut down all breakers and short all caps as an extra just incase.
  But back to the coil .it is definitely out of tune. I've be having a hard
enough time getting anything to stay running long enough to be able to tune
it. I did use recycled transformer magnet wire that also has  multiple
pieces soldered together to get the recommended turns according to what I
could understand of the javatc Calc I was trying to use I know that alone
could cause it not to tune properly  but I've unwound multiple transformers
and wound three different size coils one on 4.5inch outside diam. Pvc wound
19" high and the other one I bounce back and forth too is 2 in outside
diam. PVC wound 23" high. And I have 2 primaries as well one is 1/8 "
x9/16" solid copper ribbon layer in 7 coils with 1" spacing on them and the
other is copper 1/4" tubing  thay is similar. Im not sure if I used the
autotune in Java correctly or if I understood it correctly.  But everytime
I started getting it all worked out I'd fry what ever transformer I was
using and have to start all the calculations over again with the new
transformers.  Right now I'm waiting on 504' of 24 Guage magnet wire to
come to wrap a piece of 3.5" pvc up to 40 inches with new wire nice and

On Sun, Feb 21, 2021, 7:12 PM Chris Reeland <chrisreeland@xxxxxxxxx> wrote:

> Hello Curt,
> First, I want to say, (which you might know is coming) from what you have
> said so far, is "Sir, you are going to run out of lives eventually and
> leave your little angel". You must respect voltages at ALL levels. Again
> ALL levels. This is not about "tickles and bites". Please think and learn.
> Even 120VAC in right conditions will take you OUT.
> Please also never touch output of spark gap TC's. Even with objects you
> think are good insulators, no matter how long.
> That said, I am not much of a spark gap TC fella, especially rotary gap
> type. Looks like you have an asynchronous type, which from what I
> understand, needs to have a certain "sweet spot" speed to be optimum.
> As Jim said, yes will not be able to turn up variac much with x-ray
> transformer.
> Yes, your x-ray transformer is rectified and filtered DC.
> Did you follow any kind of plans or formulas for your primary and
> secondary? Or did you just coble from available stuff around and just put
> together with no regard to what is required? What is the capacitance of
> your bucket cap? What is the capacitor actually in there? Need all kinds of
> details here. This is just a few of many asked here right now.
> I would say everything is greatly out of tune in several areas.
> Okay, maybe some others will chime in here more knowledgeable on RSGTC's
> than me. As I am mostly a vacuum tube coil guy so far.
> Chris Reeland
> Ladd Illinois USA
> Sent from my Samsung Galaxy Tab® S
> On Sun, Feb 21, 2021, 4:52 PM Curt Wilson <3wisenconst@xxxxxxxxx> wrote:
> > I beleive it is an 80kv xray transformer. I'm not positive if it has
> > rectifiers or not I beleive it probably does. I will add a link to photos
> > of the inside of the transformer. It did not come with the case or the
> high
> > voltage cables which come to find are quite expensive So i had to find a
> > case that would work, which didn't and started leaking oil all over my
> > hobby shop. So I pulled it out and lined it with rubber roofing and
> > refilled it and temporary am using bare solid 6 Guage copper wire stuck
> in
> > the recieving plug to make my connection too.i know it's no where near
> any
> > kind of safety  standard yet but it's in maternity things up a and
> > upgrading as money allows in the mean time I've been tinkering for over a
> > month and can light a florescent 48" tube up from 3' away just from my
> > primary and the only spark I've gotten from my previous design was about
> an
> > inch coaxed from the toroidal by me with a pair of insulated electricians
> > pliers that was a one and done mistake. The 5000volt insulation rating on
> > the pliers was no match even for my not quite there yet tesla. I'm a
> > builder and welder by trade and so have been wacked with 120 all the time
> > 250 from the live side of my switch on my tombstone 200 amp stic welder
> and
> > 480 3 phase messing around in the control panel of my 4 head woodmizer
> > resaw. 120 and 240 tickle 480 instantly melted the screwdriver handle to
> my
> > hand and shot the rest of the screwdriver about 8 feet behind me and
> stuck
> > it Into the cinderblock wall behind be which gave me a new appreciation
> for
> > the term "tag and lock out" and I even had a bare hv feed from to mots in
> > series jump from the wood I was fractaling and land right on my arm and
> > none of them compared to the bite of that coil through the pliers! I'm
> well
> > aware of the dangers of hv and I also have more lives than the pets from
> > the movie pet cemetery and acknowledge my guardian angel with a tattoo of
> > her on my arm! But I apologize im rambling. In some of the pictures I
> show
> > some of my available electronics items I have at my disposal.  I have
> huge
> > plastic totes of old transformers and chokes resistors all kinds of fuses
> > amd diodes, capacitors,  wire wound resistors and gateways and heat sinks
> > that friends have donated to my fascination and curiosity of electricity
> > and would be more than happy to share with anyone who may need any of the
> > items I have. All I ask is that you pay your own shipping. I have more
> than
> > I can even imagine using.
> > Here's the link to my photos, lemme know if there's any issues opening
> > them. Amd thank you all again for the help with this build .
> > https://photos.app.goo.gl/h4Mr2zVLm2yzxaKy9
> >
> > On Sun, Feb 21, 2021, 3:29 PM Lux, Jim <jim@xxxxxxxxxxxxx> wrote:
> >
> > > On 2/20/21 3:50 PM, Curt Wilson wrote:
> > > > My names Curt and I've been trying to get a tesla coil up and running
> > > for a
> > > > while now. I've used multiple power supplys such as four mots wired
> in
> > > > series parralell with a center tap ground but they did not last
> > probably
> > > > due to being used for fractal wood burning prior. I have tried NST's
> > but
> > > > they had the gcfi on them and only worked for the first few minutes.
> So
> > > now
> > > > I've moved onto a cathode/anode 80 kva x-ray transformer that feeds
> > > through
> > > > a bucket capacitor and into a bench grinder with a 6inch plastic fan
> > > wheel
> > > > that I wove solid copper wire through four of the fins and have a oil
> > > > burner point on with side for the pick ups. My primary coil is 9/16"
> x
> > > 1/8"
> > > > solid copper ribbon with 1"spacing between coils and my current
> > secondary
> > > > is 4.5" pvc with two recycled 34 guage magnet wire soldered together
> > and
> > > my
> > > > top load is two old chevy hubcaps hot glued together. I'm running a
> > 30amp
> > > > variac 125v ac to regulated 125v ac and I can't get past about 30v
> with
> > > out
> > > > the fuse blowing. Just when the rotary gap starts to fire the fuse
> > blows.
> > > > I've tried a mot with secondary shorted between the transformer and
> the
> > > > variac but it didn't seem to make a difference and I've tried a250
> watt
> > > > 15ohm resistor first where the mot was then tried it between the
> > > > transformer and the primary. Both places it just heated up and would
> > not
> > > > allow any spark at the gap. Any help with the wiring on the
> transformer
> > > or
> > > > variac or suggestions would be greatly appreciated! Thanks in
> advance.
> > > > https://photos.app.goo.gl/nPS9fMg36375yAXi8
> > > > _______________________________________________
> > > > Tesla mailing list
> > > > Tesla@xxxxxxxxxxxxxxxxxx
> > > > https://www.pupman.com/mailman/listinfo/tesla
> > > >
> > >
> > > What is your X-ray transformer output voltage?  Most Xray transformers
> > > have *very* high output voltage compared to what's practical for most
> > > home built TCs.
> > >
> > > Xray - 75-120kV isn't unusual.  Neon Sign Transformer (NST) or Pole
> > > Transformer are 12-15 kV.
> > >
> > >
> > > So you should be looking at feeding your Xray with around 10-20VAC.
> > >
> > > A real issue is that Xray transformers don't have any current limiting,
> > > so you'll need a ballast to limit the current (just like pole-pig
> > designs).
> > >
> > > Does your Xray transformer have rectifiers?
> > >
> > >
> > > _______________________________________________
> > > Tesla mailing list
> > > Tesla@xxxxxxxxxxxxxxxxxx
> > > https://www.pupman.com/mailman/listinfo/tesla
> > >
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxxxxxxxxxx
> > https://www.pupman.com/mailman/listinfo/tesla
> >
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