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Small vttc.

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Arcstarter

Fri Feb 20 2009, 09:38PM

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

I was bored last night, so i decided to make a small vttc. It is not boxed up yet, as i need to scroung up some resistors, and i need the socket and top cap.

Well, this is the first vttc i have made that has sparks about as big or bigger than the secondary. The secondary is 1 inch in diameter, about 5 1/2 inches tall, and wound with wire from a microwave fan. About 30AWG. There is no varnish or anything like that, just wire and the pvc pipe (which could be a toilet paper roll to make it completely free).

The primary was very simple, but looks halfway decent. I got a transparency and cut it to a good width, put it around a 2.5 inch pvc pipe, and wound. The primary wire is just some enameled wire, around 18-20 gauge found from an inductor. It has 7 taps, in one turn increments, with male spade terminals for easy tuning. It uses iirc 24 turns in all, the top 7 being tapped.

Feedback was 28 gauge enameled wire, the same wire as was used on my smaller 4 inch coil that my sstc used. It was 22 iirc turns, around the same former as the primary.

The topload is being experimented with, but i currently have 3. One is a washer (put it on there to mess with, and just left there) which is on the bottom, the next one is that same hard drive metal platter (you guys can never seem to make me get rid of it :D), and the next one is a 3 inch sphere. Breakout point is a 24 gauge uninsulated wire, just kinda poking out.

Ground is mains ground :P.

The tube is the good ol' 811A. I am using one, and i have another one, both got for 24 US dollars. The grid leak cap is a 650pf 20kvdc small doorknob cap that i received quite awhile back from Dr. Spark (Thanks Chris Hooper!), and the resistor is currently 3 small ones paralleled, for 4.8k ohms in all. I have not experimented with this at all. Tank cap is another 650pf 20kvdc doorknob cap.

I have it tuned on the last primary turn, has not been experimented with at all.

This is a good way to make a vttc if you do not have the money, wire, patience, or time to wind a large coil. This one only has around 300-500 turns, the wire came from one microwave fan (looks pretty nice for such a cheap coil BTW) .

Video to come soon.

The inductor that the wire for the primary came from.

The secondary.

The primary up close.

Primary

The rewound MOT for the filament transformer. that pic does not have the secondary on it, and i increased the primary turns for less no-load current and much less heating. Slightly reduces volts per turn, which is about 2/3 a volt per turn now.

Primary off of the former, on the transparency like its meant to be

EDIT: Video.

StevenCaton

Sun Feb 22 2009, 03:27AM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

Hi arcstarter.

I am in the process of making some changes to my dual 811A setup right now. I am adding a cooling fan, and making the wiring neater.

You should take some more time and build your system on a small board or piece of plastic, tidy up the wiring, and get a cooling fan. I find that once I get a coil running, then I can concentrate more on the layout and make the coil more aesthetic overall. (and safer)

Glad to see you have it working well though. The spark look decent for only ONE 811A.

Good luck
Steve Caton

EDIT: I wouldn't recommend that you touch the sparks. I know that touching the sparks is "safe" but thats not why its dangerous. Its dangerous because reaching out to touch the sparks involves a slight risk of accidentally touching something else that IS dangerous. Thats how I think of it. Stay clear of that MOT. Just trying to keep you safe bud.

Arcstarter

Sun Feb 22 2009, 07:09AM

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

SteveC wrote ...

Hi arcstarter.

I am in the process of making some changes to my dual 811A setup right now. I am adding a cooling fan, and making the wiring neater.

You should take some more time and build your system on a small board or piece of plastic, tidy up the wiring, and get a cooling fan. I find that once I get a coil running, then I can concentrate more on the layout and make the coil more aesthetic overall. (and safer)

Glad to see you have it working well though. The spark look decent for only ONE 811A.

Good luck
Steve Caton

EDIT: I wouldn't recommend that you touch the sparks. I know that touching the sparks is "safe" but thats not why its dangerous. Its dangerous because reaching out to touch the sparks involves a slight risk of accidentally touching something else that IS dangerous. Thats how I think of it. Stay clear of that MOT. Just trying to keep you safe bud.

Yup. I am unsafe and i know that. Not a good thing, but i am pretty much a 'hybrid' between a dare-devil and stupid.

I will build this on into a small box, i am sure. I never have because i did not like the idea of having a huge secondary and primary. This one is quite cool and fun though. If i had a matched pair, i would use two 811A's, to cut down on heating and have a longer run time.

This setup was very temporary, and it was just to see how a hf vttc would work. It is about 1-1.5mhz or something without topload, and with one it is somewhere near 800khz i am sure.

I need the grid leak resistors (i only need about 20 watts, so it should be cheap or easy to find), and perhaps other stuff to have it running well. I also need to make a new primary/feedback coil. It will be the same kind due to the cheap materials and lightweight, looks good, and is small, but mine had arcs hit it from the secondary due to it FALLING.

I also would like to find a small filament transformer, as having that huge thing that overheats and pulls tons only to power something with about 24 watts. Also a better 2kv plate transformer, as the MOT heats badly even with no load, it is huge (as big as the sparks, i mean come on), and it weighs more than needed. It is mostly about the size though.

This was started as a little project just as proof of concept that a tiny secondary with a little amount of wire and time can work great. The secondary can be made free with a microwave fan and a former, so i thought maybe it would help noobs. Even when i started this thread it was just a little project. But now i want to make it a permanent setup.

uzzors2k

Sun Feb 22 2009, 07:33PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Your lash-up VTTC looks promising, I would definitely box it up.

Arcstarter

Sun Feb 22 2009, 10:41PM

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

Uzzors wrote ...

Your lash-up VTTC looks promising, I would definitely box it up.

Heh, thanks. This is not the first vttc i made with this tube, i tried it with my 4 inch diameter 16 inch tall secondary, and even WITH tuning, the sparks where no bigger. But i probably will box this one up since it is pretty compact. Does anyone know where i could get a good plate transformer that would not fry? When i turned it on the lights dim a bit, but the 24 gauge wire hooking the mot up is COLD after that run. It might be as small as 26 gauge, actually.

So i will get some new grid leak resistors, and tune, then probably box it up.

Firefox

Mon Feb 23 2009, 12:07AM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

I'm going to a junkyard and an electronics surplus place in two weeks, Arcstarter. I could certainly look for a plate transformer for you. What voltage and power are you looking for?

Arcstarter

Mon Feb 23 2009, 12:29AM

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

Firefox wrote ...

I'm going to a junkyard and an electronics surplus place in two weeks, Arcstarter. I could certainly look for a plate transformer for you. What voltage and power are you looking for?

That would be awesome! :O

I am looking for 2kv just like a MOT, but not as big and heavy and lower power. Maybe about half the size and wattage of a small MOT. About 500 watts should be good, and if it is unlike a MOT and more like a NST and has the shunts, that would be even better.

What would you like in return? I have no money, but if you would prefer it, i can sure make it some how. Also, if you do happen to find one, let me know the shipping price, as that should be easy enough to get, as long as it is 10-20 bucks.

Also, could you look for a small filament transformer? I can find a way to pay for that too. I need 6.3 volts, it could be as high as 6.5 volts if you cannot find the right voltage, and 25.2 watts (4 amps) would be good enough, but something like 50 watts would be best so i could use two tubes if ever needed.

Just PM me with the price you are looking for, or anything that i might have that you would like to trade for.

Thanks!

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