my apprentice has been up to..

[Opcom]

http://yomerswanson.googlepages.com/gigantor

Now I know where all the oil caps from Nortex went.

[N3DRB The Derb]

"scares the neighbors" LOL

[k4kyv]

I have a section of drain pipe like that, made of pyrex glass.  I'd bet it would make a better coil form.

[WBear2GCR]

My friend Frank, back in Throgs Neck NY and In Mt. Vernon NY, in his basement had a really good Tesla coil running. He worked for Spellman High Voltage by the time he made it to the house in Mt. Vernon.

It would throw 8-10ft discharges.
I'm not exaggerating at all.

Must have really messed with the bands when he turned it on... heh. Didn't run it for long periods of time. Just enough to scare the pants off the poor girl(s) that he had brought over for a "demonstration"... 

That was back in about 1970.

The italian landlord of his first apartment (when I met him) said only "...factoria televige..." Don't think he understood what it was - but the neighbors in the adjoining apartment probably didn't like it much...

                   _-_-bear

[Vortex Joe - N3IBX]

You have to give the guys who play with Tesla coils some credit. You have to have a set of callognes to do what they do.

Just for the sake of seeing a large arc jump from point A to point B, and maybe to scare the neighborhood girls. This might not be what I'd do with large plate transformers, inductors, etc, but you gotta respect them for their ingenuity.

[Opcom]

I asked him about that coil today. He could never get it to resonate properly but I think it's worth another try since he's made such a nice big secondary already. Just needs a proper HV transformer and a grid dip meter investigation. It got put away after one of the MW oven transformers in the oil tubs blew up. Have to give him credit for putting them in series and using parallelled toasters for ballast like that. He said today he wants to build a small tube type coil to learn the principles, then revisit the big coil. That's good sense.

[Mike/W8BAC]

You Bet Opcom. Keep up your support and when things don't make sense to him, give just a nudge in the right direction. You have a genius in the making.  Way to go.

Mike

[w4bfs]

sounds like a new zorchmaster ... fun

[WBear2GCR]

Ummm... remind him to fully faraday shield the little coil, and preferably work in a room with something like window screen all around and then grounded for the big coil... otherwise, we'll be hearing it/him all over the bands...

                      _-_-bear

[Ed/KB1HYS]

There are folks who modulate those things (AM of course!!) and the spark discharge works as a great speaker...

Check out Youtube and search on Singing telsa coils... 

There is one fella with a coil that has to be 6' tall...

Can you say STRAP!!!

[Opcom]

Tonuight's fun..
http://www.youtube.com/watch?v=ZVD13c6VB7U
folowed by discussions about rectifiers, mercury vaporization temperature, etc.

[Opcom]

There are folks who modulate those things (AM of course!!) and the spark discharge works as a great speaker...

Check out Youtube and search on Singing telsa coils... 

There is one fella with a coil that has to be 6' tall...

Can you say STRAP!!!

It's funny you mentioned modulating them. He asked me for an 811 and socket a couple weeks ago, and last evening brought over some boxes of oil capacitors, microwave oven transformers, resistors, electic stove elements, the 811 and socket, home-rolled mylar capacitors made with aluminum tape, and something that looked like a tesla coil, except the primary seemed more like a 40M 1KW plate coil.

All this stuff got arranged on the table and clip-leaded together. Nothing was soldered or mounted, all clip leads and separate parts. The 811 would light, the half wave rectifier was making HV, but the thing wouldn't oscillate, he said. Ok, so looking at the directions, the part about the primary needing 40 turns of wire had gotten lost, so a winding was made from some #23 insulated stranded wire and taps put every 5 turns. It oscillated the first time, no idea what frequency but it didn't resonate with the secondary (some 1200 turns of #30). About that time the home made cap across the primary shorted out. So anyway, now we know it works and just needs tuning and probably needs better caps. He says the material was mylar but it looked like plastic to me, I think someone sold him the wrong material. To prevent this kind of thing from blowing out the HV PS, an lectric range element (40 ohms cold) was put in series with the MOT primary. Since it was not done in the lab and it was midnight and I didn't want to drag all that stuff out there at that hour, we used PSUD to simulate the power supply. It would have been about 700VDC with 150V ripple. It ws half wave with a 10H choke input and 5uF capactance. The voltage there is based on his saying the MOT was making 1000VAC, but I think it's wrong, I thought they were about 2KV. The DMM he has was reporting about 500VDC when a 40M resistor was in series with the probe and there was no load on the PS, so I think it was more like 2KV. We were flying crude and rude. I also made a point to show that the 811 should always be left on as a bleeder, since there was no bleeder and he had been using a screwdriver to short the cap after each attempt, and that by using the 811, the screwdriver would be spared so many burn marks. (still use it for safety, just in case a clip lead fell off or something.)

The end is that he wants to do a tube type modulated coil, and wants to start with an 811 coil, and then make a bigger one after the small one is successful. I'm not sure how much modulation (grid or cathode) can be put to an oscillator. The project from which this was ill-conceived is shown in the PDF attachment, and also this is in the form of several pictures on my other site: http://www.montagar.com/~patj/tes3.htm

If you can believe it I scanned this into a 12 MHz 386 over 10 years ago with a black and white hand scanner 3" wide, and then colored in the images using microsoft paintbrush where necessary to make them easier to read. But, how does one amplitude modulate such an oscillator? Only slightly, perhaps..

[W3RSW]

Hey Opmeister,
Where'd'ja get the picture of my Square D box?
Camawwn!

[Opcom]

That's my apprentice's handiwork.

[Opcom]

Here is a pic of Jacob's latest Tesla coil secondary. 6.4" diameter, 2000FT wire, 1222 turns, 24AWG, self resonant at 252KHz. He brought it and the electronics cabinet over, and we checked the secondary there to find out the exact frequency, so that the primary can be set up for it. The unit runs two microwave transformers out of phase into a full wave center tap 12H + 10uF choke input filter to make about 1500VDC. This will be the modulated tesla coil and uses an 811A. Once he gets it oscillating properly, we will find a way to drive the tube and modulate it. Then it will sing. Most people use solid state in ther modulated coils but we agreed to use tubes. No matter what I do I can't seem to badger him to get his ham license!!!!!

[WA1GFZ]

Yes, a couple times my kids asked why I never build a tesla coil and XYL told me I could get paid to demonstrate it at school.
All I say is it would just get me into trouble or worse....

Tom Vu's modulated Jacobs ladder was pretty impressive.

[Fred k2dx]

Brings to mind the great fun I had with a Jacobs Ladder when I was around 13. After I got tired of the 20 KV Jacobs Ladder by itself (a neon sign transformer, lots of current available, welding rods for electrodes) I was inspired to connect a 100' long wire swl antenna to one side of the arc... the fun and games that followed were a riot! This was WAY before cable tv. Even the local gendarmes were driving up and down the streets with their spotlights pointed at the power lines. hehehehe.

[Opcom]

He got it to oscillate intermittently. I keep telling him - more windings on the primary as required to drive the 811, and he keeps telling me the primary needs few turns for high Q and efficiency.

Efficiency hardly matters if the 811 won't oscillate! It has to be set up so that it is driven to class C operation and that means alot of grid drive..

anyway, he hooked a tungar bulb to the top and says it glows pretty when the thing does work. So I say - glow is one thing, 10" sparks are another! I asked for a picture or video of the glowing tungar.

[WA1GFZ]

if you think that Tesla coil is cool you should have seen Tom Vu's first PDM filter doing pullups on voice peaks.

[kb3ouk]

Now I rremember where I saw that article for the Tesla coil using an 811, saw this thread and remember reading about it somewhere, but couldn't remember where.