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Re: [TCML] Old VDG and Tesla coil found in attic


Definitely a nice couple of finds. You might check old city directories to see who lived in the house in the past. Perhaps you can connect a name to a high school or college year book, if you have time for that sort of historical digging.

I can't help you much on the VDG, but the construction of VTTC looks very much like one that I saw in my seventh grade science class a very long time ago (?1965?), in a galaxy far, far away. Only difference was that the coil that I remember had either two or 4 tubes instead of one. I'm pretty sure that it was built by a teacher, and everyone was afraid to turn it on. As the school year drew to a close, I finally pestered my science teacher enough to get to try it. The tubes lit, but there was no discharge. A huge letdown, after staring longingly at it for nearly a whole year while gagging through my fetal pig dissection. I'd bet that an 811A tube would be a likely candidate, but you should check the plate and filament voltages and pinout of the tube socket for compatibility. You will probably have to replace the Black Beauty caps to get reliable operation. It's interesting that I can't see anything resembling a mica transmitting cap in the bottom photo. You will have to check the construction and your derived schematic to see if the main tank cap is physically missing. It seems unlikely to me that the Black Beauty caps would be sufficient for the tank circuit, but I could be wrong. I think the design came from an ~1935 radio experimenter type magazine. If you have access to Cameron Prince's TC website, where all of Harry Goldman's TCBA newsletters are archived, I'm pretty sure that you will find the schematic, or one much like it, reproduced there.

I personally wouldn't change the secondary geometry. The piece is far more interesting and valuable as an historical artifact than anything more modern that you could supercharge it into. That would be like turning a '37 Chevy pickup into a street rod! If you want really big sparks, then start fresh with a couple of 833Cs, some MOTs, a MMC tank cap, and a 4" x 20" secondary with a 6" toroid. As I read it, the TCML consensus seems to be that VTTCs do not necessarily play by the same design rules as disruptive coils, where a 3.5:1 to 5:1 height/diameter ratio seems to be optimum. Note also that this VTTC doesn't have a toroid, typical for designs of its era, though many current designs do include one. As built, it certainty won't deliver the 15" sword-like sparks of a current design, but it's a nice period piece that would look pretty sharp all cleaned up. After restoration, you might get a nice corona with one or two inch discharges to a grounded conductor, but it should still be able to light up a fluorescent tube at a distance, effectively excite a neon crackle tube, or power a corona spinner. Good luck, and keep us up to date on your progress with the restoration. Not very often that one finds a vintage TC to restore.

Steve date wrote:

Several years ago I found a VDG and Tesla coil in an attic doing an install job near Seattle. I asked the new home owners about the equipment in their attic and they didn't have the slightest knowledge of what the "junk" was. They said I could have it as long as I hauled it out! this was appx 1981 and I have never had a chance to mess with them.

I am now retired and have the time to start the project.

I have placed them on my website:

My questions for the group:

1. anybody recognize either of them? builder? commercial?

2. should I keep the TC "true" (long secondary) when refurbishing it?

3. any ideas on the tube type? schematic? (yes, I can draw it out)

4. what material would be "best" for the belt

I would appreciate any comments from the group that would help restore them to working condition. (I know, I know... the TC will be a very poor performer by today's standards... This is a "for-fun" project).

I suspect these were originally built for classroom use or school science fair use.

Steve - Seattle
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