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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
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
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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