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RE: [TCML] Rebirth of one coil and maybe birth of another
Hi Brian.
I have seen a few web pages showing vttc coils utilizing this tube with
pretty good results, comparable to results obtained with an 833c.
They seem to be fairly robust tubes, and the plates are graphite like
the 833c. There's just the added complication of what to do with those
extra connections since it's a pentode rather than a triode like the
833.
Here are some sites I've found.
http://www.sciencezero.org/vasil/teslina/gu81mpage.html
Another in maybe Italian? Didn't try to translate it but google
translator should be able to manage it.
http://tomaslab.jimdo.com/progetti-1/vttc-con-gu81m/
Another in German
http://web367.login-102.hoststar.ch/teslaspulen/vttc-001.htm
http://web367.login-102.hoststar.ch/teslaspulen/vttc-002.htm
Not sure what language this is:
http://experimenty.kvalitne.cz/index.php?stranka=vttc_4
All seem to have good details as far as schematics/photos/construction.
One that I saw once upon a time had some serious output...20" sparks or
better. May have had 2 tubes in a push-pull combo. Not bad for a tube
coil. I believe I saw it on youtube.
One thing I learned about this tube that should be passed on...it has a
false bottom (made of glass or acrylic, can't remember which) where the
terminals come out, and often the connections between the false bottom
and the real tube connections become corroded and don't make contact.
The first time I tested my tube I got nothing...thought I got a bad tube
and was so bummed. I did some research and voila, there it was...details
about this false bottom and the connection issues, and sure enough that
was the cure. The bottom is held in with some metal tabs that can be
pushed out of the way. Then the plate will be loose. You may have to
hold a solder gun on the connections for a few moments to get the wires
loose, but its certainly better to know/do this on the front end, as the
connections will probably fail at some point as manufactured. I'm sure
they could be redone with some cleaning and resoldering. I never ended
up building a vttc, but if I ever get the motivation/courage to do so I
have enough parts hoarded to make 2 or 3.
Good luck with your coils!
Shannon Weinhold
"The world we have created today has problems that cannot be solved by
thinking the way we thought when we created them."
-Einstein
-----Original Message-----
From: Brian Campbell [mailto:delicious.chicken@xxxxxxxxx]
Sent: Friday, August 27, 2010 3:46 PM
To: tesla@xxxxxxxxxx
Subject: [TCML] Rebirth of one coil and maybe birth of another
Hi All,
I've been lurking for a while. I've had my SRSG coil built for a while
now and managed to kill my very odd 22kv 25ma NST that powered it.
Rather than redesigning my MMC and likely my primary coil to match a
more conventional NST, I was thinking about using an MOT power setup.
Likely 2 or 3 MOTs with secondaries in series and a half or full wave
voltage doubler. My first question is if anyone has any relevant advice
on replacing an NST power supply with MOTs. I admit that I haven't spent
any time in JavaTC playing with the numbers. If that's what I need to do
first, I'm good with that.
Just wanted to put this out there and see if anyone has been down this
path and had any sage advice.
Current coil specs as I remember them (I built this coil last year and
killed the NST on New Year's eve, so it's been a while):
Dead NST: 22KV @ 25mA
4" form secondary wound w/ 28AWG to 25"
MMC = series string of 30 CD942 caps, jumpered @19 (I did it this way so
I could support a static gap or SRSG operation) Primary = 25' of .25"
copper tubing with .25" spacing.
My current assumption is that with more power (likely lower voltage but
much higher current) power supply, that this should leave me with extra
caps after rearranging (ugh) my MMC configuration and re-tapping my
primary.
This brings me to my second question: With extra caps left over, I am
considering starting in on a VTTC.
My current 'plan' includes an MOT power supply and a GU81M tube that I
already have.
Question: anyone have any schematics or advice for a VTTC using this
tube? I saw some old discussions and even a couple of photos in the
archive, but not much in the way of discussion of components or
schematics.
Thanks!
-Brian
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