Subject: Coupling test
From: richard.quick-at-slug-dot-org (Richard Quick)
Date: Thu, 13 Jul 1995 20:46:00 GMT
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* Original msg to: Esondrmn-at-aol-dot-com
Quoting Ed Sonderman:
ES> I'm not sure you received this the first time so I am
ES> re-sending it.
I am beginning to wonder about how costly my free internet access
really is. I could go on and on about the mail problems, but the
sysop here scans the mail routinely... Nuf said?
ES> I had four pieces of plastic made 1.0" thick and 8.0" in
ES> dia. I placed all four under the secondary to raise it up
ES> and loosen the coupling. This seems to have eliminated all
ES> the corona problems - I don't see any. I think I did loose
ES> some intensity in the secondary discharges. I will try it
ES> again with only three discs (3.0" elevation). This
ES> shouldn't make it necessary to retune the system - correct?
Loosening the coupling might affect the system tune slightly, but
it will not make a major change. I would expect that your tune
sharpened up a bit, but you should not have to move the primary
tap more than a quarter turn, if at all. Raising the secondary up
four inches is a major change in the coupling, and you may well
find that three inches of elevation is sufficient.
ES> I did notice a new problem and I'm not sure what it is. As
ES> I turn the power up, the gaps start firing and before
ES> breakout I hear a muffled pop sort of noise (my wife calls
ES> it a "poof sound"), kind of like a small muffled explosion.
ES> It sounds like I might have discharges inside the secondary
ES> coil form. It is sealed, the wire never goes inside and
ES> I have a small hole in the center in the botttom plate to
ES> equalize air pressure.
It is unlikely that this secondary is electrically compromised.
Any internal breakdown of a secondary coil usually results in
a complete failure, indicated by burn marks through the coil form
sidewall, smoke (especially from the vent hole if the coil is
vented), arcing between turns, and complete loss of secondary
discharge. If you don't report any of these symptoms then I would
assume that the secondary coil is OK.
ES> Maybe it is comming from the rotary spark gap, it is in a
ES> box which could account for the muffled sound. I also hear
ES> this sound sometimes when I am getting discharges from the
ES> toroid - at full power. I need to find this, it sounds like
ES> something is going to get damaged.
OK, how do you go about tracking a mysterious muffled pop in
high-voltage equipment? Get a length of garden hose or similar
plastic tubing and remove all metal fittings. Place one end of
the tube near a possible source for the sound and listen at the
other end. The tube can be moved around the coil system until the
source of the noise can be better located.
ES> Can we talk about toroid height again? I realize the
ES> correct height for a particular system must be found
ES> empirically. What symptoms would I see if it is too low?
ES> If it is too high?
A toriod that is too low does not throw the spark out laterally
as far as possible. Frequently a low toriod is coupled into the
primary/secondary field flux and acts as a shorted turn. A good
indication of this is when the discharges strike downwards and
frequently lock onto the strike rail instead of leaving the
system sideways. When I set my 10 inch coil up with the 40 inch
toriod at the end of the video tape the toriod was mounted much
too low; more than half of the discharges ended up at the strike
A toriod that is too high does not offer corona protection to the
top turns of the secondary, including the air wound turns from
the top of the coil to the base of the toriod. Symptoms of a high
toroid include excessive corona loss and discharges from the top
turns of the secondary. When I set my 10 inch coil up with the 20
inch toriod (about 2/3 of the way through the video) the toriod
was mounted much too high; full power strikes were originating
from the air wound turns that connected the coil to the toriod
The interesting note is that in both examples from my video the
stand-off insulator was the same. Both toriods were almost
exactly the same height above the top turn of the secondary...
ES> By the way, I am now using a new H.P. VL2 486/66 computer
ES> instead of my old Macintosh. Now I will be able to use all
ES> the DOS utilities that everyone else uses for uuencode and
ES> for GIF files. Also I can read the disc that you sent me.
Hey, do you still have copies of the GIFs that were sent out to
the group awhile back?
... If all else fails... Throw another megavolt across it!
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