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Re: [TCML] Newbe's First Coil
I want to thank everybody who commented on my new Tesla coil. Your
input was very helpful. I thought I may give an update.
Since the initial test I rebuilt the top load buy wrapping the cookie
tin with 4 inch diameter aluminum duct forming a 18 inch wide toroid.
I then taped on a small nail to encourage the sparks to start. This
really didn't much change the length of the streamers but they were
noticeably brighter.
I added a dedicated 8 foot ground rod for the RF side of the circuit.
No real change in performance.
Then I built a 4 segment spark gap out of copper pipe fittings. This
worked noticeably better but got hot and the gap spacing closed up. So
I rebuilt it and added a muffin fan. This worked a lot better, had a
real snappy sound and significantly longer streamer from the top
load... for about 10 seconds. Then the fun stopped! I guess the new
spark gap overstressed the ceramic capacitors and one of them quietly
broke down.
So now I'm in the market for a new capacitor. From what I read a MMC
is the way to go, but I'm kind cheap and it would probability cost as
much as I have in the whole coil so far. Also, even after lots of
reading up, I'm a bit confused about choosing an appropriate value
both in capacity and breakdown voltage. Do I need more then one string
in parallel to handle the current? I purchased another OBIT on Ebay so
I will have 2 parallel identical 10kv 23mA transformers powering it.
I haven't completely ruled out making my own capacitor. The party cup
design looks intriguing.
Is there a down side to going big with the capacitor value with the
thought in mind that I may drive the coil with a some somewhat bigger
power supply in the near future. I have a number of 6-7 kv radio
transmitter plate transformers around here that I may wish to try, so
if I'm buying expensive new parts, I may want to give myself some room
to grow. My thought is that if the capacitor value is a bit larger
then optimum I may have trouble charging it fully with the limited OBIT
power supply, but is this a big liability in performance?
Again, any suggestions are very much appreciated.
Charlie
K3YA
-----Original Message-----
From: cbroring@xxxxxxx
To: tesla@xxxxxxxxxx
Sent: Sun, Jan 31, 2010 1:21 pm
Subject: [TCML] Newbe's First Coil
Hello to the members of this list. For no particular reason I built a
Tesla Coil this winter. Just got it running, more or less. So
(hopefully) here are a couple of photo's of what I put together.
http://img651.imageshack.us/img651/5567/1000420.jpg ;
http://img683.imageshack.us/img683/5931/1000424e.jpg ;
http://img651.imageshack.us/img651/5043/1000425.jpg ;
http://img651.imageshack.us/img651/5164/1000427.jpg ;
The transformer is a 10kv 23mA oil burner trans. Primary is about 12
turns # 14 sold house wire 10" diameter with a couple extra taps
available. Secondary is 1300 turns #27 on 3.5 inch pvc. Spark gap is
2 nails spaced about 5/16" Capacitor is two 6000pF 30kv hokey puck
ceramics, and one shows a slight temperature rise with use. Top load
is a cookie tin and bent pizza pan. The ground is the house wiring
tied in to an extensive ham radio/ lightening ground system.
It really doesn't work that great. I removed a coupe turns and moved
the tap around to get the best coupling I could. I get a ring of 2
inch sparks of the pizza plate. I put a screwdriver on top and get 3-4
inch sparks off that. I haven't tried bringing a grounded probe to the
top load yet. Anyway, I read that the ceramic capacitors are not
really durable and one of mine shows some heating after a minuet or so
of on time to. I think I need to work on that next. I expected a
little more out of it even with the 250 watt power transformer.
I need to figure out how to ground the thing. I need a better
capacitor. I have lots of big transformers and DC power supplies to
play with once I get the coil working a bit better.
Any suggestions are much appreciated.
Charlie
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