RE: [TCML] ANother tube coil question

["James" <mustang3@xxxxxxx>]

The primary coil is #10 house wire on my big VTTC. The wire gets pretty
hot. However the insulation doesn't smoke. I don't think it matters
much. My coil pulls about 75 amps at 250 volts input. I use a full-wave
bridge to put lots of power into the tube. The half-wave doubler only
fires 60cps. This gives 50% duty cycle. Gives the tube a chance to cool.
Maybe even gives a longer spark. You are running your 833 at (about)
8KV; I'm surprised that you don't get flashover inside the tube. I
zapped a couple like that. That's when I switched to 5868's. Carbon
anode, concentric tube elements make 5868 very tough. James


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of David Rieben
Sent: Wednesday, September 10, 2008 9:27 PM
To: Tesla list
Subject: [TCML] ANother tube coil question

Hi all,

I have been having a bit of trouble lately getting my
VTTC back up and staying running. I flashed over the 
primary to the secondary coil yesterday and damaged 
the secondary enough that I am just going to have to
wind another one. I tried to rewind with #22 wire that 
I already had laying around on a longer form but it still
turned up being WAY out of tune as the original se-
condary was about #26 or possibly #28. I tried winding 
some old #28 or possibly #30 from an old secondary 
bobbing from a dismantled x-ray transformer, but it was 
unusable for rewinding as it had a bunch of glue and 
kraft paper stuck to the wire which caused it to wind 
poorly and to snag and break easily. So it looks like I'll 
be having to either buy some more #28 magnet wire or 
else just buy a prewound secondary coil of the same
approximate demensions and wire guage, as they ap-
pear fairly plentiful on eBay.

Now my question is do you other vacuum tube coilers 
have trouble with your primary coils getting really hot
after just a minute or two of operation? I was originally
using #10 for my primary but it was getting practically 
smoking hot and I ended up replacing it with #6. The 
#6 still gets quite warm after a minute or so of firing,
especially in continuous mode. I'm wondering if it's
more inductive heating going on here than resistive
heating as the leads to the primary coil are of the 
ame guage but don't seem to get near as hot.
My VTTC is ran off of (2) sereised MOTs into a
level shifter and an 833 tube with 8 uFd of filter caps
in the shifter and 5 nFd in the primary tank cap.

Thanks,
David

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