Hi Chris,
Do you see an improvement in spark length on your VTTC when using a larger toroid? I have 2 more turns of tuning available on my primary so I can try a larger toroid if that would help. Also, in lieu of rewinding my secondary, I have another small Murata Class 1 doorknob capacitor that I can put in parallel with my primary circuit capacitor to give me some more tuning range on the primary coil if needed.
Another possible improvement that I am considering is the addition of a heat shield between my primary circuit capacitor and the vacuum tube. My capacitor is a Murata Class 1 doorknob and it heats very little, just slightly warm to the touch. However, the capacitor is only about 2 inches away from the tube in the interest of keeping primary circuit connections as short as possible. The idea of the heat shield is to prevent the capacitor from being heated by radiation from the tube. That being said, I have run this VTTC for as long as 20 minutes in interrupter mode and have noticed no degradation in performance and very little capacitor heating so I am not sure that the heat shield will improve things. It is very easy to add, however, so I will probably do it.
Steve
----- Original Message -----
From: "Chris Reeland" <chrisreeland@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, March 16, 2018 3:30:07 PM
Subject: Re: [TCML] VTTC MOT question
Hi Steve,
Yes, I am back to my bigger copper tube toroid again. I have said in the
past recently that I always find myself going larger especially if pulsing.
I tried 4 other smaller sizes working back up to this. I have several more
going bigger, but of course they get too physically big for the size of
this coil, and then I would run into frequency problems again, which I want
to also say if you are considering larger, you may want to figure out if
you are going to have a possible frequency problem of pulling it too low.
This is why I rewound my secondary for a higher starting frequency. I have
alot more "headroom" to try various changes.
Yeah, having the feedback above a fairly tall primary can have some
problems. I have mentioned this also in the past. You got lucky you caught
is soon enough and have taken corrective action, I have seen variations of
what you said you did to prevent this.
Me, I have stopped a while ago of the "traditional" above the primary. I
always put it below now. Me, I feel (and some may disagree with me, which
is ok) that even though in theory, it is only supposed to be affected by
the primary, it seems to be affected by the higher voltage built up on the
secondary on the upper end, which happens when you have a taller primary.
If a short traditional primary, it is ok above.
At the bottom below the primary, you are of course located at the bottom of
the secondary, which is mostly current of course, and also has the benefit
of eliminating high voltage short arcs between the feedback and secondary.
I would also say this is much healthier for the grid wire of the tube to
eliminate this from happening.
I will have more details on this later, but I "was" peaking during the
pulses about 23+ amps at "140" 100% variac input.
I have not yet done any changes yet last night or today yet. Kind of taking
it easy...was tired from work. Going to mess around a bit later I think.
I should be able to give more details and comments and pictures this
weekend sometime.
Chris
Sent from my LG V20
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