Dave, The primary frequency might need to be considerably lower than
the secondary, even considering the spark capacitance. This is because
of the double-hump tuning of overcoupled tuned circuits. The grid coil
couples mostly with the primary. If you have the same number of turns
on primary and secondary as Steve's coil, then that should put you
into the ballpark for tuning. Of course if the wire thickness or spacing
is different that will affect things. What you could try is put Steve's
specs into JavaTC to see what frequency his pri. and sec. are running at,
then make your coils have that same frequency ratio. Staccato won't
have much effect on the spark length. Since your coil works better
when you raise the grid coil, this could mean that you have too many
turns on the grid coil and are over-driving the grid. This can reduce
the spark length. But usually raising the grid coil compensates for
this pretty well as you have done. Someone suggested that your
caps might be defective. That might be something to check. In any
case the tube and variac seem to be good. So the problem must
be something else. If the coupling on your coil is different that
Steve's, that will affect the needed tune point too because of the
splitting of frequencies that occurs with double tuned circuits.
Can you post photos of your coil somewhere? That might give
some clue about things. Usually the tuning is not that critical
on these coils anyway (except if you want max. efficiency).
I'd say it must be a tuning issue, or maybe a bad capacitor or
some other component. You might want to verify that the grid
leak resistor and capacitor are good also. If those are bad it
could very much affect the operation. The resistor could be
open, or the capacitor bad. I think I got about a 19" spark
when I built an 810 coil one time, that was without staccato.
John
-----Original Message-----
From: David <zipo@xxxxxxxxxxx>
To: tesla <tesla@xxxxxxxxxx>
Sent: Thu, Dec 14, 2017 10:59 pm
Subject: Re: [TCML] 810 tube coil
John thanks - 16" sparks from an 810, wow I would be happy with 11. I am using a level shiftier w/ 2uF and the plate can get very red if I push it. I have a milliamp meter on the ground side and it easy gets to 300ma or more using a 140v variac. The tube can get very red if I push it to 250 to 300ma or more and that's at ~50% on the variac. I've ajusted primary turns from 36 to 44 with very little change. I've adjusted the height of the grid coil with little change tho it seem to work better the higher it is. Does the grid coil couple with the primary coil or the secondary? Steve was using a Staccato controller and I'm not yet. I'm using component values and set up as outline on Steve's page. For spark capacitance on Java TC I add a small diameter cylindrical topload by the length of spark in addition to the toroid and it seems to be pretty close. For tube coils is the tank suppose to match the secondary res frequency with spark and topload?DaveOn 12/14/2017 8:22 PM, Futuret via Tesla wrote:> Dave,>>> If you're using the voltage doubler (level shifter), then you should> get 16" sparks like Steve got. Does the plate of the tube get dull> red if it runs awhile? This might be seen more easily in a dark room.> If the plate gets red then it means the tube at least is capable of> strong emission. Even without the doubler it should produce 11"> sparks. However the coil will need to be tuned differently for> high power vs. low power operation to adjust for the> capacitance provided by the spark length. Is the 810 tube known> to be strong and good? A weak tube will give weak sparks, and> the plate will never get red (or probably won't). If you used JavaTC> or some other program to tune the coil, you may need to use a 50%> larger capacitor than the program suggests to adjust for the> capacitance of the spark. I think JavaTC might have a feature> that takes spark capacitance into effect (I forget). If it does then> that can be used. But it still might need to be tuned a little> differently. Also Steve might be using a step up type variac> which can provide up to 140 VAC to the coil. That makes a> large difference in spark length compared to using just 120 VAC.> An easy way to check the tuning is to install different sized> toroids (or no toroid), and see if the sparks get weaker or> stronger. Here's my website where I show a smaller VTTC project.>>> https://sites.google.com/site/jfuturet/home>>> John>>>> -----Original Message-----> From: David <zipo@xxxxxxxxxxx>> To: tesla <tesla@xxxxxxxxxx>> Sent: Thu, Dec 14, 2017 3:54 pm> Subject: [TCML] 810 tube coil>> Hello everyone - I have completed my first tube coil using a 810 triode> based on Steve ward's 810 coil outlined here,> http://www.stevehv.4hv.org/VTTC4.htm> I've almost exactly copied his design but with mica transmitting caps.> I've been working with trying to tune primary turns and adjusting grid> coil height and turns and have been getting ~4" sparks from the breakout> point, I would have expected more.> I'm not using a staccato yet but how much should I expect from a coil> like this at 60Hz?>> Thanks> Dave> _______________________________________________> Tesla mailing list> Tesla@xxxxxxxxxxxxxxxxxx> https://www.pupman.com/mailman/listinfo/tesla>> _______________________________________________> Tesla mailing list> Tesla@xxxxxxxxxxxxxxxxxx> https://www.pupman.com/mailman/listinfo/tesla_______________________________________________Tesla mailing listTesla@tedward.pupman.comhttps://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxxxxxx
https://www.pupman.com/mailman/listinfo/tesla