Re: All who know VTTC stuff ;-).

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: FutureT-at-aol-dot-com 

In a message dated 7/14/04 7:39:40 PM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

>Original poster: Kreso Bukvic <kreso.bukvic-at-kc.htnet.hr>
>
>Hy i would have 7 questions.
>
>1. How to determine is the VTTC in perfect tune or is it not?


Kreso,

You can build a variable capacitor or change the capacitance
by adding or subtracting small capacitors to change the capacitance
in small steps to see if the spark length improves at any point.

You can also change the primary tap point.  However you
must be aware that this changes the tank impedance and
may cause changes unrelated to tuning.  Small tap changes
will reflect tuning changes more than impedance changes
especially if the tuning is close to begin with.

Another way to check tuning is to vary the size of the toroid.
If the sparks get longer with a smaller or larger toroid, then
the tuning was probably not quite right originally.

Interestingly, the tuning if it is close will not affect the spark
length, however the tube will run redder for that spark length.
In other words better tuning may not lengthen the spark, but
will make the tube run cooler and reduce the power draw.
I'm assuming you want to tune for longest sparks with minimal
input power.

Adjustments of grid feedback, grid resistance, tuning, coupling,
etc, tend to interact.  Much adjustment may be needed before
optimal results are achieved.  My best VTTC's achieve an
"efficiency" of:   (without staccato)

   spark length inches = 0.5*sqrt input watts.

>2. If the secondary is wound slopili and has many knick does this influence
>the spark length?


Probably not much influence.

>3. If i will rewind the secondary with same number of turns but without
>knicks and overlaps, will i have ot retune it?


Probably the tuning will be very similar.

>4. I just noticed the tube has a small airbuble in glass ( i could post a
>picture). It works perfectly, but should i be worried?


Probably this is not a problem.

>5. If the filament transformer is rated fro much higher current than the
>tube needs can it do any harm ( my tube needs 5 V 14.1 A i have 5 V 30 A).


Current rating doesn't matter as long as it's enough.  What matters is
the voltage.  The tube will only draw the rated current if
the voltage is correct.

>6. Will stacatto improve sparklength? On my SSTC it improwes it by ~200 %.


It depends.  Sometimes it won't help, other times it will.  By using
staccato, you can increase the peak power but keep the average
power low for longer sparks.

>7. Will an improper diode decrease performance? I curently have 6 diode
>bridges in series ( greatzes).


I guess this if for a voltage doubler or level shifter?  Probably not
a lot of effect on performance will be seen.  Operation on filtered
DC without staccato will cause the sparks to be short, but draw
terrific power.  Raw AC operation with staccato tends to be
efficient.  Staccato can be used with filtered DC but is tricky
to implement.  Staccato is easily implemented using a mechanical
rotary switch from the filament to ground.  If the tube is a tetrode,
an AC 50Hz sample of the power line can be fed to the screen
grid to simulate AC operation and make electrical staccato operation
easier.

Do you ever get the very straight swordlike sparks such as can
be seen at my website?  (in the staccato mode)

   <http://hometown.aol-dot-com/futuret/page3.html>http://hometown.aol-dot-com/futuret/page3.html, 


click on tube coils (I think).

John


>Thanks for answers
>
>Best Regards
>
>Krešo Bukvi
>