Re: [TCML] Tube choice for a VTTC

[nancylavoie@xxxxxxxxxxx]

Any chance a pair of GL~860 tubes could be made to work? I have them and would love to put them to use. Not sure on the specs though.
Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: futuret@xxxxxxx

Date: Sun, 14 Jun 2009 13:30:11 
To: <tesla@xxxxxxxxxx>
Subject: Re: [TCML] Tube choice for a VTTC


Dave,

I think as a practical matter, just about any kind of power tube can
work well
in a VTTC provided it's robust and can withstand the voltage, etc.  I've
used tubes such as; 833A, 833C, 803, 805, 810, 845, 304TL, 4-250A,
4-125A, HF300, HF200, etc.  All of them worked well.  Some coil designs
seem to require a lot more tweaking to make them perform well.  Some
designs tend to produce fuzzy sparks, whereas others produce spikey
sword-like sparks.  It's not completely known why this occurs.  There
is some evidence that a higher frequency helps to produce swordlike
sparks, but I know that other factors such as tube type, tuning,
coupling,
and feedback all affect this also.

I think the addition of a small toroid to a VTTC may help to stabilize
the operation.  A toroid seems to help the spark output some also.

Perhaps at some point, someone will try to quantify all this, and maybe
make up some sort of computer design program to assist with VTTC
design.  Some of the known rules of thumb, formulas, and general
principles could be incorporated into the program.  I think there's
still
a lot of unknowns about tube coil design and operation.

Cheers,
John


-----Original Message-----
From: David Speck <dave@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sun, Jun 14, 2009 8:52 am
Subject: [TCML] Tube choice for a VTTC


List, 
 
I've read previously that the best=2
0tubes for VTTCs are ones with low
Mu's or amplification factors.  
If one were to happen upon a high Mu tube at a good price, is there a
way to adapt the VTTC grid or primary circuits to make it work well?  
Would using fewer turns in the grid coil or some sort of resistive
voltage divider be sufficient to optimize performance? 
 
Does the high Mu make it harder for the system to remain stable when
the coil is loaded by the streamers?  
Can anyone recommend a good reference book on the design of high power
vacuum tube amplifier/oscillator circuits? Seems all I can find are
books on guitar amplifier construction, a little small for my tastes.  
Thanks, 
 
Dave 
 
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