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VTTC theory & Staccato contollers

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U4R1A

Tue Dec 21 2010, 05:54PM

Registered Member #3505 Joined: Sun Dec 12 2010, 06:03AM
Location: Albuquerque NM
Posts: 108

So I'm still gathering all of my materials for my first VTTC and I was looking at the staccato controller and how it works. So I'm going to spit out what I think is happening and every one that actually knows can chime in to correct me. If I'm not mistaking the Staccato acts as a ground interrupt and regardless of the biasing of the grid no current will flow therefore zero sparks. So if your using a staccato to control the pulse rate what would prevent you from applying a positive charge to the grid continuously and completely leave out the feedback coil or better yet use a diode tube . The pro's to this would be one less coil to make and one less to get destroyed by flash over. Also you wouldn't have to worry about moving the feedback around for tuning. I'm sure there is a flaw in this reasoning some where but I'd like to hear what you guys have to say.

HV Enthusiast

Tue Dec 21 2010, 06:27PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

U4R1A wrote ...

So I'm still gathering all of my materials for my first VTTC and I was looking at the staccato controller and how it works. So I'm going to spit out what I think is happening and every one that actually knows can chime in to correct me. If I'm not mistaking the Staccato acts as a ground interrupt and regardless of the biasing of the grid no current will flow therefore zero sparks. So if your using a staccato to control the pulse rate what would prevent you from applying a positive charge to the grid continuously and completely leave out the feedback coil or better yet use a diode tube . The pro's to this would be one less coil to make and one less to get destroyed by flash over. Also you wouldn't have to worry about moving the feedback around for tuning. I'm sure there is a flaw in this reasoning some where but I'd like to hear what you guys have to say.

Yes, that is correct. It prevents plate current from flowing, thereby preventing the tube from switching.

Keep in mind, the Stacatta controller goes one step further. It turns the tube on at the beginning of the half-wave rectification cycle. So in otherwords, your tube begins operating when plate voltage is at a minimum (again assuming non-filtered or lightly filtered AC), and then as the tube is switching the plate voltage gradually increases which provides that nice increasing voltage envelope that creates the "sword-like" sparks. This is the same way that the so called QCW coils operate. They are pulsed in a similar fashion, and the DC bus voltage is allowed to ramp in a similar fashion per pulse, except with the QCW coil, you can create much longer sword-like sparks because you can increase the pulsewidth to times that are greater than your 60Hz AC input line period.

So for a Stacatto controller, its important to realize that you are both turning the tube switching on and off as well as synchronizing the switching with the AC line, to ensure you only turning the tube on during that rising plate voltage envelope.

Hope that makes sense.

U4R1A

Tue Dec 21 2010, 06:47PM

Registered Member #3505 Joined: Sun Dec 12 2010, 06:03AM
Location: Albuquerque NM
Posts: 108

So could you do away with the triode and use a Tube diode it its place since you're no longer really using the feedback of the coil to turn the triode off and on? To me it would seem the grid feedback portion would do nothing but clip the signal the staccato is putting out. It's like having two people switching a strobe a light but they don't talk to each other so the output would be messy and non orderly.

HV Enthusiast

Tue Dec 21 2010, 06:57PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

You *are* using the feedback of the coil to turn the triode ON and OFF. However, this carrier envelope is modulated further - being pulsed by the stacatto controller.

If your coil is resonant at 1MHz, for example, and your pulse width on the Stacatto controller is 5ms, then you will basically be switching the triode ON and OFF approx. 5000 times on each pulse of the Stacatto Controller.

U4R1A

Tue Dec 21 2010, 07:37PM

Registered Member #3505 Joined: Sun Dec 12 2010, 06:03AM
Location: Albuquerque NM
Posts: 108

I'm starting to smell what your stepping in. Does this increased modulation increases the output? I'm a mechanic by heart and i work on turbines and other interesting energy generating devices so i have to put the ol TC's into stuff i already understand. Normally when generating energy. Energy= N(speed/Hz)x(Flux density) So by using the staccato are we increasing the output frequency of the primary?

HV Enthusiast

Wed Dec 22 2010, 01:11AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

Read John Freau's article on development of the Stacatto mode of operation. Very good article!

U4R1A

Thu Dec 23 2010, 05:13PM

Registered Member #3505 Joined: Sun Dec 12 2010, 06:03AM
Location: Albuquerque NM
Posts: 108

That was some good info about the stacatto's origin. So lets say I'm in the building phase of my VTTC do I ground the secondary,filament,grid leak and mot to the mains ground and If so does any of that crazy RF get into your mains?

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