GU5B VTTC project / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

GU5B VTTC project

1 2 3 4 next

Move Thread

LAN_403

vasil

Sat Jun 27 2009, 06:18AM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

I started this project a few mounths ago, sorry for the slowly progress as the time was...and will be a big problem. Finally it will arrive to an end.
I built the main components, there are a lot of little things to do yet.

The secondary: 11 cm PVC pipe, around 1200 turns with 0.4 mm magnet wire. It was varnished (looks like crap, because I have not enough varnish) but I hope that the turns will be held in place (this secondary will heat a lot). I will use a little toroid too.

The primary coil has around 60 turns with taps from 20 turn (I will remove maibe some turns after tuning) with 2.5 mm insulated solid copper wire pn a 20 cm diameter PVC form. The tickler has 30 turns with taps from 5 turns.

The primary cap is a serie-parallel combination of big ceramic russian caps, 2200 pf @ 6 kV, 35 kVar each, for a total of 1.46 nF @ 18 kV

The first cooling socket for the tube used an externally source of fresh air:

But Limke told me that a simple fan cooler will be enough for short runs, so I re-made it in a more elegant solution:

There will be 1-2 more fans on the sides of the tube.

The power source will be my last 4 MOT doubler (or just another strange combination of different MOTs):

I am worry a bit about my variac (is 2 kW only).

I have to work in an appartament room, the neighbours don't like the noise. So, I am using only manual tools.

It will take more time, but hope to finish it soon. I have to make the base and heat the fillament for sealing the tube.

Dr. Drone

Sat Jun 27 2009, 11:00PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

Proud Mary

Sun Jun 28 2009, 12:32AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

12.6V @ 25A for each filament!

Given the relatively short run times, you might consider using float-charged lead-acid batteries for the filaments to save time, trouble and money.

The averaged filament characteristic curve in the data sheet suggests that this valve was intended to have a mobile or remote operation capability by means of auxiliary 12V lead-acid batteries, as the curve tracks the whole range from 12.6V at full charge down to 3V full discharge - 0,5V per cell.

vasil

Sun Jun 28 2009, 05:34AM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Secondary characteristics:

-11 cm diameter grey PVC pipe
-total lenght: 50 cm
-wound lenght: 48 cm
-magnet wire 0.4 mm
-1200 turns
-2 varnish layers
L = 32247.595 microH
C self = 7.7806 pF
F0 = 317.896 kHz

with a 11.77 pF toroid, the frequency drops to 200.544 kHz.

So it would make probably branched sparks according to the frequency theory (though, I think it depends also by the output electrode shape and position, I will see).

The fillament transformer was made on command here:

http://www.petra-toroid.ro/cere-oferta.html

No load voltage = 13.4 V (it will drop under load at 12.6 V)
Max curent = 25 A
Rated power = 350 W
Toroidal transformer type
Breakdown interwinding voltage tested at 4 kV
It will has some big power resistors on the primary side for pre-heating fillament.

I have to set the tube in position and put the fillament to work. I will slowly crank the voltage on the fillament transformer with a variac to see what is the output voltage under load (maibe I will need a few more turns). Pics soon.

Proud Mary

Sun Jun 28 2009, 06:04AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

vasil wrote ...

with a 11.77 pF toroid, the frequency drops to 200.544 kHz.

That's a very convenient frequency, Vasil.

vasil

Mon Jun 29 2009, 06:16PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Yesterday I was very busy....hmm...hmm

But today I've found a hour for the coil. I put the cooler on the base. The screws from the cooler will allow air input to the fan and will decrease the socket vibrations.

Preparing the tube:

Finally at its place:

The grid and fillament connections:

vasil

Sat Jul 11 2009, 10:28AM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Made a few things today:

-put the fillament transformer in place

-made the fillament connections

-had to wait a long time to get a big resistor for pre-heating circuit (that's 56 ohms at 160 W). It is set up in the primary circuit of the fillament transformer.

-started formating the tube. I would have 12.4 V at 230 V, but in the middle of the day the mains voltage drop to 213 V. I will not modify the fillament transformer (adding extra turns), because if the mains voltage turns to normally I will overvolt the fillament.
The sound is from the cooler placed under the tube. The anode heatsink is warm after 30 minutes of run.

FORMATING THE TUBE

Hopping to put it together in a few days.

vasil

Wed Jul 15 2009, 04:58PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Put all the things together. It is huge, but I need some space for cooling down some components and the wood plates I am using are so small....and I dont know where to put it in my room....

Have to add some more coolers and make the electrical wiring.

vasil

Tue Jul 21 2009, 06:32PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Almost ready. Pre-heating, wiring, coolers. Not sparks yet, sorry.

http://www.youtube.com/watch?v=syRoYHKmwfo&feature=channel_page

A few tips about preparing the tube:
How much time do I need to heat the fillament to seal the tube, before applying HV? A few hours? 24 h? A few days?
And how much time is necessary to run at low power level?

The little cracks you are hearing are not from my old bones..hehe... they are from the wooden floor.

StevenCaton

Wed Jul 22 2009, 12:25AM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

Looks good Vasil.

I can't tell you how long you need to burn in that specific tube, but a tube such as the 833C for example, should have at least 10 hours bake time. When I built my 833C powered VTTC, I was gone one whole weekend so I just let the filament cook the whole time.

You are aware of the fact that a low Fo secondary resonator tends to cause the sparks to "branch out" right? Your spark length may suffer a little bit from a low Fo setup. Chris Hooper had this problem on Quadzilla. But hey, you already made a secondary so give it a try for sure.

Also, are you going to be building a pulser circuit with a triac, scr, etc?

1 2 3 4 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob