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GU5B VTTC project

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LAN_403

Wavetuner

Tue Jul 28 2009, 07:49AM

Registered Member #1500 Joined: Sat May 24 2008, 04:38PM
Location: Ojai, Ca.
Posts: 44

Wow, Nice tube coil!! I'll have to look up that tube's specs. My question, which is what I am strugling with, is creating a stiff power supply. What are you using?I am to the point of rewinding with added turns on he two outer coils and rewind the center core as the primary on a former 3p transformer. Usually this scenario the outer coil are wound in reverse. Will I need to cut one off and rewind one or can I wire the secondaries in reverse series. Does anyone know if this will work? Also all cores are the same size which is wierd Do I need to machine the outer cores thinner? The core is reversed E core, oh goody.

There was areally nice plate transformer on ebay awhile ago but I was too tight on cash at the time. I am not sold on MOV's though I have 4 identical 1100watt ones but am not happy with them. They just weren't designed for CW operation. We tend to forget that when we use doublers for voltage we half the current

I want a 4500v or so transformer, even if I have to wind it. I would like to run it raw or CW with stacatto. I have a great core for the project. Does anyone know if the HV windings have to be wound in oposite or can they be reverse series connected?

Again, a really nice coil! Very motivating:-D

Jim Mora

Wavetuner

Tue Jul 28 2009, 08:13AM

Registered Member #1500 Joined: Sat May 24 2008, 04:38PM
Location: Ojai, Ca.
Posts: 44

wow, that tube rocks! 5kv, 3.5kw!! I wonder what it will do with a stacato reduced duty cycle!

vasil

Tue Jul 28 2009, 01:26PM

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

I am using a strange configurations of 4 MOTs, with different outputs, in a level shifter, here is its construction thread:

http://4hv.org/e107_plugins/forum/forum_viewtopic.php?60496

I had to use what I have in my hands. Probably, not the best solution, but this is it. Now, I will re-wire it to get twice output voltage, at the same power level (I hope).

I will build a staccato before trying higher voltages. It would pity to distroy such nice tube.

Wind your secondaries in reverse and attach the inner output to the core (ground the core). That would reduce the electric stress.

vasil

Sun Aug 02 2009, 05:58PM

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

Got the A-meter (0-600 mA, I hope that is enough). Working on staccato.

vasil

Sat Aug 22 2009, 08:09PM

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

Well, some good news.

Added a staccato, that's the low voltage side:

I made myself a lighter heatsink from an aluminium sheet:

I am very clumsy when soldering (had burned a lot of transistors along the time), so I put them in chip sockets:

Added 2 new MOTs to my power source (that's 6 MOTs in serie-parallel).

Results:

MOVIE 1

Retuning for a lower frequency on primary tank gives up to 80 cm:

MOVIE 2

I think I reached my power limit. Even at this low rate, the power cord is hot after 1 min of run and I have epuised my MOT stock. But I think that Dr H has right, the tube can take more abuse.

Enjoy

Dr. H.

Sat Aug 22 2009, 10:06PM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Good day Vasil

I am glad you are still working on the coil. The results are looking great

... and I still think you will be able to squize a bit more out of it. Without a staccato I was drawing around 28-30Amps (atleast that is what the analog A meter showed) at 240V to produce 100+ sm of sparks. Have in mind that I was using only TWO MOTs ... this makes me think that you have to tinker with the tunning/tickler coil, try different secondaries and toploads. Also play with the grid feedback circuit. I've noticed a dramatic increase/decrease in spark lenght only by moving the tickler coil a couple of sm up or down. Another important factor - the level shifter capacitor - placing to big of a cap on mine decreased the spark lenght dramatically. I've had a 3.5uF (or something like that) in the beginning and I've ended with using only 1uF for best results. Sooo keeep experimenting.

Cheers

vasil

Sun Aug 23 2009, 05:34AM

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

OK, I will do it

I liked the idea to have the feedback tapable, thats why I made it with heavy wire and taps. I will make a new one with magnet wire (20-21 turns) and place it above the primary. Still afraid to think what can happen in a breakdown.

The doubler cap is now 2.6 microF. Not too much..but I can experiment with different values.

Do you think that a different secondary would work? Making secondaries for 300 kHz, 400 kHz (increments of 100 kHz) would be a good idea? I am too lazy to winding though.

I will rebuild the source. Indeed with more MOTs the sparks is hoter not longer.

I tryed a bigger toroid but didnt notice semnificative better results (only more fiercely and hoter sparks).

In the precedent VTTC I got a few cm of sparks just lowering the primary cap at only 700 pF from 1.1 nF.

I will experiment a bit.

Dr. H.

Sun Aug 23 2009, 06:22AM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Good day Vasil

I am not shure what frequency the tube "preffer" to be at - I've got the best results at around 360khz. From experiments - tubes seem to like the 300-400khz range. Also noticed that my coil didn't like big torroids - it ran much happyer with smaller ones. I've had tube arcing and other problems with big torroids.

My secondary is about 70sm tall wound with some very thick wire. (don't ask about size don't remember

)

I think you shoud up the Cprimary and lower the turns. I would go with 1.1nF or even a bit bigger and tune it with the primary (watch the tube ! ) Decreasing the cap value and with soo much and getting bigger sparks suggests you are out of tune ! A lot.

On the feedback coil - make it "movable" tunning this coil is critical ! But take your time making it properly because it will be a great "ground" target for the sparks (this is where I have problems). In my experiments changing the number of turns didn't changed a lot but playing with the feedback circuit *(the C and the R ) made a GREAT difference.

Cheers

teravolt

Sun Aug 23 2009, 06:43AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

DR. Spark got better results in the end by using about 10 turns of 2 awg wire on the primary. Lower inductance higher capacitance makes for larger circulating current. Remeber that 3.5kw is the power disapation of the tube in heat. If the tesla is 75% ephishant as in class C then the other 25% is heat mainly in the tube. With about 5 mots you should put out as much as Quadzila. Please feel free to correct me if I am wrong

Wavetuner

Sun Aug 23 2009, 09:21AM

Registered Member #1500 Joined: Sat May 24 2008, 04:38PM
Location: Ojai, Ca.
Posts: 44

Wow is #2awg a typo? I plan to use .1865" soft copper tubing seperated by equal size heavy fishing line. Maybe I should scale that up? This is also a quad 833C.

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