Re: GMI-90 Project ideas
Arcstarter, Sat Apr 04 2009, 09:43PM

There is always the regular vttc, but you could perhaps put a small twist on it. Vacuum tube disruptive coil XD. 40 amps is really low for this though, soooo...

You could make a hf vttc, since it is a tetrode. You know, the 'plasma tweeter' circuit, secondary base fed and no primary.

A very ridiculous audio amp (yes this is a joke, unless you wanna be a bit different XD)

A low power induction heater.

A hf oscillator for assorted thing.

What would you use for power? A flyback is what i would use . Have fun, good luck!

Re: GMI-90 Project ideas
Dr. Drone, Sun Apr 05 2009, 08:19AM

Re: GMI-90 Project ideas
Littlew, Sun Apr 05 2009, 06:39PM

You can make pulsed vttc or earn some money(gmi-90 had 0.7g of gold and gmi-7 had 2g of gold and 0.1g of silver)

Re: GMI-90 Project ideas
Dr. H., Sun Apr 05 2009, 07:05PM

Good day guys

I will most likely go with the Bipolar VTTC but will be open for ideas because it won't be soon when I will start that project.

Hmm break the tube and get the gold to sell it ?!? - I can make much more by selling the whole tube. And how can you break such a beauty ?!? This thing is staying with me, if not used - will go to a good friend of mine

Cheers

Re: GMI-90 Project ideas
Steve Conner, Sun Apr 05 2009, 08:51PM

I'd go for a disruptive DRVTTC for sure. 30 amps might not seem like much, but remember it's 30 amps at 33kV: 1 megawatt of pulse power.

Even allowing for some derating, as a disruptive coil burst is typically 150us, not 3, I'd still expect sparks over 3ft from it. Maybe only 1 or 2 per second on account of the 140W continuous plate rating.

Re: GMI-90 Project ideas
Arcstarter, Sun Apr 05 2009, 09:10PM

See Mr. Conner has the right idea XD. Just use low tank capacitance. You could make a normal Dc resonant charging power supply, and use the tube as if it where a spark gap. I tend to think that might be easier on the tube, as it does not have to oscillate at such high freq, and you would use an anti-parallel diode to carry the oscillations on so that would only be half of the oscillations the tube has to conduct for. Then you can use a higher breakrate and stuff. It could use sidacs to trigger the tube at the right voltage. I was thinking something like the sidac's in series, when they break down they charge a small capacitor up, then some TVS's could let the cap only charge high enough. On the sidacs you would of course have a power resistor to keep tank cap from discharging through the sidacs. The capacitor could be adjusted to set on time, and it would have a bleeder across it.

You could also use a low freq oscillator and a half or full bridge, running a steup/isolation transformer tied to the grid. (gdt now equals GRID drive transformer :P)

Just ideas that for some reason i thought i should write down...

Re: GMI-90 Project ideas
Dr. H., Mon Apr 06 2009, 05:56AM

Good day guys

BIG thanks on the repplys

Now for the disruptive DRVTTC - I've been thinking on that for a long time and for it I have a much "better" tube than this one.
A russian triode at 10kV plate, 1A continuous (130A pulse) and 4kW dissipation power on the plate.
Hmm 2-3 burst in a secound sounds a "little too little". Any suggestions welcome

Cheers !

Re: GMI-90 Project ideas
vasil, Mon Apr 06 2009, 03:38PM

Nice looking tube. I have one also in my collection for a future project:



...but this will be only after I would finish the GU5B project. Unfortunately, I had not enough time lately. I just managed to build the primary cap and the cooling pipe (for GU5B) only:





I still dont know how to put the tube (GU5B): anode up or down. The device is made for the tube with the fillament connections up..

I thought to a bipolar VTTC too for the gmi90, center grounded, g2 modulated (as a drsstc). When the project will be started I dont know....

Re: GMI-90 Project ideas
Erlend^SE, Mon Apr 06 2009, 10:21PM

Given the voltage, maybe Audio Amp for electrostatic speakers?

I know they use a rather high voltage, maybe 30 KV would do?

(I don't except it to be used for that, anyway... but just an idea)

Re: GMI-90 Project ideas
Littlew, Fri Apr 10 2009, 03:13PM

put gu-5b's anode down(this information was taken from tube's datasheet)

Re: GMI-90 Project ideas
Mathias, Sun Apr 12 2009, 09:59AM

Well i also found one lying around. So i'll do someting with it in the near future. A bipolar DRVTTC would be neat

Re: GMI-90 Project ideas
Proud Mary, Sun Apr 12 2009, 11:15AM

I make things with valves all the time, and I would hesitate to take on a project requiring such a large and expensive power supply, though your own circumstances may be very different.

Big HT transformers have never been cheap, but now their prices have gone through the roof.

You can't make energy out of nothing, so unless you are confidant that you can afford not just a heavy-weight PSU, but all the supporting circuit architecture and metalwork that such a valve requires to function properly, you'd have less heartbreak trying something else.

Imagine such a valve in its original context, and I see in my mind's eye the kind of equipment housing that has double steel doors on the front, with fat cables to supply it with power and instructions.

At the risk of sounding negative, with valves of this size I'd suggest that if you have to ask it means you're not really ready to think seriously about using them. That is why very large valves may be bought so cheaply.

But Good Luck with it all! At worst you have a splendid paperweight!

Re: GMI-90 Project ideas
kilovolt, Sun Apr 12 2009, 12:07PM

I'm not sure but I think at 30kV anode voltage this tube might produce significant x-rays ...

Greets kilovolt

Re: GMI-90 Project ideas
Mathias, Sun Apr 12 2009, 12:07PM

Thanks for caring and giving advise. Also, Yes i'm fully aware of what will be required for a project of this caliber and the tasks ahead.

Basicaly what i'm thinking, is to build some "huge" tesla system(s) for the "Palace of Wonders" that will open sometime next year. So relative cost and a place to power and operate such device(s) wont be a problem. So for now sky is the limit. But then again maybe you'r right and it won't make up for the time and effort invested in it. Right now it seems to be a good idea that's in planning phase.

Re: GMI-90 Project ideas
Proud Mary, Sun Apr 12 2009, 01:09PM

As a Living Fossil of the Thermionic Age, I'd guess that circuits using this valve would have been put together by a design team of six or twelve men working on it for half a year before a prototype was constructed and costed out.

It's true that today you can simulate circuit operations with PSpice and the like, and save countless hours with a slide-rule where the value of every component had to be individually calculated, but you won't achieve stable and reliable operation with a device of this kind without great attention to engineering detail, and several prototype iterations before the design is declared to be trustworthy and fit for purpose.

It's a bit like asking how you could you fit a 1950s jet fighter engine to your car by next summer....

I think that using valves is a great idea - I always encourage anyone on the forum who wants to keep the old technology alive, since it still has much to offer for special applications - but if you aren't well schooled in valve circuit design, I'd look for an easier route into thermionic technology than a valve of this type.

Others will surely disagree, but there's my six-penny-worth, and I wish you well.

PS. X-ray screening should always be used with valves operating above 20kV.