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LAN_403

Dr. H.

Sat Apr 04 2009, 08:17PM

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

Good day guys

I've got one of those tubes (GMI-90) and I was wondering what project to do with it.

It is a tetrode with some interesting specs

33kV (yes 33kV) anode voltage

anode current - pulsed - 40Amps (3uS duratation)
Power on the plate - 140W (yes a little low)

Here some info on the tube

And some pics afcourse

(it is the one on the left - the others are for reference)

All ideas are welcome :)
Cheers

Arcstarter

Sat Apr 04 2009, 09:43PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

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!

Dr. Drone

Sun Apr 05 2009, 08:19AM

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

Littlew

Sun Apr 05 2009, 06:39PM

Registered Member #1448 Joined: Sat Apr 19 2008, 01:16PM
Location: Russia/Moscow
Posts: 21

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)

Dr. H.

Sun Apr 05 2009, 07:05PM

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

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

Steve Conner

Sun Apr 05 2009, 08:51PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

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.

Arcstarter

Sun Apr 05 2009, 09:10PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

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...

Dr. H.

Mon Apr 06 2009, 05:56AM

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

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 !

vasil

Mon Apr 06 2009, 03:38PM

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

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....

Erlend^SE

Mon Apr 06 2009, 10:21PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

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)

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