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Looking for transmitting pentodes.

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Arcstarter

Tue Oct 27 2009, 03:38AM

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

The more powerful the better. I wanted to get a GU-81M from eBay, but the shipping is a killer, so i will have to settle for a smaller tube from 4hv. Oh well :).

Of course, it is another thread to trade electronics for electronics. I have a few brick IGBTs i could trade (preferred), most pretty slow, bunch of computer PSUs that i do not care too much for, and if i must, i can trade an 811A. Modified induction motors that sync, and other junk. I can trade MOTs, i have 3 identical 1500 watt 8 pound MOTs, but nobody ever needs MOTs. Not to mention, 24 pounds for 3 of them. I can trade a tiny inverter welder transformer, but i would really rather not. It is 140 amps at something like 20-30% duty cycle and 100 amps at i think 80 or 100 welding duty cycle, at some 30v output. Have a few 1.6kw ferrite E cores, and maybe a bit of litz wire. I also have a solder on insulator in great condition, about 10 inches long. And, i always have that 50Kw 7.6kv pole transformer, provided you arrange pickup

Tubes i am looking for.

GU-81M
GU-50 (these are small and cheap)
803
813
GK71 (also fairly small and inexpensive)
Anything that is around 1kv plate voltage and up, and above 100ma i am interested in, but for small tubes like that i would not pay (trade...) much for.

I may be interested in tetrodes, too, but mainly just pentodes.

Thanks...

Proud Mary

Tue Oct 27 2009, 04:43AM

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

Hi Arcs, I'm not in a position to help you, because of the absurd postage charges, but have you thought of looking at sweep tubes, which have long been popular in the US for high power HF linear amplifiers?

Arcstarter

Tue Oct 27 2009, 05:09AM

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

Harry wrote ...

Hi Arcs, I'm not in a position to help you, because of the absurd postage charges, but have you thought of looking at sweep tubes, which have long been popular in the US for high power HF linear amplifiers?

Hi Harry.

Yes, i have thought about them, and i have used them. I love using the somewhat little tubes, they are fun! But, i am planning on just messing around with things like Tesla coils, and other stuff like that. It will be hard on the tubes, im sure, more than other applications. That is why i want a bigger tube. One of the tubes i listed was no bigger, in fact. The GM-50 is quite small, around 1kv plate voltage and 100ma or something like that.

I do not want to push them over the edge, though. If they get red, i turn it off and make it stop doing that

Proud Mary

Tue Oct 27 2009, 05:55AM

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

I get loads of very high quality stuff - unobtainable elsewhere - from the former "Iron Curtain" countries of the old Soviet Empire, some of which are now in the European Union - and are so subject to modest standard postage rates to England.

If you have the cash to pay for your power pentodes, I would look there on ebay - Lithuania, Latvia, Georgia, and so on.

Arcstarter

Tue Oct 27 2009, 07:59PM

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

I looked on eBay, but unfortunately all that helped was make me want a tube worse :P. No cash, that was the point of this thread.

ah well.

Dave Marshall

Sat Oct 31 2009, 04:31PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

Arcstarter, I'd recommend taking a peak at the GI-7B. They're fairly common on ebay for $18-$30, can dissipate at least 200w, and have a stupidly wide frequency range. They top out around 1GHz or so.

-Dave

Arcstarter

Sat Oct 31 2009, 04:38PM

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

Wow, 1GHz :P.

Unfortunately, the whole point of this thread is that i do not have a cent under my name

Not to mention, that tube is a triode

Proud Mary

Sat Oct 31 2009, 06:06PM

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

Arcs, I may be able to fish out a pair of decent RF output valves for you - frankly, son, unless you were born in the Thermionic Age you'll find life easier with a beam power output tetrode than a pentode.

Send us a sketch/outline of what you hope to achieve, and I'll see what I have that matches up to your spec.

I want no money for myself, Arcs, but you would be obligated to pay the postage from the United Kingdom, via Dave Marshall,
the Treasurer of the 4HV Grand Christmas Appeal.

I do have some VHF kW triodes like ACT28, which had a brief career as radar jammers, but I'd want to see a credible circuit diagram/US: schematic) for the PSU before I let one go at budget prices. (The ACT28 handbook contains instructions for the supplementary generator, and so on)

Your pal,

Christopher

Dave Marshall

Sat Oct 31 2009, 07:47PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

Hmm. Let me poke around Arcstarter. Perhaps we can do a deal for one or two of those IGBTs. I had one floating around in my collection somewhere, but I might have given it away.

-Dave

Arcstarter

Sat Oct 31 2009, 11:28PM

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

Harry:

That is very nice of you to offer, but honestly, i do not want a really nice tube. I am just messing with these tubes, maybe some random circuits, and i mainly want to experiment with high frequency plasma tweeter type circuits. This is probably hard on tubes, and rather pointless to get a very nice rare tube, just to run it hard. Though GU-81m's are large, they are apparently not too rare, so i would not but so scared to run it a bit hard.

Also, the GU-81m and other large tubes i listed would be run with less than what they are made for (voltage wise) because i may be pushing them hard (current wise).

Dave:

You mentioned on this thread, and in the IRC, that you may be interested in some of these brick IGBTs. I kept having to leave, something with my friend...

Just a bit of a warning, these are used. I will test before i send them out, though. Also, you said you may be using high-ish frequency, in the IRC. These may do 50KHz, some may not. I am sure most of them would...

Just let me know if you figure out what you are going to do, and what frequency you will be running. We can figure out if i have a brick that would suit your needs. Perhaps i have something else you may need, as well...

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