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Suitible tubes for a VTTC?

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aonomus

Mon Jan 05 2009, 05:37AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Dr. Spark, what *don't* you have :P

From the looks of it I might be really hard pressed to find transmitter tubes, but I'll keep my eyes peeled, with any luck I will find them, if not, oh well.

Dr. Drone

Mon Jan 05 2009, 06:06AM

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

Proud Mary

Mon Jan 05 2009, 08:39AM

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

Television line output valves (US: "sweep tubes") can sometimes be found in job lots of junked valves, though their prices are rising.

They were designed to be perhaps as near to a switch as thermionic devices had ever been, and can handle very high pulse currents for their size.

Here are some types you could keep an eye out for, though there are surely more:

PL504, PL509, PL519, 6GJ5, 6HF5, 6JB6, 6JE6, 6JM6, 6JG6, 6CD6, 6DQ6, EL509, 6LX6, 24JE6A, 6JB6A, 30KD6, 40KG6, 36MC6, 26HU5.

These are not great monsters like 813, but can output between 30 and 45W if you follow the manufacturer's ratings, and probably more if you overdrive them in the usual 4HV way!

All but a few of the "Compactron" series have anode top caps.

Medium power transmitting valves like 807 are also worth a look, and can often be found inexpensively.

If an unknown valve looks interesting, hold it up to the light and see if you can count the number of grids between the anode and the cathode.
If there are none, then it is a diode or rectifier or gas valve of some kind. If there is one, a triode, two a tetrode ("screen-grid tube") three a pentode, four a hexode, five a heptode (US "pentagrid") Follow the metal connecting ribbons with your eye and see how many of them go down into the base. How heavy does the anode (US: plate) construction seem to be? Much can be learned by using your eyes.

The valves you are looking for are likely to be triodes, tetrodes, and pentodes, with tetrodes being by far the most common in the power classes.

Valves can usually be driven in parallel without much complication, so two easy-to-get, inexpensive ones can often be used rather than one single big costly affair.

Good luck with your search!

Zenador

Mon Jan 05 2009, 02:14PM

Registered Member #1733 Joined: Thu Oct 02 2008, 03:17PM
Location: Hamilton, ON, Canada
Posts: 100

aonomus, When are you going to "the store"? I was planning on going there around 12:30, be nice to meet up...

He has more tubes than the ones in the boxes on the floor. He keeps the more "valuable" stuff behind the counter. If he has triodes, that's where they would be.

Littlew

Mon Jan 05 2009, 04:52PM

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

Good tubes(they are russians, but i think there is some analogs of tubes) for VTTC:
GU-81
GK-71
GU-80
GM-70
6P45S(low power)
GD-400

LithiumLord

Mon Jan 05 2009, 06:02PM

Registered Member #1739 Joined: Fri Oct 03 2008, 10:05AM
Location: Moscow, Russia
Posts: 261

hehe bet it's really both a good idea to look for and a good chance to find old Soviet tubes in Canada lol. (especially the search for 45s is worth the time as I only saw a single good-working project on it)

In fact, any low-impedance generator tube will work, just make sure the grid capacity is low enough.

Proud Mary

Mon Jan 05 2009, 09:34PM

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

One can get truly excellent bargains with big transmitting valves from Russia, such as the famous GS35B which has an anode dissipation of 2kW (3kV @ 1.4A) with forced water cooling. But beware if you are not experienced with valves of this type! They are not 'run in' when you get them new, so you should run the heater continuously for 48 hours, with forced air cooling to properly anneal the copper seals. They then should be run in at much reduced power with minimal grid bias for another day before the full anode voltage is applied, or they are likely to flash over and self-destruct.

aonomus

Tue Jan 06 2009, 12:05AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Sadly the store had none of the tubes, however there is hope yet with a hamfest or two around the corner in Feb.

When I get the chance today, I will see about putting most of the tubes onto the VTTC wiki page.

Dr. Drone

Tue Jan 06 2009, 12:53AM

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

aonomus

Tue Jan 06 2009, 01:57AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Zenador wrote ...

aonomus, When are you going to "the store"? I was planning on going there around 12:30, be nice to meet up...

He has more tubes than the ones in the boxes on the floor. He keeps the more "valuable" stuff behind the counter. If he has triodes, that's where they would be.

Sorry, I had classes at that time, didn't even notice this post. I ended up spending an hour downtown picking stuff up, and now my feet have massive corns.

Edit: I just threw up the bulk of that list onto the VTTC page on the wiki, but that page is very sparse on information and needs an overhaul, if people are willing to contribute they should. Also the table of tubes should probably be forked onto its own page so that extra notes, links, important values, etc can be listed.

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