The AM Forum

Isn't this a cool tube or what?
Trade in your ol' 813's.
Should be good for easy 200 watts dissapation in AM service.

http://qro-parts.com/product_info.php?products_id=82 (http://qro-parts.com/product_info.php?products_id=82)

Wonder how long they'll be available.  The claimed service life is phenominal.

Heh, I like how it has a clamp around it so that it can't leap out of its socket.

Rob W1AEX

yeah, when your flyin' a Mig 29 you need all the 'g' proofing you can get ;D

Looks like a Russian version of the old Western Electric 701-A tetrode.  It was sort of a 304TL with a screen grid.

I wonder if that company will still be around in 25 years to make good their guarantee.

It might be a good tube.

When I first saw it I thought it was a compactron! - until I saw the scale.  Jeeze, it's a fat bottle, over 3" dia. and over 5" long.  At $110 each I'm tempted to buy a couple.  - Maybe a pair modulated by a pair and would you get a load of those internal plate 'fins?'  From the broken Eng. literature I guess those internal fins are supposed to 'channel' electrons.  Sort of like Eimac 8877's focused beams where the grid is aligned precisely but at the plate?

Also their 40uf/5kv cap. looks very stout.

I'd say the external fins on the plate are for heat dissipation purposes.  Like the heat radiating fins on the older versions of Eimac triodes (304TL, 100TH, 250TH, 450TL, etc.)

oh yeah, definitely what the external fins are, but look inside the plate in the one three-quarter view if you haven't already.  You can see myriads of smaller fins pointing radially inwards from the main plate cylinder.

Almost hairy.

could the internal fins be some sort of secondary emission buster?

Don, don't think it's a guarantee... just typical of the tube??

My reaction to the image when I looked at it last night was that the grids are not wound like the typical tube. They look like they are formed out of a solid bit of metal... sort of like the internals of a ceramic tube.

That would account for their ability to handle the G forces.

...wonder what they did for the heater? 1/8" wide flat nichrome strips?

probably very few failures due to shipping!  ;)

I like it. Wonder how it would do slammed in place of the typical pair of 6146s?
Maybe not enough B+ to make it sing... but a candidate for modulator service??

The GU70 (was that it?) looks like an 845 on steroids...

The Ruskies make some nice toobes!

             _-_-bear

I wonder what that socket is made of. Nice for the price. It's indirectly heated, I like that for ruggedness.

Compare - as seen on the back cover of the April 1958  QST: The RCA-7094!

Looks similar at least in concept.

500 watts CW, 1200vdc, AM phone.

               _-_-bear

It might just retrofit into a SB-220 once the Chinese decide to stop making the 3-500.

Drop the screen from the HV (with some safety circuitry) and change the RF Power meter position to read screen current, the best way to tune a tetrode. The new filament xfmr can do double or triple duty to develop bias as well as relay voltage. The SB-220 fan will keep it happy.

With enough reserve emission it may be very linear.

Hmmmmm  ;D

Carl
KM1H

Think it wants a lower B+ than the 3-500 by quite a bit...?

        _-_-

In a SB-220??

WHY??

Carl

It just dawned on me, this tube is probably rated to 50,000 ft. altitude too; should match one of my surplus transformers.  ;D

And as an additional added attraction, it looks rugged enough to make it through UPS delivery.

....now where did I put those 15E's?...   so cool, some of this old USAF stuff. Hey, probably USAAF for 15E's.

 

you have 15E's as well? Gor any 15R's to go with them?

no, wish I did, 
the E's are brand new/(old surplus) but way back in my career of js hamdom I wanted to see them light up so hooked up a 5v fil. xfor to them.  Glowed pretty and no wear at all what with a volt less than nominal.  But the darn red paint logos turned from bright red to tannish red.

Didn't hurt a damn thing emission wise, but oh well....