This is a giant tube. With around 500 grams of weight, definitely this is a heavy weight class. It’s a Pentode with shadow grid to reduce the screen current – so we should call it a Hexode. Its filament rated at around 12.5V and 2.3A. At around 25W filament, it shouldn’t be that hot.
As shown below, the filament is on the center, from the top to bottom. The metal plate on the base seems used as heatsink. This tube is very sturdy in terms of the construction.
The close up shoot on the filament and the grids.
It comes in an original but rotten box. The smell itself could explain the age of this tube.
The serial number still there. I admire the way those old factory handles the tube. It’s more to an art rather than a glass that massively produced.
Inside the box. The foam to protect the tube and make sure it’s safe in a long distance transportation.
The tube construction in close up. I have nothing more to say, this is a really serious and well made tube. Up to 250W plate dissipation.
The metal base itself seems used as heatsink. After 10-15 minutes photo session, I can feel the warm temperature on this metal base.
The pins are very big. My alligator clips definitely can’t be used. So I use old trick with tin solder (too lazy to use copper wire). Few rounds on the pin, then here you go!
Another shoot from the side of the tube. The construction is quite complicated (well, it’s a Hexode, remember?). The materials also look thick and heavy. Not mentioning the glass is also quite thick.
Comparison between several popular tubes: EL34, 2A3, 300B, VT-129/304TL, then this Telefunken YL1260 (from left to right).