Russki GM-70 tube

[W7TFO]

Has anyone tried these at RF in place of the 211-242C triode?

73DG

[k4kyv]

They operate at 20v on the filament instead of 10v, but at nearly the same filament current, so with twice the filament power they should have better peak emission.  Looks like it might be a good tube, if quality control is good enough that it would have a good life expectancy. At the price, you couldn't go wrong ordering a pair and trying them out. According to the specs, it looks closer to an 845 than to a 211.

From the pix, it looks like it uses a different socket from the 211 and 845.  Maybe a socket like the 8008 MV rectifier?

The 845 was never recommended by RCA for RF service, though.  It is primarily a low plate resistance class A audio tube. If the GM-70 is really what it is cracked up to be, it ought to be an audiophool's wet dream.

[W7TFO]

Indeed.  There are many HI-FI amplifier designs using the GM-70 on the web today. 

These are all USSR ex-military production and are very uniform and are high quality in construction.

The tube takes a socket a lot like the "Westinghouse" 4-pin jumbo (8008), but the spacing is different.  One pin is larger, and requires the enlargement of the corresponding hole in a US large septar socket by using a tile bit.

Now proper wafer sockets are available, and I'll be trying out a circuit with two of them.

These ought to be a beautiful driver for 833's in class "B" modulator service.

73DG

[k4kyv]

The specs don't indicate the plate resistance, but with the low mu and high current rating, it's probably low. Tube life rated at 1000 hours, but should last much longer than that.

It's been a long time since I had heard tungsten called "wolfram" (hence the symbol W in the periodic chart).

http://scottbecker.net/tube/sheets/084/g/GM70.pdf