The Mazda 215SG is a screen grid valve or tetrode. It was designed for RF amplification in radio receivers. The screen provides isolation between the grid and anode circuits and enables greater individual stage gains to be achieved without instability.

The other side of the envelope is not silvered and the electrodes are visible. Note the rectangular anode and concentric grids whilst still having the bakelite top cap assembly of the early 1930s.

The classic envelope is 42 mm in diameter, and excluding the B4 base pins is 110 mm tall.

 
Pin Connections

B4	1	2	3	4	tc
	g2	g1	f	f	a

 
Absolute Maximum Operating Conditions

Tetrode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm	μ
	2.0	0.15	150	80	-1.5	7.0	-	0.3M	1.1	330

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 12 June 2007 {find valves by name}