The 7R7 is a screened pentode and double diode. THis is the classic valve design for AGC rectification, signal detection and first audio amplifier. One would expect to see a variable μ design if the high impedance pentode was for IF amplification.

The type designation is etched into the envelope dome. There is no make identified.

The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 55 mm tall. The metal skirt is 30 mm in diameter.

 
Pin Connections

B8B	1	2	3	4	5	6	7	8
	h	a	a(d2)	a(d1)	g2	g1	k	h

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.3	250	100	-1	6.2	1.6	1M	2.3

This exhibit was last updated on 15 January 2008