The EBF89 features two signal diodes and a variable μ pentode in the one envelope and sharing a common cathode. The diode anodes are small plates placed either side of an extended cathode tube.

The variable μ characteristic is indicative of a device designed to have its gain controlled by an AGC system. This places this valve in service as a final IF amplifier and detector. Or with a separate detector the two diodes can provide a delayed AGC voltage. This would give full amplification until a threshold is reached. The high impedance of the pentode supports the case for use with a tuned circuit connected to the anode.

The thin glass tube envelope is 20 mm in diameter and excluding the B9A base pins the valve is 57 mm tall.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9
	g2	g1	k,s	h	h	a	ad(1)	ad(2)	g3

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.3	250	100	-2	9	2.7	1M	3.8

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 10 June 2007 {find valves by name}