This Mazda second-generation double-diode-pentode was (we think) redesigned as a double-diode beam tetrode during the latter part of its production life. The picture shows a valve of relatively late manufacture.

The PenDD4020 had rather better gain than the Pen453DD and was correspondingly more successful, being used in a good number of AC/DC Murphy sets from around 1936 onwards. A good valve but, interestingly, its eventual end of life was often due to failure of the diode cathode emission rather than weakness in the pentode section.

The classic envelope is 51 mm in diameter and, excluding the B7 base pins, is 124 mm tall.

 
Pin Connections

B7	1	2	3	4	5	6	7	tc
	a(d2)	a	a(d1)	h	h	k	g2	g1

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	gm	Pout	D
	40	0.2	240	250	-7.75	43	8.5	7.8	3.9W	7%

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 02 December 2007 {find valves by name}