20D1 @ The Valve Museum

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20D1

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Valves and their Habits

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Mazda The Communications & Electronics Museum Trust Other 20D1 exhibits

The 20D1 is a double signal diode with separate cathodes. Possible uses would be demodulation of signal and AGC voltages. The 200 mA heater requirement indicates universal mains sets with series heater chains.

Our other 20D1 has the newer style of lettering.

Two diode sections separated by a plate for the electrostatic screen..

The anode plates are stitched together either side of the central indirectly heated cathode.

The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 45 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type 20D1 was first introduced in 1949. See also 1949 adverts.

Pin Connections

B7G	1	2	3	4	5	6	7
	k(1)	a(2)	h	h	k(2)	s	a(1)

Absolute Maximum Operating Conditions^¶

Diode	Vh	Ah	Va	mAa
	9.5	0.2	175	9

Thanks to Frank Philipse for supplying the above PDF datasheet.

Updated November 13, 2025.

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