The CV2128 is a UK government specification valve, it appears to be a direct equivalent of the commercial ECH81.

This triode heptode was designed for the role of frequency changer (mixer) in superhet receivers, the two valves share a common cathode. The triode is to be used as the local oscillator feeding the 13 Volts amplitude sine wave to the heptode mixer. Within the heptode, non linear operating causes the signals to interact to produce in the anode waveform the following major frequencies: signal, LO, signal + LO and signal minus LO. The anode circuit is tuned to enhance one of these signals, normally signal minus LO. For radio reception at the time an intermediate frequency of 455KHz would be typical.

Although badged with only a CV number, the ridges moulded in the top of the glass envelope suggest that it was made on a Philips-Mullard production line.

The thin glass tube envelope is 20 mm in diameter and the valve is 58 mm tall excluding the B9A base pins.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9
	g2-g4	g1	k-g5-s	h	h	a	g1	a(t)	g(t)

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	mAa
	6.3	0.3	100	13

Heptode	Va	Vs	Vg	mAa	mAs	ra	gm
	250	250	-2	6.5	3.8	0.7M	0.775

This exhibit was last updated on 31 January 2004