The AC/TP is a triode pentode that was designed as a frequency changer for broadcast radio reception.

The black markings on the metalisation indicate a model from the later end of production, possibly 1940s

The triode oscillator would have to generate 3 Volts peak to peak. The pentode, operating in a non linear mode, would be the mixer. The input signal would be applied to the top cap of the valve and this would provide some isolation from the oscillator circuit.

The outer metalisation hides the inner construction.

The balloon envelope is 43 mm in diameter and, excluding the B9 base pins, is 106 mm tall.

 
Pin Connections

B9	1	2	3	4	5	6	7	8	9	tc
	g2	a	g3	h	h	k	at	gt	m	g1

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	4.0	1.25	250	200	-5	6.5	2.5	0.9M	0.7

Triode	Va
	150

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 05 July 2007 {find valves by name}