The 1625 is electrically identical to the 807, except for the heater requirements and base cap. At 12.6 Volts the 1625 would have been designed for mobile equipment.

The parameters given are for single ended use. When used in a class AB1 push pull pair with 600 volts on the anode an output power of 65 Watts was normal.

These valves were much used in medium power amateur radio transmitters for high level modulation. In this use the output transformer, called a modulation transformer, would be impedance matched to the anode circuit of the RF power valve. The audio power would increase or decrease the amplitude of the RF envelope.

The 807 itself was a workhorse of the HF bands. As a transmitter power amplifier (shown in the lower table) operating in class C producing 40 Watts of RF, it would need a pair of in push pull to generate the 20 Watts of audio required to fully modulate the valve. Other modulation systems operating on the screen grid would require much less audio drive but with less RF output.

The classic envelope is 48 mm in diameter and, excluding the UX7 base pins, is 128 mm tall.

 
Pin Connections

UX7	1	2	3	4	5	6	7	tc
	h	nc	g2	g1	nc	k-g3	h	a

 
Absolute Maximum Operating Conditions

Beam Tetrode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm	Pout
	12.6	0.45	300	250	-14	83	8	20k	6.5	6.7W

Beam Tetrode	Va	Vs	Vg	mAa	mAs	mAg	Pdriv	Pdiss	Pout	freq	f.max
	600	250	-45	100	7	3.5	0.2W	25W	40W	60	125

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 12 June 2007 {find valves by name}