The EL38 was designed, in the late 1940s, as a television line output stage valve. In the early days of CRT based television the tubes could have been either electrostatic or magnetic deflection. The EHT supplies were mainly derived from special mains transformers and ran at about 10 - 14 kV. Thus the line output valve was not as heavily stressed as later types had to be.

The EL38 was designed to withstand a positive anode surge of 8,000 Volts and in addition to the 25 Watt anode dissipation the screen grid was wound to withstand a dissipation of 8 Watts.

The cathode is oval, and the ceramic insulators are clearly visible. The control grid is wound with fine gold plated wire and is supported on copper rods to aid heat conduction. At the top of the grid support rods are two grey radiator fins. The second grid is of increased pitch but close to the control grid. The outer suppressor grid is a lazy spiral of bright wire not far from the inside of the anode cavity.

The classic envelope is 41 mm in diameter and, excluding the IO base pins, is 120 mm tall.

References: Datasheet & ¹⁰⁴⁰. Type EL38 was first introduced^¶ in 1946.

 
Pin Connections

IO	1	2	3	4	5	6	7	8	tc
	g3	h	-	g2	g1	-	h	k	a

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	mAa	mAs	Pdiss
	6.3	1.4	300	250	64	18	25W

Thanks to Frank Philipse for supplying the above PDF datasheet

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