The ECC35 is described by Mullard in 1957 as a high gain double triode with separate cathodes for use in paraphase AF voltage amplifiers. In 2008 it is much sought after for use in audio amplifiers

The side view shows two triode sections between mica discs. The anodes are dark to radiate more heat and a small central oval anode space is augmented by side flanges that have notch fixings to hold the two plates together and to clamp to the support rods. Also visible are the connections from the pinch to the rest of the electrodes.

In close-up the points on the top mica can be seen to be bend down as they grip the glass envelope to hold the internal components rigid. The grid of each section is wound on copper rods and to further aid heat dissipation one of the grid rods of each valve has an attached radiator fin. The cathode is formed on a cylindrical base tube. The method of anode plate clamping is also clearer. On one plate a hole is formed and on the opposite plate a U shaped lug is formed by cutting on three sides. The final assembly process on the anode forming machine, pushes the lug into the hole and folds it over to form the fixing.

The wide glass tube envelope is 30 mm in diameter, and excluding the IO base pins, is 69 mm tall.

References: Datasheet, ¹⁰⁴⁰, ¹⁰⁴³ & ³⁰⁰². Type ECC35 was first introduced^¶ in 1942.

 
Pin Connections

IO	1	2	3	4	5	6	7	8
	g1(2)	a(2)	k(2)	g1(1)	a(1)	k(1)	h	h

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	ra	gm	μ
	6.3	0.4	250	-2	2.3	34,000	2.0	68

Thanks to Frank Philipse for supplying the above PDF datasheet

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