The EC91 is a miniature single triode. The Mullard manual describes the EC91 as a miniature screened triode for use as a grounded grid amplifier.
Mullard also produced the M8099 special quality version for critical applications.
This type of valve was designed for RF applications at VHF up to a maximum frequency of 250 MHz. These would include radio, television and radar. The equivalent noise resistance was given as 400 Ohms.
The triode is the central box. The strips either side of the triode are just supports. Note the screen below the lower mica.
Here the bright support strips are in the centre. The control grid is on copper supports and has a cooling fin at the top. The anode has side flanges for fixing and heat dissipation.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 46 mm tall.
