The EABC80 is a triple diode triode. The triode and two diodes share a common cathode but one diode has a separate cathode.
This exhibit is of British manufacture, another example EABC80 is labelled Foreign.
The EABC80 was specifically designed (1954) for use in the detector stage of early FM and FM/AM radios. The triode section providing the first audio amplification, the single diode and one of the diode pair were used as an FM detector in a ratio detector circuit. SeeFM Broadcasting and Signal Detection. The other diode in the pair being used as the AM detector when that part of the circuit was required.
This design was also produced in versions for universal sets (no mains transformer). SeeUABC80 and PABC80.
The triode anode is carbonised to radiate heat efficiently and the grid is wound on copper support rods. The heaters connect at the top and are supplied by the two risers seen on the left.
The distinctive three tower structure. The diode anodes are screened by the bright boxes.
The screening box is made more rigid by the pressed ribs.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 59 mm tall.
References: Data-sheet, 3002 & 1040. Type EABC80 was first introduced in 1952. See also1952 adverts.