The PABC80 is a triple diode triode specifically designed for the detector stage in AM/FM receivers. This valve is designed to operate in a 300 mA heater chain directly across the mains. The UABC80 differs only in the heater rating, whereas the EABC80 was designed for the higher anode voltage found in designed with transformer derived HT as well as a 6.3 Volt heater.
Normally this valve featured in a ratio detector circuit for FM demodulation and a diode detector for AM as well as the first stage of audio amplification. SeeFM Broadcasting and Signal Detection.
The three sections have the same external dimensions. One houses the triode, one the double diode and the third the single diode. The boxes of the diodes are connected as screens.
The triode is on the right and the control grid is visible through the hole in the side wall of the anode. The vertical pieces in the centre carry the heater connections to the top of the valve where the heaters are connected in parallel.
Face view of the triode. The heater risers are shaped to give rigidity to the thin tape.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 58 mm tall.
References: Data-sheet & 1040. Type PABC80 was first introduced in 1952. See also1952 adverts.
