ECH81+EF80 (or 85 or 89)+ EBC81 (or 91)+ EL84 (noval Socket) + rectifier and magic eye indicator (depending on the radio class and manufacturer). AC/DC sets without mains transformer would use "U" tubes of the same types, e.g. UCH42+UF41+UBC41+UL41+UY41 rectifier. There was also a tube with a double diode and a triode sharing a common cathode, and an additional, independent single diode section, named EABC80 or 6AK8 or 6T8 (with a shorter glass envelope) and its versions for AC/DC transformerless receivers with series heater chains, named PABC80 (9AK8, 300 mA for TV sets), HABC80 (19T8, 150 mA for radios) and UABC80 (27AK8, 100 mA for radios). This tube was designed for early AM/FM (MW/VHF) radio sets and was widely used until the end of the tube era; the double diode was used for FM demodulation, the third, independent diode for AM detection and/or automatic gain control (AGC). The main configurations for an early tube AM/FM set using EABC80 in the 1950s and '60s were: EC92+EF80 (or 85 or 89)+ECH81+EF80 (or 85 or 89)+EABC80+EL84 (or 95) -or- ECC85+EF80 (or 85 or 89)+ECH81+EABC80+EL84 (or 95)+ rectifier (tube or solid state) and indicator, depending on the radio class and manufacturer. For AC/DC radios, UCC85+UCH81+UF80 (or 85 or 89)+UABC80+UL84+ rectifier and indicator. These configurations were kept until semiconductor (germanium) diodes became available, making this type of tube obsolete. References RCA Receiving Tube Manual, Series RC-12, RC-19, RC-25 - Published by RCA. Vacuum tubes