[Synchrodyne]

The EF80 certainly made full use of the noval (B9A) base. This allowed an RF pentode to have a separate suppressor grid pinout, two cathode pinouts and a separate internal screen pinout.

The Rimlock (B8A) base was more restrictive. The EF42 had one cathode pinout, along with separate suppressor grid and internal screen pinouts. The Mazda 6F13 was the same. The 6F1 was an improved 6F13, with two cathode pinouts. As it retained the Rimlock base, the compromise was to assign the suppressor grid and the internal screen to the same pinout.

Perhaps a useful question here is: did Philips anywhere use the noval base and its associated envelope diameter for valves that could have been accommodated on the B7G base and its associated envelope diameter?

The answer appears to be “maybe”, but if so, it was rarely so. The same question for the Rimlock base would produce a definite “yes” answer, as shown by the EB41/UB41 case.

The valves in the initial noval Radio series and the initial noval TV series either required more than 7 pinouts (e.g. ECH80, EF80, ECL80, ECC81, etc,) or, where they did not require more than 7 pinouts, required the larger envelope diameter associated with the noval base (EL80, PL82, PL83, etc.). The noval envelope diameter was close to that of the Rimlock type, and in the latter case it had been sized to accommodate a 9 W anode dissipation output pentode, which was thought to be beyond the reasonable capability of the B7G envelope diameter. The one valve associated with both series that did not require either more than 7 pinouts or the larger envelope was the double diode, and in this case Philips chose to use the EB91 with B7G base, rather than develop a corresponding noval type.

The FM-AM radio series of the early 1950s, as well as adding necessarily-noval valves such as the ECH81 and EABC80, also included the EC92 VHF triode for FM front end applications, Philips not yet having adopted the ECC85. The EC92 required 6 pinouts (including a separate pinout for its internal screen) and was on the B7G base. On the face of it, this is evidence that Philips was prepared to drop back from the B9A to the B7G where the latter was fit for purpose. Actually, there might have been a simpler explanation. The EC92 was the European version of the American 6AB4, introduced by GE in 1949. as being half of the 1947 12AT7. It was probably easier to clone the 6AB4 than to develop a new valve, possibly noval. Given that the ECC81 was the European version of the 12AT7, then the EC92 was half of an ECC81. As an aside, with the 12AT7/6AB4 (ECC81/EC92) pair, the 12AT7 came first, the opposite of the case with the 12AU7/6C4 (ECC82/EC90), where the 12AU7 came first.

B7G bases were also used for the car radio RF pentodes, EF97 (remote cutoff) and EF98 (sharp cutoff) of the mid-1950s. These appear to have been Philips (or perhaps other European valvemakers) developments, and not clones of American prototypes. In both cases the internal screens shared a pinout with the cathodes. Possibly the B7G base and envelope was chosen here because compactness was a virtue in car radio chassis.

Looking towards industrial applications, one may consider the EC80 and EC81, both of 1949 and both novals. The EC80 was a UHF grounded grid triode amplifier or mixer, for use up to 600 MHz. It had four grid pinouts, so required 8 pinouts in total.

The EC81 was a UHF triode oscillator for use up to 1500 MHz, and constitutes the one “maybe” in this simple analysis. It had one grid pinout, so 5 in total. It probably could have been fitted on the B7G base. Still, the B9A base probably allowed wider spacing between the cathode, grid and anode pins, and so lower interelectrode capacitances. Anode dissipation was 3 W, I think well within B7G envelope capacity, but perhaps the larger B9A envelope conferred smaller temperature variations and so better stability. So, there might have been technical reasons for using the B9A base and envelope. Otherwise, commonality with the EC80 was probably a reason. (Both valves were described in Philips Technical Review 1949 September.)


Cheers,