Quote:
Originally Posted by turretslug
How curious. Could it have been a niche-purpose modulating, gating or level-shifting valve based on PCL85 structure and jigs to minimise initial investment? Perhaps for a mobile (whether land, air or sea) application where 12.6V nominal heater stringing was needed. There were a few weird and wonderful valves cooked up for machine control interface and computer applications, too. We need that time machine!
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I think that this idea is probably closest to the truth, as a lot of developments seem to have been made in the latter valve days for mobile/battery powered valves that could be used on 6/12/24/48 Volt battery supplies and/or be very rugged, these being apparently modifications to standard types in order to save tooling costs especially where the production run was not very high.
A centre tapped heater of 6.3/12.6 Volts suggests to me an ECC81/2/3 heater setup were you wire in series (across the ends) for 12 Volt and parallel (between CT and ends) for 6 Volt supply. I believe that 6 volt batteries were still being used on vehicles at that time (and still are?).
I will not hazard a guess as to the actual intended use for this oddball, suffice to say that as the world of electronics applications was expanding rapidly during that time, it could be almost anything. Only one real clue here, it must have been something worthwhile (or high budget military?) to interest a company like Mullard/Philips . . .
I would forget the amateur radio connection, that is probably just a red herring.