Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
Yes, absorbing reading, and it helps to emphasise what sophisticated and precision components valves really were.
The article on innoval valves and the Rimlock-like fritting process reminded me about a UL41 in employment here, with its straight, shoulderless bulb- perhaps a late-production type and which, apart from its B8a base and small keying pip, could at first glance be taken for something like a UL84. Could it be that this overall diameter increase of around 2mm helped keep the temperature of this often hard-worked type reasonable, or maybe it simply meant that legacy B8a valve types could be processed with B9a jigs. I gather that there was a "middle-age spread" version of the PL81 with an expanded-diameter bulb section, supposedly to help reliability of this also hard-working valve.
(Excuse focus on this ad-hoc smartphone shot!)
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