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PJL · 20th Jan 2020, 10:18 pm

I think the Puratone Rubon valves were only manufactured in 1924 but maybe they were branding as there are quite a few different types there. The Mullards will be later, the PM22 is a pentode so at least 1928. They are all dull emitter (that's what DE stands for), probably date to no later than 1930, and we may struggle to find any data for the Rubon valves. A simple resistance check of the filament is all that is needed for testing.

20th Jan 2020, 10:18 pm	#15
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: DE5 valves plus others, of any interest? I think the Puratone Rubon valves were only manufactured in 1924 but maybe they were branding as there are quite a few different types there. The Mullards will be later, the PM22 is a pentode so at least 1928. They are all dull emitter (that's what DE stands for), probably date to no later than 1930, and we may struggle to find any data for the Rubon valves. A simple resistance check of the filament is all that is needed for testing.