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Old 11th Oct 2022, 4:49 pm   #9
cathoderay57
Nonode
 
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,358
Default Re: Hmv 650

Just found these pages at the Valve Museum, which I didn't know existed. It turns out that American equivalent valves including 6F6G (=KT63), 6J7G (=Z63/KTZ63), 6L7G (=X64) were around in 1936 http://www.r-type.org/inx/inx1936.htm but the Marconi numbers used in this set do not seem to have appeared until 1937 http://www.r-type.org/inx/inx1937.htm and so Paul is probably right Cheers, Jerry
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