Quote:
Originally Posted by Heatercathodeshort
I have often wondered if the 'EF91' or rather the Mazda version of it the 6F12 was actually designed by Mazda themselves rather than the Mullard version.
The 6F12 appears in a number of post war television receivers including the 1947 Ultra W470. The actual Mullard EF91 does not seem to appear until 1949, an early user being Ferguson with their 941T.
I think the 1946 PYE D16T must be the earliest use of the EB91 in the UK.
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Who first developed the EF91/Z77/6F12/8D3 valve is an open question. My best estimate is that the Osram Z77 was the parent valve, see:
https://www.vintage-radio.net/forum/...1&postcount=60.
Cheers,