Quote:
Originally Posted by G6Tanuki
The mid-1960s was also the time when the industry was switching from germanium to silicon transistors (and generally from P-N-P to N-P-N as well with a change in which supply-rail was 'earth') so I can easily imagine how a small manufacturer with limited development funds would want to keep as much of their existing design in production and graft in only the bare minimum of what they needed to UHF/625-line-ize it.
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I think there was also a tendency to have collector-circuit directly grounded in some UHF tuners (AF239/BF180 etc. collector to stripline and the like)- presumably there were doubts about decoupler effectiveness? Thus, an AFxxx equipped tuner might have negative-to-earth and BFxxx positive-to-earth. I'm sure I recall cases of NPN tuners relying on being screwed to wooden cases seperately from the main chassis.