Thread: 6SK7 and 6SK7W
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Old 13th Feb 2021, 11:12 am   #8
marty_ell
Triode
 
Join Date: Aug 2008
Location: Marlborough, Wiltshire, UK.
Posts: 44
Default Re: 6SK7 and 6SK7W

Quote:
Originally Posted by usradcoll1 View Post
Another interesting thread!
I was thinking about the "Y" suffix on some metal valves. It meant a low loss mica filled yellow molded base. They were intended for high frequency use. 6SB7Y and several others. The "Loctal" valve was also intended for that application. And then, there's the Acorn valve!
Dave, USradcoll1
6SJ7Y with its mica filled base was notably used in the BC-221 heterodyne Frequency Meter. I restored the -AF version one of these many years ago and debugged it with a standard 6SJ7. The eventual fitting of the Y improved a reasonably stable unit to a quite incredibly stable and accurate unit, quite good enough for amateur h.f. work even today (although tedious to use compared to modern digital's).

I love acorn valves ! As a youngster I played with the 954/5/6/7 and Marconi/Osram/MOV HA1 in various radio projects. I was particularly attracted to their tiny size, so also used them to make a very physically small audio amplifier - the only one attempted as far as I know. I gave up working with them when UHF valve holders became unobtainable at pocket-money prices (pre-Internet days).

Cheers, Marty
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