Comments on: The Nearest Book Meme http://www.scottharney.com/2006/10/31/the-nearest-book-meme/ Notes about life, *nix, and other stuff. Thu, 21 Aug 2008 19:39:15 +0000 http://wordpress.org/?v=2.0.11 by: Mike Fowler http://www.scottharney.com/2006/10/31/the-nearest-book-meme/#comment-238 Wed, 29 Nov 2006 03:21:45 +0000 http://www.scottharney.com/2006/10/31/the-nearest-book-meme/#comment-238 The use of higher voltages results in some good valves being classed as filament-to-grid short circuits. With a.c. supply, it is usual to design the circuit so that resistances over 0.5 megohm do not indicate as shorts; this is to avoid capacitance effects. With d.c. supplies there is no similar limitation, but different models vary considerably in their shorts testing sensitivity. The most satisfactory switching arrangement is one which tests for shorts from any pin to all other pins tied together. The circuit of Fig 3.4 may be used, except that the cathode need not be heated. (RCA Radiotron Designer's Handbook, 4th Ed. (c)1952) The use of higher voltages results in some good valves being classed as filament-to-grid short circuits.

With a.c. supply, it is usual to design the circuit so that resistances over 0.5 megohm do not indicate as shorts; this is to avoid capacitance effects. With d.c. supplies there is no similar limitation, but different models vary considerably in their shorts testing sensitivity.

The most satisfactory switching arrangement is one which tests for shorts from any pin to all other pins tied together. The circuit of Fig 3.4 may be used, except that the cathode need not be heated.

(RCA Radiotron Designer’s Handbook, 4th Ed. (c)1952)

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