Tom said:
>Not quite a peer reviewed engineering text is it Will?<
He does tell you not to leave grids open, though.
When you have grid current, you have grid dissipation. Which is why tubes
designed for Class C had carbon coatings or whatever to reduce emission. See
the RCA TT4 Tube Manual. It's fair to say that flash over dumping a lot of
current into the grid could well heat it enough to get emission.
Whether 'arc' is the right term is arguable, in that 'arc' implies a plasma
effect, which you don't get in a vacuum. However, 'flashovers' in high power
tubes with a good vacuum have been written up many times over the years, with a
number of explanations. In tube manufacturing circles, they were said to be
'barnacles', and could be removed by controlled energy flashovers - there was
an article in about 1934 in the IEE journal. As I recall, flashovers are more
prevalent with new tubes.
Sorry, I just don't buy grid fuses ( and even more so, resistors as fuses) as a
good idea. I believe I'm not the only one, though.
73
Peter G3RZP
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