wrote:
>>>
>>> ... by stopping the flow of current into the screen PS.
>>>
>> If the "glitch" is an arc from anode to screen, the mains fuse won't
>> protect the screen at all.
>
>A tube that arcs from the anode to the screen is already a goner, Ian,
>so there is nothing of value to protect.
That simply isn't true. Well designed power supplies can protect the
tube, the anode supply and the screen supply against a wide range of
faults, including arcs. Many of these faults are completely recoverable.
On the other hand, if someone believes that "a tube that arcs from the
anode to the screen is already a goner" then it's easy to build an
amplifier that will make it come true.
> Common reasons for high dissipation in the screen are loss of load,
>loss of anode supply, and mistuning.
>In all such cases a fast-acting fuse suffices.
Yes, those are some of the common reasons for high dissipation... but
that isn't the only case you need to protect against.
Also, DXers and contesters don't want to fool with fuses. If the fault
is not fatal - which it very often isn't - they need the amp to come
back online with a touch of a button.
Finally, please let me emphasize that I am not pushing a commercial
product here. This is simply the design approach that I believe in,
because it works.
--
73 from Ian G/GM3SEK
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