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Alex Pogossov Alex Pogossov is offline
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Default Overvoltage protection


"Phil Allison" wrote in message
...

** Cos the usual RC network suppresses the spike sufficiently, along with
the load.


If a load is connected -- correct. If no load, then as I have mentioned you
need microfarades + several kiloohms to absorb it, not a few nanofarades
usually connected to dump HF ringing of the leakage inductance.


Or is the assumption that no one will be changing tubes on a working amp?


** Well, not with no load connected.


What about an amp being fool proof then?

Or occasional arcing and sparking is not a problem?


** The Aussie made 6V6GT used in my first valve amp liked to spark
internally with no load. Never did it, the A&R OP tranny or the socket any
permanent harm. But if you wanna go belt and braces - fine with me....

BTW - how much HT have you got ??


Only 250V. But I do not want to risk any possibility of insulation breakdown
in an old lousy OPT.
Probably a small varistor rated at 350...400Vdc and with less than 500pF of
capacitance will be OK.

The tread is also of general nature -- why do not we see varistors in the
tube amp circuits. Probably you are right -- no one suffered serios damage
of this particular stress mode.