>The only crowbar protection that I have seen for HT supplies is that of
>OE5JFL http://www.qsl.net/oe5jfl/flashover.htm . I should imagine that there
>are better (cheaper?) devices out there now.
>
** The most important thing is to limit peak discharge current from the
HV filter capacitor/s. The most fail-safe way of doing this is with a
simple (glitch) resistor in series with the anode supply. However,
during a major fault (big screwdriver short to chassis test) the glitch
resistor must not sustain any damage, either visable or electrical. The
principal value of a glitch resistor is that it lessens the chance of
damage from internal EMForce during an anomaly. Such damage is broken
filaments in 811As and 572Bs. For 3-500Zs it's bent filaments which
result in grid-filament shorts.
-- RE: tube arcs: If a tube arcs due to a contaminant - such as oxygen
and nitrogen molecules (air) - inside the envelope, a subsequent test
with a high-potential tester should show current leakage. Free,
unsolicited advice: If a tube fails, it could be a mistake to assumed it
arced unless a subsequent test with a high-potential tester confirms a
bad vacuum.
- Murphy was right: stuff is usually more complex than we first assume.
>Does anyone know of any other published circuits. I have a couple of pretty
>expensive devices that I would really like to protect.
>
>Regards
>
>Conrad G0RUZ
>
>
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>
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