R: [AMPS] Load C as last resort safety

[Maurizio Panicara]

Generally speaking (I don't know the SB200), more than something looks
incorrect in the assumptions of the original message.

No engeneer, unless insane, would sign the project of an amplifier
without a properly dimensioned coil paralleled to PI output and without
conventional fuses or breakers in the PS.
Anyway, not all of the load capacitors spark because of HV, I've seen
and built a number of PAs using vacuum variables in order to have a big
capacitance range in a small space but they withstand DC easily.
If the amplifier is correctly designed, not a part of the circuit but a fuse
or a breaker must blow when a short or an abnormally high current drain
occurs,  KU7I must be safe in any case.
The only resistor of such value I can image along the Hi voltage line is
that used in the supply to limit  the inrush current when the filter
capacitor charges, definitely it's not a fuse in this case too.

73,
Mauri I4JMY


-----Messaggio Originale-----
Da: <zeitler@ibm.net>
A: Rich Measures <measures@vcnet.com>; steve thacker <kb5vca@cei.net>;
<amps@contesting.com>
Data invio: mercoledì 11 agosto 1999 18.14
Oggetto: [AMPS] Load C as last resort safety


>
> Others have written:
>
> >>the rf safety choke is there for a definite safety reason---to blow from
> the
> >>dc supply gitting thru the plate blocking cap--check it--bet it shorted.
> >>new call w5set.
> >
>
> And then Rich added:
>
>
> >When the DC blocker fails without a "safety choke" being present, the
> >Load C itself acts as a protective spark gap, arcs,  and shorts the HV to
> >ground.
>
>
> My question: How long would it take a 10 ohm 10 watt high voltage safety
> "fuse" that is in the B+ line to open in the event the plate bypass cap
did
> short and the load C saw the full anode potential?
>
> Just curious. Wonder how dangerous this is to the operator other than the
> gun shot loud POP that happens when the resistors open scaring the hell
out
> of the unsuspecting ham (in this case Ku7i).
>
> Lane
> Ku7i
>
>
>
>
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>






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