Hi Rich,
Yes, of course, a faster dump means more peak current - that is my concern. The
10 ohm
resistor and the components/wiring in series with it will experience a peak
current ~3.6 times
greater than with the 36 ohm resistor. At what point do I become concerned?
IOW, what is
the optimum value for the glitch resistor all other things (surge capacity)
being equal? I think
Ian recommends (as a rule of thumb) something like 20 ohms per/KV on his
website.
Thanks!
Mike, W4EF..........
----- Original Message -----
From: "2" <2@vc.net>
To: "Mike" <W4EF@dellroy.com>; "@AMPS" <amps@contesting.com>
Sent: Sunday, September 09, 2001 8:13 PM
Subject: Re: [AMPS] SB-1000 mods?
> >
> >Hi Rich,
> >
> >Would there be any concern about the lower maximum resistance
> >dictated by the use of
> >the 5 watt steady-state rating versus using a 20 or 50 watt resistor? At
> >750mA
>
> // The power supply is not able to do 750mA continuous. Average
> duty-cycle on SSB is c. 15% - CW is c. 30%.
>
>
> >worst case steady-state anode current, the maximum resistance that
> >could beused with the 5 watt resistor would be ~9 ohms
> >,
> // The lowest value made is 10-ohms.
>
> >whereas at 20 watt resistor could be set as
> >high as 36 ohms
> >assuming the same steady state anode current. Seems like the smaller
> >resistor would allow
> >the charge in the filter caps to dump much faster than the larger
> >resistor,
>
> // A faster dump means more peak current.
>
>
> >or are there other factors that dominate the discharge time (capacitor
> >ESR, stray inductance, etc).
>
> ESR adds perhaps a few ohms.
> >
> cheers, Mike
> >
> >----- Original Message -----
> >From: "2" <2@vc.net>
> >To: "Mike" <W4EF@dellroy.com>; "@AMPS" <amps@contesting.com>
> >Sent: Sunday, September 09, 2001 4:11 PM
> >Subject: Re: [AMPS] SB-1000 mods?
> >
> >
> >> >
> >> >Looks like the RCD resistors will do the trick (the 20W parts should
> >> >fit nicely in the space available inside the L-7 PS). ... ... ....
> >> >
> >> Their 5Watter (140 watt-seconds/joules) will do an L-7 with ease
> >> since stored energy is c. 80-joules. If you get a price, please post it.
> >>
> >> cheers, Mike.
> >>
> >> >----- Original Message -----
> >> >From: "Tom Rauch" <w8ji@akorn.net>
> >> >To: <amps@contesting.com>; "Mike" <W4EF@dellroy.com>
> >> >Sent: Saturday, September 08, 2001 12:35 PM
> >> >Subject: Re: [AMPS] SB-1000 mods?
> >> >
> >> >
> >> >> > glitch resistor? I have some 25 ohm/25 watt Dale RER type
> >> >> > metal body resistors, but I am concerned that they might be
> >> >> > due to the relatively small gap between the leads and the metal
> >>>>> prone to flash over case.
> >> >> > Presumeably a ceramic body wire wound resistor is the way to go.
> >> >> > Should I be concerned about inductance (L*di/dt kick) - some
> >> >> > wirewounds seem to be classified as "non-inductive" whereas some
> >> >> > aren't?
> >> >>
> >> >> The resistor must be surge rated for the voltage across the resistor
> >> >> and the peak energy.
> >> >>
> >> >> RCD makes xxx-P series pulse rated resistors, or you can use a
> >> >> "glow-bar" type. The RCD pulse rated resistor barely costs more
> >> >> than a conventional wire wound resistor.
> >> >>
> >> >> It makes no difference at all if it is inductive, because the
> >> >> inductance will be negligible. Many non-inductive wire wound
> >> >> resistors have a lower than normal voltage rating (from lead to
> >> >> lead), because of the winding method.
> >> >>
> >> >> The metal case resistor won't work well.
> >> >>
> >> >>
> >> >>
> >> >>
> >> >>
> >> >> 73, Tom W8JI
> >> >> W8JI@contesting.com
> >> >
> >> >
> >> >--
> >> >FAQ on WWW: http://www.contesting.com/FAQ/amps
> >> >Submissions: amps@contesting.com
> >> >Administrative requests: amps-REQUEST@contesting.com
> >> >Problems: owner-amps@contesting.com
> >> >
> >> >
> >>
> >>
> >> - R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.
> >> end
> >>
> >
> >
> >--
> >FAQ on WWW: http://www.contesting.com/FAQ/amps
> >Submissions: amps@contesting.com
> >Administrative requests: amps-REQUEST@contesting.com
> >Problems: owner-amps@contesting.com
> >
> >
>
>
> - R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.
> end
>
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