It's the safety issues that worry me most of all. Having been through the mill
of UL, CSA, CE etc when designing products for sale, I know it is a complex
subject and common sense does not always lead to a safe solution, ie you need
hard knowledge like creepage and clearance distances, insulation breakdown etc.
David
G3UNA
>
> From: "Roger" <sub1@rogerhalstead.com>
> Date: 2008/01/03 Thu AM 02:20:10 GMT
> To: <amps@contesting.com>
> Subject: Re: [Amps] HV Supplies and Diodes
>
>
>
>
> >I find it a bit strange and somewhat comical that the only ones that appear
> > to champion resistors and capacitors across any series string of 1N540x
> > diodes is the amateur community.
> >
> > Not one manufacturers application notes mention them.
> >
> > No industrial product that Im aware uses them.
> >
> > The one ham amp manufacturer mentioned has a reputation of power supply
> > problems.
> >
> > Most of us realize that the diodes of the 60's had problems but is there
> > any
> > reason to continue it almost a half century later?
> >
> > Fact or mythology?
>
> Neither. It's History and background. Most of the current crop of hams have
> been around long enough that's "the way things were" and unless a person
> keeps current they will still tend to think in the way they were taught.
> Early on we might build a PS. The last one I built was close to 30 years
> ago when diode strings were big stacks of diodes, resistors, and caps as
> were the "potted" commercial replacements for vacuum tube rectifiers. I
> think you will find well over half the hams around now still think in the
> same terms. Also take a look at the diode stacks on all but the more recent
> amps you are likely to find in most stations. The only amp I own that is
> less than 20 years old is my new solid state Tokyo Hy-Power HL1.5Kfx.
> That's why I deferred my comments to the "Handbook". IOW, check the
> "Handbook" for proper design.
>
>
> Roger (K8RI)
>
>
> >
> > Carl
> > KM1H
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Jim Tonne" <tonne@comcast.net>
> > To: "Dennis W0JX" <w0jx@yahoo.com>; <amps@contesting.com>
> > Sent: Wednesday, January 02, 2008 2:20 PM
> > Subject: Re: [Amps] HV Supplies and Diodes
> >
> >
> >>
> >> When a string of series-connected diodes is reverse-biased
> >> (during part of the cycle), the voltage drop across one is
> >> proportional to its leakage resistance. If the junction of the
> >> diode type has significant capacitance, then that enters into
> >> the picture too.
> >>
> >> If you use, in parallel with each diode, a resistor whose value
> >> is a fraction of the leakage resistance, then those resistors will
> >> swamp the leakage and so tend to equalize the voltage drop
> >> across each diode in a string.
> >>
> >> If you use, in parallel with each diode, a capacitor whose
> >> value is several times that of the junction, then those capacitors
> >> will swamp the junctions and again tend to equalize the voltage
> >> drop across each diode in a string.
> >>
> >> During the forward-conduction part of the cycle of course
> >> we have no problems with any of the above.
> >>
> >> I am not familiar with the rules on avalanche diodes.
> >>
> >> - Jim WB6BLD
> >>
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps@contesting.com
> >> http://lists.contesting.com/mailman/listinfo/amps
> >>
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
-----------------------------------------
Email sent from www.virginmedia.com/email
Virus-checked using McAfee(R) Software and scanned for spam
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|