> How about the old trick of putting a power resistor in parallel with the
> zener to take some of the "heat."
>
> WA5JCI
>
> //I wouldn't do that; it makes for a pretty sloppy regulator, having no
> real "knee." I don't understand why hams resist simply using components
> designed for the task at hand -- am I missing something? I can buy DO-5
> case, 50W, 100Apk Iz rated, 5% tolerance zeners all day long for less than
> the cost of a six-pack of 807's. And just one will do the job, and likely
> outlast the operator.
>
> -WB2WIK/6
>
> Steve Katz wrote:
> >
> > I should add to my previous comment re DO-5 and outline drawings...
> >
> > A 5W "air cooled" diode usually isn't really air cooled. It's cooled by
> its
> > leads, in most cases; thus, the Rthj-a is not the formula used for
> > calculating junction temperature, but rather Rthj-L, where "L" is the
> lead.
> >
> > -WB2WIK/6
> >
> > "If everything seems under control, you're just not going fast enough."
> -
> > Mario Andretti
> >
> > > -----Original Message-----
> > > From: 2 [SMTP:2@vc.net]
> > > Sent: Thursday, July 18, 2002 2:07 PM
> > > To: Steve Katz; W8JI@contesting.com; AMPS; Douglas R Snowden
> > > Subject: RE: [Amps] Bias Zener Diodes In Parallel ?
> > >
> > > In the Digikey catalog, 5w zeners are axial-lead air-cooled devices.
> > >
> > > >
> > > >
> > > >
> > > >
> > > >> > [Steve Katz] Hi Rich. Case temp of a DO-5 stud,
> > > >>
> > > >> I have never seen anything smaller than 10w in a stud mount. 3A
> axial
> > > >> lead rectifiers are in a DO-5 case.
> > > >>
> > > > ??? Not sure what you mean, here. The DO-5 zener devices I use
> are
> > > >normally rated 50W at 55 degrees (C) Tc. Readily available from many
> > > >sources for a few dollars. The advantage is their high peak current
> > > rating,
> > > >usually hundreds of Amperes for a low-value Vz. 3A axial lead
> rectifiers
> > > >aren't DO-5, they're usually DO-2, DO-41, DO-42, etc.
> > > >
> > > > -Steve WB2WIK/6
> > > >
> > > >
> > > >
> > > >> - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> > > >> www.vcnet.com/measures.
> > > >> end
> > > >_______________________________________________
> > > >Amps mailing list
> > > >Amps@contesting.com
> > > >http://lists.contesting.com/mailman/listinfo/amps
> > > >
> > >
> > >
> > > - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> > > www.vcnet.com/measures.
> > > end
> > >
> > > _______________________________________________
> > > 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
|