[R-390] Re: LED lamp replacement

[Cecil Acuff]

Put a big electrolytic in parallel with them...that should do it!

Cecil...
----- Original Message ----- 
From: "JamesMiller" <jmiller1706 at cfl.rr.com>
Cc: <R-390 at mailman.qth.net>
Sent: Wednesday, July 07, 2004 3:17 AM
Subject: Re: [R-390] Re: LED lamp replacement


> I prefer the "soft" on and off times of filament lamps over the
> instantaneous on-off of LEDs.  My filament dial lamps sort of "ramp up"
when
> they come on, which is the true behavior that should be observed in this
> genre of radi?  .  Ever drive behind a car with those obnoxious LED brake
> lights, especially the Cadillacs?, They flash on instantly... no soft warm
> up time.  It's grating on the nerves.
>
> ----- Original Message ----- 
> From: "John Kolb" <jlkolb at cts.com>
> To: "Tom Norris" <r390a at bellsouth.net>
> Cc: <R-390 at mailman.qth.net>
> Sent: Wednesday, July 07, 2004 1:26 AM
> Subject: Re: [R-390] Re: LED lamp replacement
>
>
> >
> > While there may be a possibility of RFI generated by the
> > LED's or (blasphemy) solid state diodes, I'm more curious
> > about the light output. The light out of LED's is rather
> > directional - how well do they work in the R-390?
> >
> > John
> >
> > On Tue, 6 Jul 2004, Tom Norris wrote:
> >
> > > I have not noticed any noise since replacing the bulbs with
> > > LEDs. I think I even put the scope to the line feeding them
> > > as this was mentioned before on another list a while back.
> > > My dial light replacements are fed with a series resistor
> > > followed by a diode, followed by two LEDs in series. There
> > > is a 1 mf cap in parallel with the pair of LEDs. There are
> > > now three junctions in the mix and the possibility of
> > > noise either by radiation or by propagation along
> > > the filament line. I may simply have overlooked any
> > > noise, I may not have actually been looking for it.
> > > I honestly don't remember, I've slept since then.
> > >
> > > Maybe a study is called for here, when I do the LED's
> > > on the current room-strewn receiver, I will make and
> > > record actual noise/ripple measurements.
> > >
> > > But before the RX gets done, I have to reassmble the
> > > Johnson Valiant, and before it gets done, I have to
> > > put a Transworld back together, so it may take a while.
> > >
> > > 73
> > >
> > > Tom
> > >
> > >
> > >
> > > >Instead of LED's, best bet is probably the long-life version of the
> standard
> > > >replacement bulb.  I think there's a reference on it and some list
> members
> > > >may know offhand what the number is.  As I recall, there is quite a
bit
> of
> > > >difference in the hours spec. and not that much difference in price.
> > > >Brightness may be a bit lower, though.
> > > >
> > > >Anyone know?
> > > >
> > > >Barry
> > > >
> > > >----- Original Message -----
> > > >
> > > >
> > > >>  Hi
> > > >>
> > > >>  If you do that then you have two items to worry about. The LED's
> have a
> > > >>  reverse breakdown voltage and you now have a half wave rectifier.
> That
> > > >>  gets you right back into the chopped current = RFI problem.
> > > >>
> > > >>  If you run them in reverse parallel pairs then the breakdown
voltage
> is
> > > >>  not an issue but you still only run current through them when the
> > > >>  voltage is above about 1.6 volts on the diode. Off of a 6.3 volt
AC
> > > >>  supply having no current for 1.6 volts is a fairly large amount of
> > > >>  chopping. You are right back to the RFI issue.
> > > >>
> > > >>  I know all this sounds a bit like witchcraft but the R-390 is
> > > >>  particularly vulnerable to the problem. The designers simply never
> > > >>  considered there would be a source of broad band RFI *inside* the
> > > >>  radio. The other gotcha is that it is such a sensitive radio that
> you
> > > >>  can hear crud with it that other radios would simply miss in the
> noise.
> > > >>
> > > >>  Take Care!
> > > >>
> > > >>  Bob Camp
> > > >  > KB8TQ
> > >
> > > _______________________________________________
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> > >
> >
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