[Boatanchors] #44/47 Bulb replacement with LEDs
Garey Barrell
k4oah at mindspring.com
Sat Feb 5 12:09:50 EST 2011
If you switch to #755s they'll last MUCH longer. Same voltage, current,
slightly less light, life = 20000 hours as opposed to 3000 hours for the 47.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Michael A. Bittner wrote:
> I didn't know there were AC/DC LEDs. However, I think I'll just stick
> with my small supply of #47 LERs (Light Emitting Resistors). W6MAB
>
> ----- Original Message -----
> *From:* Bob Jackson <mailto:bob at nofrowns.net>
> *To:* k4oah at mindspring.com <mailto:k4oah at mindspring.com> ;
> boatanchors at puck.nether.net <mailto:boatanchors at puck.nether.net>
> *Sent:* Saturday, February 05, 2011 8:25 AM
> *Subject:* Re: [Boatanchors] #44/47 Bulb replacement with LEDs
>
> All -
> The LEDs I've ordered are, indeed, AC/DC types and are supposed to
> draw about 20 mils. See
> http://cointaker.com/searchquick-submit.sc?keywords=g44f for an
> example.
> Bob AG5X
>
> ----- Original Message -----
> *From:* Garey Barrell <mailto:k4oah at mindspring.com>
> *To:* boatanchors at puck.nether.net
> <mailto:boatanchors at puck.nether.net>
> *Sent:* Saturday, February 05, 2011 10:03 AM
> *Subject:* Re: [Boatanchors] #44/47 Bulb replacement with LEDs
>
> Al -
>
> Apparently the filament will carry the full 150 mA through
> that tapped
> section, rather than the ~75 mA it sees with a parallel #47.
> I suppose
> the higher failure rate of this filament section in radios run
> with
> blown bulbs could be coincidental, but I've replaced a LOT of
> 34W4 and
> 35Z5 rectifiers in my life, and most of them had a blown bulb
> and Pin
> 4-6 (or 2-3) open.
>
> It makes sense that the entire filament would be able to
> handle 150 mA,
> but without a bulb that filament section is dissipating a
> little over 1W
> and with a bulb a little less than 1/2W, not counting the DC
> current
> which also goes through the filament. So without a bulb that
> section
> would be the most likely to fail. Of course these were both very
> inexpensive tubes, and a bulb or even a resistor cost money in
> a VERY
> price competitive market.! :-)
>
> As for the original question, if the LED was of the AC/DC
> types, it
> should work fine. The voltage across the tap is 7.5 V with NO
> parallel
> load and as long as the LED will handle that voltage it should
> be ok.
>
> 73, Garey - K4OAH
> Glen Allen, VA
>
> Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
> and TR-4/C Service Supplement CDs
> <www.k4oah.com <http://www.k4oah.com>>
>
>
> Al Parker wrote:
> > Hi folks,
> > In the AA5 or 35W4 application, aren't we missing one of
> the
> > purposes of the lamp? It provides a load to balance out the
> voltage
> > wanted across the tube filament. An LED lamp is much lower
> a load, in
> > the neighborhood of 10%, so it's not going to serve that
> purpose.
> > 73,
> >
> > Al, W8UT
> > www.boatanchors.org <http://www.boatanchors.org>
> > www.hammarlund.info <http://www.hammarlund.info>
> >
> > "There is nothing -- absolutely nothing -- half so much
> > worth doing as simply messing about in boats"
> > Ratty, to Mole
> >
> > On 2/5/2011 10:07 AM, Michael A. Bittner wrote:
> >> Chuck, Thanks for the info and data sheet on the 35W4.
> Looks like it's
> >> OK to use the 35W4 in a series string without harm as in my
> Knight Ocean
> >> Hopper and according to the alternate diagram on the data
> sheet.
> >> This still leaves us with the question of how one of these
> #47 bulb LED
> >> substitutes would work in an AA5 radio. After all, the D in
> LED stands
> >> for diode. W6MAB
> >>
> >> ----- Original Message -----
> >> *From:* Chuck <mailto:wcmoore at verizon.net>
> >> *To:* infomet at embarqmail.com
> <mailto:infomet at embarqmail.com> <mailto:infomet at embarqmail.com>
> >> *Cc:* boatanchors at puck.nether.net
> <mailto:boatanchors at puck.nether.net>
> >> <mailto:boatanchors at puck.nether.net>
> >> *Sent:* Friday, February 04, 2011 9:45 PM
> >> *Subject:* [Boatanchors] #44/47 Buld replacement with LEDs
> >>
> >> The 35W4 is a bit of a strange bird. The filament is
> tapped but
> >> rather than
> >> being tapped at the center like the venerable 12AU7 and
> similar
> >> valves the
> >> 35W4 is offset so that there are different drops across
> each
> >> filament section.
> >> From Pin 3-4 with a #47 Lamp the filament drop is 32
> Volts. From
> >> Pin 4 - 6
> >> the nominal drop is 5.5 volts.
> >> For more info see the datasheet at the follwoing URL:
> >> http://www.r-type.org/pdfs/35w4.pdf
> >> > Great question......thanks, Mike!
> >> > 73....Walter - K5EST - Missouri
> >> >
> >> >
> >> > On Thu, Feb 3, 2011 at 7:39 PM, Michael A. Bittner wrote:
> >> >> How would these work in an AA5 radio where the #47 bulb
> is often
> >> >> connected
> >> >> across one half of the rectifier heater? Rectifiers are
> >> typically 35Z5 or
> >> >> 35W4 with center-tapped heater. Mike W6MAB
> >> >
> >> > _______________________________________________
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> >> > Boatanchors at puck.nether.net
> <mailto:Boatanchors at puck.nether.net>
> >> > https://puck.nether.net/mailman/listinfo/boatanchors
> >> >
> >>
> >>
> >>
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