[Boatanchors] #44/47 Bulb replacement with LEDs

[Michael A. Bittner]

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 
  To: k4oah at mindspring.com ; 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 
    To: 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>


    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
    > 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>
    >>     *Cc:* 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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    >> >
    >>
    >>
    >>
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