[Boatanchors] #44/47 Bulb replacement with LEDs

[Bob Jackson]

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
  >> >
  >> > _______________________________________________
  >> > Boatanchors mailing list
  >> > Boatanchors at puck.nether.net
  >> > https://puck.nether.net/mailman/listinfo/boatanchors
  >> >
  >>
  >>
  >>
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