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<DIV>Hi Bill</DIV>
<DIV> </DIV>
<DIV>You need to take into account the reverse breakdown voltage of the LED
when applying 12.6v AC to it which is why I suggested a series rectifier diode
to remove that issue.</DIV>
<DIV> </DIV>
<DIV><FONT lang=0 size=2 face=Arial FAMILY="SANSSERIF"
PTSIZE="10">73<BR></FONT><FONT lang=0 color=#0000ff size=4 face=Arial
FAMILY="SANSSERIF" PTSIZE="14"><I><BR>Bob</FONT><FONT lang=0 color=#000000
size=2 face=Arial FAMILY="SANSSERIF" PTSIZE="10"></I><BR>Bob F Burns G3OOU,
G-QRP 6907, @BobFBurns<BR>Crystal Palace Radio & Electronics Club: <A
href="http://www.g3oou.co.uk/">www.g3oou.co.uk</A><BR>Technical web site: <A
href="http://www.qsl.net/g3oou">www.qsl.net/g3oou
<DIV> </DIV>
<DIV>
<DIV>In a message dated 03/01/2017 20:35:44 GMT Standard Time,
wrcromwell@gmail.com writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" color=#000000 size=2
face=Arial>Hi,<BR><BR>I understand the need for the current limiting (voltage
dropping) series <BR>resistor. But I thought the 'D' in LED stands for um...
diode. Why is <BR>another diode required? The LED should make it's own DC. I
can't <BR>remember ever applying AC to an LED expecting it make it's own DC
but <BR>the thought has occurred to me. Just that I don't know if I actually
did <BR>it. Those are cheap so I will give it a try later tonight in my mad
<BR>scientist lab. All I have to lose is an LED.<BR><BR>73,<BR><BR>Bill
KU8H<BR><BR>On 01/03/2017 11:54 AM, rgroh@swbell.net wrote:<BR>> I don't
have an exact answer to your question but I don't think there <BR>> is
anything out there that gives you exactly what you want. You are
<BR>> entirely correct that most LED's are pretty much unidirectional -
i.e. <BR>> they radiate in a front facing cone of light. As an
electronics <BR>> engineer (now retired) I rather rapidly slip into the
design mode and <BR>> think about how I would make a solution. We need a
structure to hold <BR>> an LED (or maybe 2 or three **) so they shine down
into the dial area. <BR>> Then we need a small number of extra parts to
drive the LED's (which <BR>> need DC) from the existing bulb source
(essentially 12 VAC). Then we <BR>> need a way to connect our new
little LED assembly electrically to the <BR>> old bulb. All very
doable but they will require a bit of thought to <BR>> pull it off. I
don't own any Heathkit gear at the moment although I <BR>> certainly have
some other older radios that could benefit from an LED <BR>>
approach.<BR>><BR>> Good luck - let us know what you find
out.<BR>><BR>> ** Two LED's might be a nice choice as you could put one
across the <BR>> other in reverse polarity arrangement. Then one acts
as a reverse <BR>> protection diode for the other. Also means a
single dropping <BR>> resistor. So 2 LED's and one
resistor.<BR>><BR>> 73<BR>> Bob Groh, WA2CKY<BR>><BR>><BR>>
On Tuesday, January 3, 2017 8:40 AM, Joseph Smalley via Heath <BR>>
<heath@puck.nether.net> wrote:<BR>><BR>><BR>> I have posted
this question once before about replacing the dial <BR>> lights with LEDS
got a few suggestions.<BR>><BR>> One was using LEDS from the
Superbrightleds company. They make a <BR>> great
product.<BR>><BR>> Unfortunately for me the LEDS I purchased do not
project the light in <BR>> the right direction towards the
plastic<BR>><BR>> circular dial. These LEDS shine the light
straight out and in the <BR>> SB-102 that is down not at the circular
dial.<BR>><BR>> Has anyone used a different LED from this company that
projects the <BR>> light at a 90 degree angle which would
be<BR>><BR>> pointing at the edge of the circular dial. If so what
color did you <BR>> use? Was it Cool or Warm?<BR>><BR>> I see a
few on there website that may be what I need but I want to <BR>> make sure
it could be used successfully<BR>><BR>> because those I purchased are
not what I needed.<BR>><BR>> I did interact with there technical people
but not sure if they <BR>> understood what I wanted to do.<BR>><BR>>
Any suggestions as I dont want to modify the SB-102 as I built it in <BR>>
1972 and want to keep it stock.<BR>><BR>> 73 Joe
WA3CKA<BR>><BR>><BR>><BR>>
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_______________________________________________<BR>> Heath mailing
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https://puck.nether.net/mailman/listinfo/heath<BR><BR>-- <BR>bark less - wag
more<BR><BR>_______________________________________________<BR>Heath mailing
list<BR>Heath@puck.nether.net<BR>https://puck.nether.net/mailman/listinfo/heath<BR></FONT></BLOCKQUOTE></DIV></A></FONT></DIV></FONT></BODY></HTML>