[Heath] Replacing dial lights with LEDS in SB-102

[Bill Cromwell]

Hi,

I understand the need for the current limiting (voltage dropping) series 
resistor. But I thought the 'D' in LED stands for um... diode. Why is 
another diode required? The LED should make it's own DC. I can't 
remember ever applying AC to an LED expecting it make it's own DC but 
the thought has occurred to me. Just that I don't know if I actually did 
it. Those are cheap so I will give it a try later tonight in my mad 
scientist lab. All I have to lose is an LED.

73,

Bill  KU8H

On 01/03/2017 11:54 AM, rgroh at swbell.net wrote:
> I don't have an exact answer to your question but I don't think there 
> is anything out there that gives you exactly what you want.  You are 
> entirely correct that most LED's are pretty much unidirectional - i.e. 
> they radiate in a front facing cone of light.  As an electronics 
> engineer (now retired) I rather rapidly slip into the design mode and 
> think about how I would make a solution. We need a structure to hold 
> an LED (or maybe 2 or three **) so they shine down into the dial area. 
> Then we need a small number of extra parts to drive the LED's (which 
> need DC) from the existing bulb source (essentially 12 VAC).  Then we 
> need a way to connect our new little LED assembly electrically to the 
> old bulb.  All very doable but they will require a bit of thought to 
> pull it off.  I don't own any Heathkit gear at the moment although I 
> certainly have some other older radios that could benefit from an LED 
> approach.
>
> Good luck - let us know what you find out.
>
> ** Two LED's might be a nice choice as you could put one across the 
> other in reverse polarity arrangement.  Then one acts as a reverse 
> protection diode for the other.  Also means a single dropping 
> resistor.  So 2 LED's and one resistor.
>
> 73
> Bob Groh, WA2CKY
>
>
> On Tuesday, January 3, 2017 8:40 AM, Joseph Smalley via Heath 
> <heath at puck.nether.net> wrote:
>
>
> I have posted this question once before about replacing the dial 
> lights with LEDS got a few suggestions.
>
> One was using LEDS from the Superbrightleds company.  They make a 
> great product.
>
> Unfortunately for me the LEDS I purchased do not project the light in 
> the right direction towards the plastic
>
> circular dial.  These LEDS shine the light straight out and in the 
> SB-102 that is down not at the circular dial.
>
> Has anyone used a different LED from this company that projects the 
> light at a 90 degree angle which would be
>
> pointing at the edge of the circular dial.  If so what color did you 
> use?  Was it Cool or Warm?
>
> I see a few on there website that may be what I need but I want to 
> make sure it could be used successfully
>
> because those I purchased are not what I needed.
>
> I did interact with there technical people but not sure if they 
> understood what I wanted to do.
>
> Any suggestions as I dont want to modify the SB-102 as I built it in 
> 1972 and want to keep it stock.
>
> 73 Joe WA3CKA
>
>
>
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