Where can I get 12V Grain-0-wheat lamps?

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MikeMl

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I need some 12V Grain of Wheat lamps for replacement in a radio I am rebuilding. I think that model train buffs use these.

Cheap Source?
 
Why not wire in a little LED and dropping resistor? Save you from having to replace the incandescent when it burns out.
 
I have heard that some modle train enthusisasts don't like the leds, they stick with the mini lamps for some reason.
 
duffy said:
Why not wire in a little LED and dropping resistor? Save you from having to replace the incandescent when it burns out.
Click to expand...
Because it could be an essential part of the circuit.

Grain of wheat lamps are often used as PTC resistors in things like wien bridge oscillators; if you replace it with an LED it might not work.
 
For a resistive-tuned local oscillator? Saw one in a frequency generator, I suppose it would make sense for a radio, too.
 
Hero999 said:
Grain of wheat lamps are often used as PTC resistors in things like wien bridge oscillators; if you replace it with an LED it might not work.
Click to expand...


I believe that it was David Packard who first described this application for his Master theses.
And the HP200B Audio Oscillator actually used this concept for stabilization.
 
Also, you can't solder to the leads, and the bulbs aren't the same size as the "grain of wheat".
 
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A light bulb shines all around in a sphere.
An LED shines in a fairly narrow angle in only one direction.

It might take 18 LEDs to shine in a sphere. Ten in a circle (36.5 degrees angle), four shining up and four shining down.
 
duffy said:
You can get LED's with 160° angles and even wider.
Click to expand...
Luxeon have very expensive and very powerful wide-angle LEDs.
The little LEDs in my solar garden lights have an angle of about 140 degrees.
I have never seen little ones sold except cheap Chinese ones on E-Bay.
 
I didn't know that Osram makes butter on a plate that glows in the dark.
The tiny LED is as bright as ordinary LEDs.
It has a nice wide viewing angle.
 
The bulk of 'ordinary' LED's is the packaging. The leads themselves are like 10 times or more the size of the actual P/N junction. If you send a REALLY tiny amount of current through a white LED and look down into the top of dome you can even see the fly wire that comes off one of the junctions. And the viewing angle is better cause they don't put the P/N junction in that little cup like that do on typical 5mm LED's.
 
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