PACKARD 4-DIE LEDs
Manufactured by Hewlett-Packard (www.hp.com)
Last updated 10-26-11
These are unique, vintage LEDs sent to me by J.J. in late-October 2011.
They differ from normal, 5mm (T1¾) through-hole LEDs in two significant ways.
1: They have a flat, lensless design and their transparent epoxy cases are tinted in the emitted color so you could tell them apart in your parts bin.
2: They have not one die, and not two -- but FOUR (4) dice to help boost their otherwise somewhat feeble light output.
The four dice appear to all be connected in series; hence these LEDs have a significantly higher Vf (forward voltage) than is usually found with single-die LEDs using the same operating chemistry.
You will note that these LEDs have three leads -- the center lead is there to allow you to operate the LED with only two dice; you will however require another ballast resistor otherwise you'll very likely fry them from excessive If (forward current).
These are the vintage HP 4-die LEDs, in red, amber, and yellow-green.
Spectrographic analysis of the red one.
Spectrographic analysis of the red one; spectrometer's response narrowed to a band between 630nm and 670nm to pinpoint peak wavelength, which is 642.10nm.
As you can see, this one broke already; one of the leads broke off so only two of the dice are illuminated.
This photograph shows the lead and a segment of epoxy encapsulant that snapped off; this is the first vintage LED to have ever become broken while in my custody. I normally "baby" vintage and antique LEDs, so it is uncertain why this one "went".
Spectrographic analysis of the amber one.
Spectrographic analysis of the amber one; spectrometer's response narrowed to a band between 565nm and 615nm to pinpoint peak wavelength, which is 584.980nm.
Spectrographic analysis of the yellow-green one.
Spectrographic analysis of the yellow-green one; spectrometer's response narrowed to a band between 540nm and 590nm to pinpoint peak wavelength (there are two peaks actually), which are 564.10nm and 568.92nm.
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