| Hewlett Packard 5082-7002 LED Display | |
| Written by AnubisTTP on 2021-01-25 |
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The origins of the 5082-7002, made by Hewlett Packard, are shrouded in mystery. This LED display can be found in no price guides or parts lists of the era, and does not appear anywhere in HP's databooks. By external appearance the 5082-7002 appears to be a crude and early part, yet the date codes on the few surviving examples suggest it was released well after the Monsanto MAN-2. It certainly was not produced in commercial volumes, at least based on the scarcity of surviving examples, yet HP appears to have assigned it a part number in line with it's other commercial releases. Regardless of this displays mysterious history, the 5082-7002 is almost surely the first 5x7 LED matrix produced by Hewlett Packard. The core of the device is an array of comb-style gallium arsenide phosphide LED dies bonded to a ceramic wafer. Each die was hand-placed by an HP semiconductor tech in a tedious manual assembly process. This ceramic wafer has been mounted in a ludicrously oversized metal bathtub enclosure with fritted bead pins and a glass cavity lid. The 5082-7002's huge package size causes real problems for any designer attempting to use this display; the gap between characters is so large as to render text practically unreadable. It is unlikely this LED was ever used in any products, and few examples seem to have survived to the present day. That said, the 5082-7002 is a certainly a visually impressive LED to the modern collector, and is a unique example of the early display engineer's art.
Hewlett Packard 5082-7002, normal operation. This early LED part is constructed using the same type of LED dies as the 5082-7000.
Hewlett Packard 5082-7002 LED display, 5x magnification. Note the comb-shaped top electrodes on each die; HP settled on this pattern because it would mask only 25% of emitted light while still distributing current over the entire die cross section.
The 5082-7002's comically oversized package makes it impractical for multi-digit displays.
Prior to final testing and shipping, each display was set onto an aging board, which exercised all of the
diodes in the array for 100 hours. Each display had to maintain an acceptable level of brightness at the end of
the 100-hour period or it was rejected.
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