Panaplex display history
hilpert at cs.ubc.ca
Fri May 29 20:53:09 CDT 2015
On 2015-May-29, at 3:54 PM, Jules Richardson wrote:
> JOOI, does anyone know when Panaplex 7-segment displays started going the way of the dodo, to be replaced with LED displays (and, on the back of that, what were the advantages of a Panaplex-type display over an LED one?)
Panaplex and other 7-seg gas discharge displays were used in calculators up to the mid-70s. Actually one of the last uses in a calculator might be the HP-9815 (1975/6):
They were mostly used in desktops for the sake of the larger digit size but there were some pocket/handheld calcs that used the smaller versoions. In calcs, they were largely superseded by vacuum-flourescent displays which were easier to drive, had a longer life, and could also be made with bright, large digits.
Heathkit used them in some items into perhaps the late 70s.
They were also extensively in arcade/pinball games, as I'm sure many will recall. I'm not sure how late they were being incorporated into new designs in that arena.
In their heyday (early/mid-70s) I'd say they could produce a larger, more uniform, better contrast, display than the then-early LEDs. Would have to look at specs and some calculations but they were probably more energy efficient than LEDs.
> I just saved a few boards from a dumpster with such displays on (they're actually Beckman ones, not Burroughs), but I was a little surprised to see IC dates into 1981; I thought by then things had moved over to LED.
Yes, to be accurate, Panaplex was a Burroughs trademark. There was the Panaplex I series which had a metal grid anode in front of the segments for the anode, and the more-prevalent Panaplex II which has a conductive coating on the glass for the anode.
The Burroughs and Beckman displays are different in design. Generically, I refer to them as 7-segment gas-discharge displays. There were some lesser-produced designs from Japanese manufacturers.
Generally, their failing seems to be the cathode poisoning common to all neon bulbs, and 'burning' of the thin conductive anode coating where applicable.
> I'm almost certain that they're from old gas pumps - maybe the displays are just more readable in bright sunlight than LED? (there's a sticker on one of the PSU boards with a 'shipping date' in 1999)
Funny, I was about to mention that use. I remember them in use on gas pumps up to somewhere around the late-80s or early-90s. One of my bike routes takes me on a dike behind an industrial area. Sometime around the mid-90s I remember there being a yard filled with scrapped pumps, a lot of them missing the display/keyboard cover, so all the displays mounted on the big controller boards could be seen. I wanted to rescue some of them but never got around to pursuing it. I was kind of dissuaded by the thought they had mostly seen a long and continuous service life and may now(then) be of questionable reliability.
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