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):
http://www.cs.ubc.ca/~hilpert/eec/calcs/HP9815A.html
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calcs, they were largely superseded by vacuum-flourescent displays which were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.
