Panaplex display history

tony duell ard at
Sat May 30 10:14:22 CDT 2015

> 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 

The Compucorp 320 series (and I assume 340 series, etc) used the same size Panaplex display as the HP9815
(may even be the same part) although they were handheld-ish machines ( for those with big hands ;-)) A little
earlier than the HP9815, so this does not invalidate your suggestion that the HP9815 was the last calculator
to use one. To be pedantic, wasn't there are later version of the 9815 with 4K RAM on the CPU board
(and no RAM expansion board) -- the 9815S or some such. That would probably be later than the -A model.

When did the HP59304 HPIB display come out and when was it discontinued? It uses a 12 digit Panaplex display

> 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 In calcs, they were largely superseded by vacuum-flourescent displays 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.

I am surprised about the lifetime claim here. The VF display is a hot cathode device, which tends to imply a 
shorter life than a cold cathode part. VF displays were commonly used in consumer electronics (VCRs, etc)
in the 1980s and 1990s over here, and uneven segment illumination due to low emission from the filament 
was a common fault. Conversely, my HP9815 and HP59304 are, AFAIK, still using the original panaplex
display unit with no problems.


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