Panaplex display history

Jon Elson jonathanelson at
Sat May 30 13:29:57 CDT 2015

On 05/30/2015 12:40 PM, tony duell wrote:
>> LEDs themselves weren't all that much more costly than the typical pilot
>> lamp.  I recall sending $1 cash to Montsanto and receiving 2 red (was
>> there any other color?) LEDs in return in 1969.
> Is there a good reason why filament lamps were used on minicomputer
> front panels until the mid 1970s? Things like the PDP11/45, Philips P850, etc
> all used filament bulbs, not LEDs.
Inertia!  The 11/45 was designed before LEDs were available, and so they 
never changed.  To do it right, the PC board would have to be 
re-designed to add the current limiting resistor.  I did the mod on ours 
by adding the resistor to the LED lead, as the bulbs were pretty tall 
above the board.


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