Panaplex display history
jonathanelson at email.wustl.edu
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.
More information about the cctech