On Sat, 30 May 2015, Jon Elson wrote:
   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 
 
Hold on! Most 11/45 have LED frontpanels (such as mine from 1974). The
earlierst ones might have bulbs, but they switched to LEDs during
production.
Christian