30 May
2015
30 May
'15
10:30 a.m.
On 05/30/2015 08:19 AM, tony duell wrote:
It would appear that in the early 1970s LEDs were very
expensive. I have been looking at the
HP5930x HPIB units and in many cases the status indicators (power on, listening, etc)
are
filament bulbs + driver transistors. I can think of no advantage to using a filament bulb
in this
application other than possibly cost. The 59304, which has a Panaplex display and
therefore
the HV supply to drive it, uses neon bulbs (NE2 sort of thing) as status indicators.
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.
By the mid 70s, LEDs in consumer applications were getting to be
ubiquitous. That microwave oven with the TMS1000 MCU (I'll look at the
date codes to get an exact date) had inch-high LED digits, driven by
discrete transistors.
--Chuck