Panaplex display history

Chuck Guzis cclist at
Sat May 30 12:30:34 CDT 2015

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.


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