[time-nuts] Atomic Clocks: It is important that they keep good time, Part 1

[ed breya]

Yes Paul, LEDs wear out over time. By the late 70s and into the 80s, I 
think they were improved and perfected to the point where wearout is 
very slow and barely noticeable visually, and efficiency is much higher 
compared to the oldies. Even opto-couplers are sometimes specified for 
LED wearout, in the form of CTR degradation over time.

I don't know what vintage were used in these clocks, but they are fairly 
old, and likely have lots of running hours in this application. The ones 
in mine still look good, but I did look into replacements way back when 
I started - at least for spares in case any crapped out. I don't recall 
the part numbers or package style/pinout, but do recall they were 
HP-made. Putting more modern ones in would likely improve the display, 
and could reduce the power needed to light them - that is, if the 
pinouts and styles can be found that readily match up with the oldies. I 
think I probably have set aside some of the same types salvaged from 
other HP gear from that era, but if enough went bad or I wanted 
improvement, I'd look at newer stuff.

Ed