So a couple of months ago I bought a Yamaha Rex 50 digital effects unit from the 1980’s.

I opened it up for cleaning, to check the electrolytic capacitors (some need replacement) and to swap out lithium coin cell battery that backs up the user’s saved settings.

Since the battery was working, I assumed it had been replaced.

Nope, the working lithium coin battery has a date of November 1987 which is very early so far as I understand.

So it’s still there because if it’s still working after thirty five years, it will probably be working for the two or three years I can expect from a new battery.

It was refreshing to experience an engineering design driven by long reliability in a piece of digital electronics.