Repairing my vintage Casio CA 901 calculator watch

Some time ago one of my colleagues at work showed up with a vintage calculator watch he just bought at an auction. This triggered me to check if my vintage Casio CA 901 from the early 1980’s would still work. The best thing about this watch was not only the calculator but it had a game included.

Unfortunately I did not remove the batteries some 30 years ago… Well, this caused some issues with contacts and some parts of the circuit board needed some touch up.

But at the end, after some intense checking of the circuits and some frustration along the way the watch is back to live and working nicely. Only issue is that you cannot set the calendar to a date beyond 1999. But who thought, that a watch like this would still be used in 2019…