Old but still the best
Last year my Casio FX-850P "personal computer" started playing up. I've had this calculator for over 22 years and it's been a great unit, very easy to use with a good deal of handy features.
So I went out and spent some cash on a new TI-nSPIRE CAS graphing calculator. Well what a waste. Not only is it tedious to use and full of stuff I'll never ever use, it takes a minute to boot up! Way to long for wanting to do some quick calculations.
An hour with some jewellers screwdrivers, a new set of batteries and some air-in-a-can and the old FX-850P was back up and working. The TI-nSPIRE is now sitting in a drawer, never to see the light of day...