I repaired a Casio fx-602p recently, by harvesting a chip from a broken one, one of the tqfp ASICs. Worth it because eBay price from Japan for a working one is $250. I'd like an fx-603p, but they are going for $350.

This is like the Casio version of HP-41- alphanumeric keystroke programmable with cassette interface.

No plastic heatstakes (unlike HP), but you're hosed if the flex cable to the LCD is broken.

One of the most impressive things recently is the guy who made replacement LCDs for the classic Radio Shack / Sharp pocket computers (they don't use flex cables). That a hobbyist can do this at reasonable price is a sign that we are living in amazing times.

https://www.tindie.com/products/halfbakedmaker/lcd-replaceme...