Picked up this HP-21 calculator at a yard sale. Plugged in and it doesn’t seem to work and the display is not refreshing quickly. Power adapter is putting out what I think is the correct voltage more or less. Batteries looked ok, but are probably bad. With the batteries out (something you’re not supposed to do) the calculator display is stable but pressing buttons does nothing. Removed two rubber feet and the screws underneath. Careful prying separated the halves. The board interconnectors are pretty neat. So this is a problem (corroded and lifted trace)
And this as well… More corrosion.
So I’ll have to see about removing all of the corrosion and rebuilding the broken traces. I hope I won’t have to desolder any of the ICs but some of the corrosion runs underneath. Fun!