I have an HP-80 that's working perfectly except for one strange behaviour: any attempt to calculate using the top 5 keys (e.g., present value) causes the display to go blank until the calculator is turned off and then on. The calculator accepts inputs for each key, it just won't calculate the answer when the key for the dependent variable is pressed.
My other HP-80 works just fine using the same inputs. Any idea what's happening?
Edited: 3 June 2010, 4:02 p.m.