I have an HP41CX fullnut I repaired (changed bad memory chip, only 255 registers instead 319 registers) Now the repaired 41CX has 319 registers and 124 extended registers, the time clock works OK.
The problem is after not using the calculator for 1-2 days (without batteries), when I put batteries, the screen shows all characters @, "@@@@@@@@@@@@", twelve @ characters. After this, pressing the backspace keys, the calculator powers off. From this point, I can turn on the calculator (ON key, the screen shows 0.0000) but I cannot do a reset (ON + backspace), only after 1-2 minutes I can do a reset (ON + backspace) and the calculator works perfectly.
What is due the initial showing (twelve @ characters) when I put batteries after not using the calculator for 2 days and stored without batteries? I´m sure that is not due to a bad contact between the two halves of the calculator.