HP-41CX Issues!


I have recently been getting a problem where the calc starts displaying NULL or a program line while not being in program mode. Everything can be fine but if you tap on the calc it goes into this behavior. It seems to be in some program that it cannot get out of. Any thoughts as to why this might be happening?
Please let me know,


Your question does not give enough detail for me to understand exactly what is going on, but all 41 calculators will display NULL if a key is held down for more than a couple of seconds no matter what mode you have it in. If you are not holding the key down to long, it could be that the keys are getting weak or sticking.


I took the rubber feet off the bottom and one of the screws was loose by about a quarter turn. This seems to have resolved the issues. Now when I tap the sides of the calc, it does not go berserk. It is hard to believe that the calc is so sensitive to being tight like this. The calc is a Fullnut by the way.


The machine depends upon the four screws being properly tightened to hold all the pressure conatcts between the CPU and battery contacts to the keyboard. 95+ percent off all HP41 failures are related to contact problems (either dirt, corrosion, or broken screw posts/seats).

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