HP-41C memory module problem


I have an HP-41C which stopped working in 1984. Following advice from John Robinson in this forum I opened the calculator up yesterday, and using some circuit board cleaner managed to get it working! My next problem was the ports - only 1 and 3 worked. Once again, judicious use of the cleaner and a certain amount of jiggling and, hey presto, all four work now when application modules are plugged in. However,...

None of my memory modules work in any port. I have a quad memory module and three single memory modules and none of them work. As they have all been stored all these years in anti-static bags in the same box as the application modules I find it hard to believe that they are all faulty, although I guess it is possible. Their existence is simply not recognized by the calculator, even when I hard reset. I cannot SIZE more than 60-odd.

Has anybody out there got any ideas? How does the calculator know it has a RAM module plugged in instead of a ROM module? Is there anywhere else I should be applying the cleaner? (Rude answers will be filed for future reference.)


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