11c hang-up


Hello everybody! That's the first time I write in this forum.

I have a problem with my HP 11c: From time to time it hangs up itself after pressing a key. That seems to appear more often after pressing a key in the upper row but I'm not sure about that.
Randomly the calculator then switches off (?, at least the display is off) or it's "freezing", that means the calc doesn't react at keystrokes but the display is showing nevertheless the last entry.
To awake the calc sometimes it helps just to press the "on"-key or "on" + "y^x" (several times in some cases), but in most cases I have to short-circuit the battery contacts. Then it restarts with the normal "Pr Error" display.

Can anybody give me some hints which causes the fault may have and how I maybe fix that? Thank you!


I don't know if it is related but I had a problem five years ago with my 11C keyboard. It responded randomly to keystrokes and was related to the soldering ageing and cracking. You could apparently prevent it by flexing the machine. Someone resoldered it for me and it has been fine since then.


If it's a soldering problem: Are there any critical "hot spots" on the HP 11c layout where rersoldering is most likely necessary, and how can I identify them?

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