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Can I replace the HP 11c display with one from a 12c? If possible, is this hard to do? How does the case come apart? Thanks for any suggestions.

Hi, John;

I'm not going to straight answer your question, instead I'll tell you that the newer HP12C (flat, not the Platinum) units have an LCD that's not compatible with the ones found in the earlier Voyagers. There are earlier HP12C units with an LCD that's compatible with the HP11C, but these must be units almost as old as the HP11C itself. I saw at least four types of internal design, and two of them have different LCD assemblies.

I am not sure if one can identify the LCD by external inspection; IIRC someone posted some matrial about this, maybe the status indicators have a difference. Based on what I saw so far, there are two different 'pin arrangement', and the newer ones (single 3V battery) also have different display because they operate with different voltages.

To separate the upper and lower cases is another issue. Under each of the rubber feet there's a screw, Philips-type head. And keep in mind that there are two small springs contacting both display and keyboard bezels (aluminum) with the back plane (also in Aluminun) and form an ESD-aware protetion.

Getting to the LCD itself is another issue...

Cheers.

Luiz (Brazil)

... and the history goes one here:
To remove the PCB, you must cut off the melted plastic heads. After workng on display and cleaning the rubber pad and keys, put the pcb back, make a support for the calculator, cut some small pins and prepare a fast epoxi glue. Drop the glue over the plastic pins and put something heavy over the pcb (actually I use small pins over pcb, in order the heavy mass do not touch the pcb).
After 1~2 hours it is done.
Good luck!
Artur