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Having acquired an used, but a fully functional HP11C I noticed a small piece of dirt behind the display glass (on its back side). I would like to remove it. Would it be a problem to reach this part here after opening the calculator. How to disassemble this part and to assemble it back?

Thks in advance.

1. Remove the 4 rubber feet,4 screws and back panel.
Attention please. You have 2 antistatic springs on the printed board
2. Use a vacuum cleaner carefully
3. Replace the back panel, 4 screws and 4 rubber feet.
Good luck!

Hello, Nenad;

Just check your 11C for the possibility it is an older model; this way, IF it is one of these, the PCB for the keyboard is different of the one used for the LCD + IC's (that are built in a flex circuit). These old calculators may have the LCD unit carefully removed, and they have eight small rubber foam to prevent from mechannical shock. Everything Emmanuel wrote is still a fact, and this other possibility may be taken into account.


Many thanks to you both, Luiz-Claudio and Emmanuel. This is really an old model, made in USA. It was pretty easy to lift the LCD unit up and to remove the dust. After opening the machine, I was impressed with every detail in it; how robust it is.

After assembling and tightening the screws, the baby works perfect.

Thanks again, dear friends, this Forum is just great.