Need help: Restoring HP41C

I haven't worked on a large number of calculators, and I am not familiar with the insides of that one, but if I understand what you are facing: Use denatured alcohol or other greaseless electronic cleaner and a tooth brush to thoroughly clean all the copper or plated metal contact areas. Use Windex or other glass cleaner to clean the conductive strips and LCD contacts (if any), then carefully dry them with a soft paper towel. Leave them on the paper towel until you are ready to reinstall them. (I'm talking about minutes here... not days!) Use a soft pencil eraser to polish the copper or plated metal contact areas. Be sure to find one that does not leave a rubbery residue! Pen erasers work great. Inspect your parts mechanically to be sure that they fit together tightly, and that they have not become loose from stress or wear. Fix as needed. Use a dry soft paper towel to dust off and rub the copper or plated contact areas for a clean and shiny surface. Here comes the tricky part: wet the strips with a very small amount of Windex on both sides. You want to create a light film here. Not dripping wet! Then quickly reassemble the strip and parts that make contact to it before the film dries. This will create a weak "sticky" bond that will not loosen up easily. I've done this procedure at least a thousand times (no kidding!) and unless I did something wrong or the parts were beyond salvation, it always worked. Good luck! -Bryan