Calculator Idiosyncrasies


I finally received my HP-80 and everything seems to be working fine, but I noticed some little idiosyncrasies with operations. I noticed the first one when I turned it on. In order to have the calculator turn on, I have to not only slide the on/off switch, but press and wiggle it a little bit when it is in the on position or the calculator will turn itself off. After I do this little maneuver it stays on and works fine - it's just a little diconcerting because I wonder if this will give me problems later?? The other idioysncrasy is with the zero key. I have to apply a significant bit of pressure to have it register and this sometimes causes multiple entries. I realize that this is part of the fun of owning a "Classic," but when does the concern rise to the level of attempting a fix. I'm sure others have similar experiences...? BTW - I love the LED's! They predate the time when I started using calculators, so this is new for me and I'm a convert.



The problem of the on/off switch is caused by the old grease. You should open the calculator, clean it and apply new silicone grease.
The 0 key will work perfect again if you clean the metallic part under it with isopropilic alcohol. Use a small piece of cloth impregnated with alcohol. Place it under the metallic part, press it and move the cloth until it is clean. I have done it hundreds of times with excellent result.


Opening it makes me a little nervous as I don't see how that can be done. Is there a simple way to get the HP-80 open without causing any damage? I would prefer to live with these issues instead of potentially damaging the calculator case.


By all means, open the machine up. The problems you describe are common and easy to fix. Perhaps this old post may be of use.


Thanks for the link. Obviously, the screws in the battery compartment are easy to get to in order to remove. However, it's not clear to me on how to remove the feet in order to get to those screws. Is there a method for removing them?


You don't have to remove the feet, just pry up one side (the outside edge) to get at the screws. You do realize that there are also screws underneath the label (at the upper left and upper right corners, about 1 cm in from the edges) right?


I do realize that these screws are hidden under the label. And from what I gather, these are trickiest to deal with if one wants to preserve the label. I've heard some suggestions on how to do it, but I would be curious to hear success stories and the methodology used.


Here's one method. I have also heard or read of using a solvent of some kind and a fine wire or thread to sort of "saw" the label off. If you search the Forum Archives, you might find some old posts that discuss this topic.

I have no personal success stories regarding either of the above, but I have never figured I had the ability or patience to try either. I personally don't think it looks all that bad to just cut a clean hole in the label, using a sharp knife and the edges of the hole as a guide. That will sure make future repairs easier.


I never try to totally remove the label. I just peel back the upper corners to expose the two screws. If you are careful and do not bend the label back sharpley, it can be hardly noticeable that it was repaired. I always leave the screws out so that future work does not risk more damage to the label.

To peel back the corners, I place a drop of UnDu (the solvent heptane) on the corner, a carefully work a razor blade dipped in more UnDu under the corner. The UnDu causes any adhesive to temporarily forget how to stick.

Usually the corners will stick back down just fine. Sometimes you have to reglue them. To do this I clean off all the old adhesive with alcohol. Then I use some Elmers contact cement. You brush the cement on the label corner and case. Don't let it pool in the label-case seam. Let the cement dry, the press down the label and rub with a soft cloth. The cement is neoprene rubber based and any excess rubs off.


If you do not feel comfortable opening up the calculator for the repair, or simply do not feel like goofing around with it, I highly suggest sending the calculator to Randy at and let him give it a full service.

He serviced my HP67 and did a great job with it.

Forum Jump: