The Museum of HP Calculators

HP Forum Archive 15

[ Return to Index | Top of Index ]

Cleaning an Hp41C
Message #1 Posted by Xavier LaRue on 16 Mar 2006, 4:46 p.m.

Hi there,

I recently buyed a hp41c + Quad mem and X function, but I don't know what hapened but when I received it is has like 1 inch of dust and other thing on it.. I clean it with rubbering alcool + q-tips but under the protective screen there still a lots of dust.. so my question is , how to open it.. also I have one key that don't click anymore and is a little bit harder to get entered correcly, so, do opening the calc will enable me to help this problem too,

So do somone have picture of how to open a FullNut starting with 20 and tips on how to clean the calc...

Thank you all, Xavier LaRue

Re: Cleaning an Hp41C
Message #2 Posted by Andreas Terzis on 16 Mar 2006, 7:32 p.m.,
in response to message #1 by Xavier LaRue


I have had the same problems in the last couple of months with machines I bought from 'crooks' on eBay (sorry friends - it's the most polite word I can use). In fact I recently bought a 'MINT' HP-41CX only to find it had tons of scratches on the sides, matte (non-shiny) keys probably from overcleaning, and the 'clean without corrosion' battery contacts to be FULL of corrosion!!!

In any event, I have read posts from before where people used 409 cleaner on the keyboard. You can open the machine by taking the four pads on the bottom off and unscrewing the four screws. There are some posts lately to me, suggesting to be very careful with HP-41C and HP-41CV machines, where HP-41CX machines are easier. The colleagues were suggesting to be careful with the former ones as the boards internally need some pressure to stay together. In fact, later machines that were Halfnuts (even HP-41CVs) would not be difficult to open. (Halfnuts are the ones with the rounded edges on the display - you probably don't have one of those).

Once you open the machine you can use distilled water and a Q-tip to clean the circuit boards inside. I would use some 'Dust Off' myself as well. That is the can that has some kind of condensed chemicals (difluoroethane). As far as cleaning the battery contacts, there was some discussion recently that one could use lemon juice or vinegar, and coat them with butter from what I understand. I just used lemon juice and a Q-tip and it cleaned most of the base deposits on the battery contacts of my machines (about 90%). I think the relevant post was called: 'Battery leakage and cleaning' but for some reason I cannot seem to access it, maybe due to the passworded changes to the site that were implemented lately by Dave Hicks; he can comment if that's the case.

I hope that helps a little bit. Good luck, Andreas

Re: Cleaning an Hp41C
Message #3 Posted by Klaus on 17 Mar 2006, 3:01 a.m.,
in response to message #2 by Andreas Terzis

I think it was me who said something about butter. DO NOT DO THIS! You can do this on a car's battery, but I would not do it on a 41C.

Also do not scrape the battery contacts, they are just thin foil!

Btw, repairing broken keys is not as easy as on the classic model

Edited: 17 Mar 2006, 3:53 a.m.

Re: Cleaning an Hp41C
Message #4 Posted by Xavier LaRue on 17 Mar 2006, 7:09 a.m.,
in response to message #3 by Klaus

So the point it,

Until it's completly broken.. don't fix it ?

Xavier LaRue

Re: Cleaning an Hp41C
Message #5 Posted by Klaus on 17 Mar 2006, 11:12 a.m.,
in response to message #4 by Xavier LaRue

Key malfunction due to dirt => fixable

malfunction due to broken domes (the key is lower than other keys) => bad luck

The reason: You do not have access to the keyboard contacts. The whole keyboard assembly is fixed with heat-stakes to the front plate of the case. Maybe professionals can fix broken keys (

Re: Cleaning an Hp41C
Message #6 Posted by jbssm on 18 Mar 2006, 9:55 a.m.,
in response to message #1 by Xavier LaRue


I also have had some problems with the 41C Series ... my advice is, try to get some pictures of the calcs you are buying on eBay, you can immediately tell the condition of a unit pretty surely by how it looks on a good picture ... and don't forget to ask a picture of the battery contacts.

Anyway, also on the spirit of this topic, does anyone have a good method to access the keyboard on the 41C series? Like a member said the circuits are pinned to the front plate by heat stakes, so does anyone found a good method of removing then and the put all back?

Regards, jbssm

[ Return to Index | Top of Index ]

Go back to the main exhibit hall