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HP Forum Archive 09

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Cleaning HP-45 switch contacts
Message #1 Posted by Steve on 18 Sept 2002, 4:35 a.m.

I have been using my trusty HP-45 daily but I am having trouble with flakey contacts in the keyboard.

I disassembled the calculator and cleaned the switch contacts with an electronic non-lubricating cleaner, followed by a lubricating type. Unfortunately the contacts are impossible to get at, and this didn't seem to help much.

Does anyone have a method of cleaning these switches?

I did notice a little sticker inside saying that back in May of 1976, HP did this for me, but I think it needs it again!!

Thanks, Steve RPN'g since 1975

      
Re: Cleaning HP-45 switch contacts
Message #2 Posted by warren on 18 Sept 2002, 6:58 a.m.,
in response to message #1 by Steve

I have had success as follows: Cut some strips of virtually any kind of paper (I used a piece from a small notepad) approximately 3/16" wide by 3" long. Slide the paper under the raised key contact strip, between the strip and the keyboard below. Soak the paper with a contact cleaning fluid. Press down on the key contact strip, and pull the paper through. Repeat several times for each key. You may find advice to use extremely fine sandpaper instead of paper, but I have been told that that is not a good idea. Good luck.

            
Re: Cleaning HP-45 switch contacts
Message #3 Posted by Steve on 18 Sept 2002, 4:24 p.m.,
in response to message #2 by warren

Oh I get it, the idea is to burish each contact under the spring steel.

OK, I'll try that next. Thanks! Steve

            
Re: Cleaning HP-45 switch contacts
Message #4 Posted by David Smith on 18 Sept 2002, 5:52 p.m.,
in response to message #2 by warren

I use 1500 grit sandpaper with a drop of Caig Pro Gold contact cleaner on it. Insert strip (1/8 x 2 inches) under the offending key, press down on the key, and draw the strip through. Onc pass on each side of the contacts should be enough.

I have tested the 1500 grit paper on the gold plated etches and it takes quite a few strokes to start wearing the gold, and it does work much better than plain paper.

                  
Re: Cleaning HP-45 switch contacts
Message #5 Posted by Steve on 19 Sept 2002, 2:07 a.m.,
in response to message #4 by David Smith

David & Warren,

Thanks for the tips, yep it worked great! I used a fairly rigid paper and some Caig De-Oxit. While this cleaner didn't work as a passive spray, using the wiping action fixed it right up.

So if it works for another 27 years, that should be just fine.

Thanks again!

Steve


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