HP Forum Archive 15

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Calc cleaning Message #1 Posted by Giancarlo on 11 May 2005, 4:23 p.m. I would like to make a thorough cleaning of my HPs (35 and 45). The general aspect of the calcs is "worn"; in particular, the keys and the front panel seem to be covered with a "patina" which prevents them from being shiny. In addition, one of them (15C) needs contacts cleaning. What should I use to get an efficient cleaning of the keys, front panel and back panel? (I'd rather know the name of the substances instead of their commercial brands - I might not be able to find them in Italy, where I live). Thanks for any input. Cheers. Giancarlo

Re: Calc cleaning Message #2 Posted by Mike H on 11 May 2005, 5:29 p.m., in response to message #1 by Giancarlo Hi Giancarlo, The best cleaning solvent would be a very dilute solution of hydroxide and hydronium ions as follows: 2 H2O <=> H3O+(aq) + OH-(aq) At room temperature, about 1 in every 10 000 000 molecules of this solvent has been dissociated by donating a hydrogen atom to another. Hydroxide ion is the caustic component of lye, and hydronium ion makes acid solutions corrosive. However, the concentrations in this solution are extremely low and not at all dangerous. Use caution however, because this solvent also reacts with atmospheric carbon dioxide which brings the pH of the solvent in an open-air container down to about 5.8. Good luck

Calc Cleaning Message #3 Posted by Bernhard on 11 May 2005, 5:32 p.m., in response to message #1 by Giancarlo For the Classics - complete disassembly. Keys alone soaked in 2-propanol 70% for a few hours and then scrubbed with soft electric toothbrush in the propanol bath. NEVER use any solvent such as 2-propanol or any other alcohol on any case part except the disassembled keys. The case shells are best cleaned only with a warm bath of mild detergent (soap) and a completely new (never used before) synthetic sponge. Do not scrub on the display area or protect it by adhesive tape before. If you scrub too hard the key legends will start to disappear, so be careful. Repairing keyboard contacts is another issue. The finest possible sandpaper will help if you can get at the contacts. Disassembly of HP15C (or any 20s series) keyboard is discouraged - you may destroy it. If you search the archives you can find more on the difficult topic of keyboard repair. I found that replacing the plastic membrane may help to get back the typical HP snap feeling. Anyhow, every HP that is preserved and brought back to functional condition is worth the effort.

Re: Calc cleaning Message #4 Posted by Frank Boehm on 11 May 2005, 6:09 p.m., in response to message #1 by Giancarlo I have received very good results with ordinary window cleaner and q-tips. Just wet the tip and start circling movement withou applying pressure. It might take you an hour, but the calculator will shine like new. But: try your cleaner on a spare calc, as there are many different mixtures; I would assume more expensive ones might be safer to use... For larger, rugged areas (not the keyboard area! - but the rest of the case), dishwashing detergent and a synthetic sponge work great, you should take care of any paper labels though (not foudn on HP calcs)

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