HP Forum Archive 06

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Alcohol warning Message #1 Posted by Erik Wahlin on 5 July 2001, 6:18 p.m. I believe you need to be careful when using alcohol around sesitive electronic circuits. Alcohol, I believe as well as water is a polar molecule and could effectively make high impedence connections to various circuits. Make sure that you dry out the calculator (evaporate the cleaning liquids) before turning on the calc.

Re: Alcohol warning Message #2 Posted by Tony Duell on 5 July 2001, 7:03 p.m., in response to message #1 by Erik Wahlin Alcohol may be polar, but it sure isn't ionic, which is what really causes some liquids (including impure water) to conduct. I've just measured the resistance of some propan-2-ol. With about 1/4" depth in a container and a couple of probes about 1/4" apart, I was getting resistances of the order of 20M Ohms. So I think the resistance of the remaining film of alcohol after cleaning a calculator in it is not going to matter that much (most of the signals in an HP calculator come from considerably lower impedance sources than that). I'd not want to keep the batteries in while cleaning it, but if you take the batteries out, wash the calculator (or the boards, or whatever) in propan-2-ol, leave it for a few minutes to dry (it evapourates fast), it should be OK. Even if you leave the batteries in, I would be very suprised if it did any permanent damage. Incidentally, propan-2-ol is generally recomended for cleaning PCBs, precision mechanical parts, and so on. One warning, though. It doesn't attack much, but it can cloud up some optical plastics, which may have been used for lenses over LED displays. I'd not want to soak such a device with propan-2-ol. But apart from that, there's no problem that I've ever found. It is certainly a lot better than the contact cleaner/lubricants that are sold. And I don't even want to attempt to compare it to WD40 :-)....

Re: Alcohol warning Message #3 Posted by David Smith on 5 July 2001, 11:49 p.m., in response to message #1 by Erik Wahlin Isopropyl alcohol is a standard cleaning solvent used in the electronics industry for decades. There is no problem with it leaving conductive residue. It can cloud plastics particularly in its conventrated forms. I use cigarette lighter fluid to clean adhesive residue off of cases without any problems. It is also used with red jewlers rouge to polish scratches out of the red LED lenses. Always test a new solvent on an inconspicuous place when it doubt. Propanalol is a standard ingredient in most lens cleaning solutions and I have never had a problem with it attacking plastics. It is a rather gentle solvent.

Re: Alcohol warning Message #4 Posted by Luca - Switzerland on 6 July 2001, 3:35 a.m., in response to message #1 by Erik Wahlin It depends from the kind of alcohol. It seems that beer and gin tonic are not the right ones for electronic circuits, but you can test them on texas instruments calcs !

Re: Alcohol warning Message #5 Posted by Tony Duell on 6 July 2001, 2:04 p.m., in response to message #4 by Luca - Switzerland No, not gin or vodka :-). The stuff I use comes in a spray can labelled 'IPA' (Iso Propyl Alcohol, which is the old name for propan-2-ol), and claims to be 99.7% propan-2-ol. I've used it on a lot of electronic, mechanical and optical parts (I repair a lot more than just HP calculators :-)), and it's never done any damage. It does seem to be safe on at least some HP stuff too, for example it's what I use to clean the interboard contacts in HP41s.

Re: Alcohol warning Message #6 Posted by Miguel(Denver) on 7 July 2001, 12:37 p.m., in response to message #4 by Luca - Switzerland I can vouch for the baddness of beer in/on/saturating/electronics...I can also say that the next day, a little more level-headed, Isopropyl alcohol does wonders. For the device, NOT for your head!!!!

Re: Alcohol warning Message #7 Posted by Reinhard Hawel (Austria) on 8 July 2001, 4:19 p.m., in response to message #4 by Luca - Switzerland I prefer testing beer and gin tonic by drinking it. Unfortunately, normally there's no alcohol left after I found it suitable ... :-(

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