HP Forum Archive 15

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help with an HP 48s Message #1 Posted by e.young on 2 Mar 2006, 12:26 p.m. Greetings to all. I recently aquired an extremely used HP48s in a non-working condidition. Even though it doesn't work, I picked it up in hopes that I might be able to fix it. This thing had the batteries leak, so there is corrosion in the battery compartment. That I think I can deal with, but the entire unit is filthy, to the point that I don't like to touch it. I wonder if maybe it came out of a wet lab. Does anyone have any advise on how this might be cleaned? The amount of dirt is way more than just a cosmetic problem-this thing is nasty. Based on other threads that I have read, I am considering soaking it in distilled water for a while. Any comments or sugestions will be greatly appreciated. Thanks.

Re: help with an HP 48s Message #2 Posted by Jan on 2 Mar 2006, 2:08 p.m., in response to message #1 by e.young Hi, I would not soak it in destilled water either. The point is, since there was battery-leakage, some (salty) remains of this are probably still present in the battery compartment and the rest of the unit. When these salts dissolve in destilled water, the water can no longer be considered as of "distilled" quality and becomes conductive. Moisture is very difficult to get out from a closed compartment (such as a calc). So unless you open it soon after you treated it with water and dry it very thoroughly there is a serious risk of short circuiting parts of the units electronics, with unknown consequences. Furthermore, salt water enhances corrosion. Concluding I would say: don't touch it with lots of water but try a gentle cleaning procedure with a (slightly) wet cloth. Wash your hand after it as well, you don't know what the thing has been in contact with. regards Jan

Re: help with an HP 48s Message #3 Posted by bill platt on 2 Mar 2006, 3:51 p.m., in response to message #2 by Jan If the batteries are out, and you run distilled water through it in copious amounts, I see more good than harm. The distilled water will have a thermodynamic interest in taking on all that battery detritus into solution, and by running fresh distilled water trough it, you will get it all out. After doing an initial 5 rinses in a short time period, I'd let it soak for 24 hours, and rinse it again.

Re: help with an HP 48s Message #4 Posted by Randy on 2 Mar 2006, 5:01 p.m., in response to message #3 by bill platt Cleaning will not help... I don't like to be a wet blanket here but my recommendation would be "don't bother" - it's not repairable. 99.9% of the 48's I've seen with a battery leak that no longer turn on cannot be repaired due to keyboard damage. The two battery contact areas are open into the calculator, the negative terminal is open into in the case right above the ON button traces. The electrolyte gets into the keyboard circuit and opens the ON trace. End of calculator. Sorry. PS: Many times it kills the entire bottom row: ON 0 SPC + Some other points about other topic above: 1) It's safe to immerse/wash HP's so long as the batteries are out of them and you do not reinsert batteries for at least two days after a wet event. You can shake all the excess water out a 48 and dry in a warm place with no problems what so ever. It takes about 24 hours. Most all electronics that are soldered together get washed somewhere along the manufacturing process. No big deal. 2) Never soak an HP for an extended period of time, especially a Pioneer or 48. The keyboard conductors are printed carbon and they can be damaged and even dissolved given the right conditions. The darker plastics used on cases also have a nasty habit of developing splotchy white areas when left in contact with liquids too long. Edited: 2 Mar 2006, 5:14 p.m.

Re: help with an HP 48s Message #5 Posted by bill platt on 3 Mar 2006, 8:22 a.m., in response to message #4 by Randy Quote: Never soak an HP for an extended period of time, especially a Pioneer or 48. The keyboard conductors are printed carbon and they can be damaged and even dissolved given the right conditions. Good to know. Thanks!

Re: help with an HP 48s Message #6 Posted by Han on 2 Mar 2006, 6:52 p.m., in response to message #1 by e.young I would first test whether or not the caclulator does not turn on due to the battery corrosion. If you clean the contacts, and a fresh set of batteries do not turn the calculator on, there may be a few other reasons. In two used HP48Gs of mine (bought from eBay), the blue inductor (I think that's what it is; it's just above the postive battery terminal) broke at the point where its legs were bent; only one of the leg was broken. By broken, I mean it was rusted (? not sure, but it looked like rust) to the point of breaking! In the HP48S/SX calculators, the contact point of the keyboard circuitry with the PCB oftentimes would not make proper contact. So keypresses do not get registered (e.g. the ON key).

Re: help with an HP 48s Message #7 Posted by e.young on 3 Mar 2006, 8:36 a.m., in response to message #1 by e.young Thanks all for your replies. I bought it for very little money, so if things don't work out I haven't lost much. I'll let you know how it goes.

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