Amazing Luck!!



#2

I was browsing through a loca thrift store today, digging in their "Small Appliances" section, hoping to find an interesting old calculator or radio, and then, under a cracked old clock radio, I saw the HP logo. I moved the radio, a toaster and a tangled mess of old cords, and there it was. A boxed HP-41C. It had all the manuals with it. I bought it for $2. Now that I have it at home, I have looked through all the stuff that was with it. I have the HP-41C, in excellent shape, except for some heavy corrosion on the battery terminals, the original "N" cell holder, also corroded, fortunately, there were no batteries in it when I got it. A quad memory module, a Memory Module, the manuals and the brown (leather?) zipper pouch, and a little vynil holder for the modules and overlays. All in all, I think it looks pretty complete, I am off to the store to buy some "N" cells for it, and I intend to clean up the corrosion before testing it. What is the best method for removing such corrosion? Thanks!

Ian Primus
ian_primus@yahoo.com


#3

Hi;

I have been in this situation. What I did was focussing the cause: alkaline material. What`s the best neutralizer? Acid.

I used lemon juice diluted in warm/hot water (~ 70% water). I brushed the acid solution over the alkaline material with an old toothbrush. The corrosion is diluted fast.

Of course, you have to disassemble the calc (do you know how to do it?) and take the batt/IO assy out. You must be aware of the small foam that is built under the zebra contacts. Avoid moistening it. It must be carefully dried out before being placed back in the calculator.

I believe other, better ideas will come in. I have used this procedure many times. Oh, yes, a little coat of micro-oil (WD40 or similar) over the contacts will help avoiding corrosion. Yes, I know the oil is an insulating material, but a thin coat will not avoid contact between the batt/IO assy and the batteries or the keyboard/LCD assy.

Success.


#4

Well, I cleaned the corrosion up, and I got it all off, but I am going to need to do some serious work on the battery contact/module connector part. The batteries must have really exploded, there was blue gunk caked thick on the contacts, I was able to chip off the stuff on the middle two contacts, but the outer two, the ones that actually carry voltage, are almost completely eaten away - the battery acid ate right through the plastic conductor thing. Not only that, but the part of the connector that connects to the back of the keyboard is eaten really badly too. I was able to clean the actual PCB on the back of the keyboard, but the thin plastic conductor was eaten through in a couple places. Anyone ever repaired one of these before? Is there a place I can buy a new part? Thanks!

Ian Primus
ian_primus@yahoo.com

#5

> I believe other, better ideas will come in. I have used this procedure many times. Oh, yes, a little coat of micro-oil (WD40 or similar) over the contacts will help avoiding corrosion. Yes, I know the oil is an insulating material, but a thin coat will not avoid contact between the batt/IO assy and the batteries or the keyboard/LCD assy.

Isn't the contacts gold plated? Gold does not corrode, so I doubt that applying oil will do any good. Just keep leaking batteries out of it.


#6

Hi, Håkan;

this is very well noted, but corrosion is sort of a ghost in the 41`s batt/IO assy. The leakage can happen anytime, even for a "new", fresh batteries` set. The leaking is transparent at first appearing, but it reacts with oxygen and the battery's metal itself. The gold does not suffer any pain, but the cooper under it is corroded by the alkaline leakage that, somehow, increases the reaction (is it correct? I`m not a chemist). With oxygen, things get worst.

I have been using the micro-oils to avoid, at least, the contact with oxygen. I was lucky enough using batteries that leak after some months and the contacts prevail.

I can tell you the contacts` life increased somewhat with the micro-oil coat. I still believe better solutions exist...

Thanks. And best regards.

#7

I have found a product that works very well at cleaning and inhibiting future corrosion. It a called the "Gold Pen" from Caig corporation (www.caig.com). It is sold at electronics repair suppliers (and I think directly from them). It is like a felt tip pin that contains a (slightly oily) substance that fights corrosion. First clean up as much of the gunk as possible (I use 91% isopropyl alcohol) then apply the Caig pen as directed in their instructions.

It is important to remove all traces of corrosion (even microscopic ones) because remanants can act as "seeds" from which future corrosion can start growing.


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