HP Forum Archive 14

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HP-34C repair Message #1 Posted by Fred G on 17 Nov 2004, 10:15 p.m. My HP-34C (the solderless type) has green corrosion leading from the battery terminals along the traces on the ribbon that connects to the interior. First, what is the best way to remove the corrosion? Second, if the trace has become interrupted, what is the best way to restore the continuity, should I use conductive paint?

Re: HP-34C repair Message #2 Posted by Vieira, Luiz C. (Brazil) on 18 Nov 2004, 1:27 a.m., in response to message #1 by Fred G Hi; I had two spices with corrosion in the battery connectors and the flex circuit (ribbon) that lead to corrode part of the power supply copper trails. Both units had soldered IC's and I mannaged to replace the ribbon for a piece of flat cable of the type used in computers. In your case, being your HP34C a solderless-type Spice, I'd mannage to remove the corroded trails off the ribbon and clean (using chemicals) all of the oxidation left in the copper trails. Then I'd rebuild the removed trails with new, self adherent copper strips (there is a company that sales self adherent cooper foil you can "cut and past"; I don't remember the name) by using the remaining non-conductive part of the flex circuit. I know it is a little bit vage, but when I face new situations I try to apply new solutions, if the known ones cannot fix the problem. I have in my mind what to do, and I have made some interesting repairs in "troubled" calculators. I wish I could help more. Hope you succeed. Luiz (Brazil)

Re: HP-34C repair Message #3 Posted by Fred G on 18 Nov 2004, 8:57 a.m., in response to message #2 by Vieira, Luiz C. (Brazil) Thanks for the tip. What chemicals will remove the oxidation? Also, let me know the name of the company that sells the conductive foil if you think of it.

Re: HP-34C repair Message #4 Posted by Vieira, Luiz C. (Brazil) on 18 Nov 2004, 12:12 p.m., in response to message #3 by Fred G Hi, Fred; about the chemicals for cleaning the corrosive material. I use (it would be a good idea to use other sources of information) weak acid, like vinegar with warm water. I use a particular type of vinegar that is based on alcohol instead of grape juice (it is transparent and leaves no purple spots). I mannaged to remember the name of the company that sells (thanks for reminding me...) the conductive foil: it is Chomerics and the one that told me about it i Renato, another brazilian contributor. (still) Hope you succeed. Let us know. Cheers. Luiz (Brazil)

Re: HP-34C repair Message #5 Posted by Jon on 18 Nov 2004, 1:38 p.m., in response to message #4 by Vieira, Luiz C. (Brazil) Hi: I have repaired a lot of spices with that problem. In my opinion the best option is rewiring. You should locate the three connection points in the AC/DC circuit and use silicone wires to restore the connection. It works excellent. I have some photographs of the work if you are interested. Regards Jon

Re: HP-34C repair Message #6 Posted by Vieira, Luiz C. (Brazil) on 18 Nov 2004, 10:02 p.m., in response to message #5 by Jon Hi, Jon; thank you for your support. I actually rewired two Spices already with the flat cable used in computers (that's the raw material I had in hands...) but the units where both of the soldered type. So, I removed the partially destroyed ribbon and rewired the whole thing. It worked fine, an dI also have at least one picture (I just need to find it). You mentioned silcon wires. I'd like very much to see the final aspect. Do you already have the pictures or you'd need to open the calculator to take them? I've once tried to solder patches over flex circuit, but I did not succeed doing a clean job. I tried using a 220Vac soldering iron connected to the 127Vac oulet, and this gave better results (by simply not melting the flex base...). Thanks a lot. Luiz (Brazil)

Re: HP-34C repair Message #7 Posted by Jon on 19 Nov 2004, 12:56 p.m., in response to message #6 by Vieira, Luiz C. (Brazil) Fred: I have sent an e-mail. Luiz: I donīt have your e-mail address.

Sorry! Message #8 Posted by Vieira, Luiz C. (Brazil) on 19 Nov 2004, 2:54 p.m., in response to message #7 by Jon Hi, Jon; I'm sorry not posting my e-mail address, I thought you'd post a link to the images. Please, my e-mail address is as follows: lcvieira at quantica dot com dot br (just to avoid autoSPAM... at least not the inteligent ones) Thank you very much. Luiz (Brazil)

Re: HP-34C repair Message #9 Posted by Fred G on 19 Nov 2004, 12:18 a.m., in response to message #5 by Jon Hi Jon, I would like to see the photos showing how you did the repair and I would like to get any information on where you obtained the repair materials and the methods. Fred

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