HP Forum Archive 21

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HP-25 Message #1 Posted by aj04062 on 24 Mar 2012, 10:55 a.m. Is it safe to entirely submerge the main board of these units in a vinegar bath to remove corrosion? I would take the LED module off first. Thanks

Re: HP-25 Message #2 Posted by db (martinez, ca.) on 24 Mar 2012, 11:37 a.m., in response to message #1 by aj04062 i would dunk the whole thing for a few minutes, then rinse it with distilled water a few times and let it air dry for a couple of days. if you're worried about the led module and there's no green stuff up there then why not just leave it's head out of the vinegar?

Re: HP-25 Message #3 Posted by bill platt on 24 Mar 2012, 11:38 a.m., in response to message #2 by db (martinez, ca.) I had zero success trying to clean a 41. The green stuff just keeps coming back.

Re: HP-25 Message #4 Posted by db (martinez, ca.) on 24 Mar 2012, 2:32 p.m., in response to message #3 by bill platt bill; i wonder if using "no-ox" or something like it on a well cleaned area would keep the creping crud from coming back in your problem 41. if not at least it would be easy to clean off again. the big problem i see there would be that it's a dust attractant. has anyone tried to cover well cleaned traces with lacquer (not liquor)?

Re: HP-25 Message #5 Posted by Randy on 24 Mar 2012, 2:31 p.m., in response to message #1 by aj04062 Yes, but that might not be the best approach, especially if you don't know if it works. I have found that solder that has been exposed to battery electrolyte is bad enough, it's worse after additional oxidation from vinegar. So, my approach to Woodstock repair is to first remove all IC's and test them in a socketed board. If the unit warrants repair, I then treat the board corrosion with 100% DeOxit. Let it soak for several days then rub with cotton swabs to remove all the crud. Especially bad cases may need several treatments and some more elbow grease. Don't get vinegar anywhere near the LED array. The assembly is not sealed and one mil aluminum wire bonds don't survive the treatment.

Re: HP-25 Message #6 Posted by db (martinez, ca.) on 24 Mar 2012, 2:36 p.m., in response to message #5 by Randy Randy; we were posting at the same time. thanks for the real word on the subject. i'll have to pick up some of that deoxit. -db

Re: HP-25 Message #7 Posted by Randy on 24 Mar 2012, 2:51 p.m., in response to message #6 by db (martinez, ca.) When I first heard about Caig products (ProGold, DeOxit) I thought to myself... snake oil. It's just a marketing ploy - charging lots of money for an itty bitty bottle of the stuff. You know, a paltry 25 milliliters for thirty five bucks? You've got to be kidding. I've bought top shelf perfume for the wife for less... Yeah... I was wrong, again.

Re: HP-25 Message #8 Posted by aj04062 on 25 Mar 2012, 9:25 a.m., in response to message #5 by Randy Randy, Does the De-Oxit interfere with trying to re-solder the chips back in?

Re: HP-25 Message #9 Posted by Randy on 25 Mar 2012, 11:24 a.m., in response to message #8 by aj04062 Not at all. Just wipe it off and solder away.

Re: HP-25 Message #10 Posted by Kees Bouw on 25 Mar 2012, 3:10 p.m., in response to message #5 by Randy Quote: I then treat the board corrosion with 100% DeOxit. Let it soak for several days then rub with cotton swabs to remove all the crud. There are many Caig DeoxIT products available on http://store.caig.com. Can you please be more specific about which product to use for treating board corrosion? Thanks! Edited: 25 Mar 2012, 3:11 p.m.

Re: HP-25 Message #11 Posted by Randy on 26 Mar 2012, 6:48 a.m., in response to message #10 by Kees Bouw D100L-25C is what I use

Re: HP-25 Message #12 Posted by Luiz C. Vieira (Brazil) on 24 Mar 2012, 7:01 p.m., in response to message #1 by aj04062 HI. I succeeded cleaning many mboards with the greenish cooper oxide after using heated, diluted alcohol vinegar (50% with water, tepid). I never did it with LED modules neither with keyboards. The keyboards particularly because you cannot be sure all of the residual material leaves the surface of the contacts. After the 'thing' is dried I usually spray micro oil (many brands, many types; WD40 particularly leaves a protective coat that is not welcome in greasing circumstances) and spread as much as possible, till it becomes the thinest coat. Because the board is not supposed to be touched and manipulated so often, leaving it inside the calculator with the micro oil protective coat will significantly reduce the chances of future oxidation. Cheers. Luiz (Brazil)

Re: HP-25 Message #13 Posted by Eddie W. Shore on 26 Mar 2012, 9:26 a.m., in response to message #1 by aj04062 Quote: Is it safe to entirely submerge the main board of these units in a vinegar bath to remove corrosion? I would take the LED module off first. Thanks Slightly OT: It would be awesome to see the HP 25C calculator be released, but this time be solar powered.

Re: HP-25 Message #14 Posted by Russell Dobson on 30 Mar 2012, 3:23 a.m., in response to message #13 by Eddie W. Shore It must be badly corroded? I certainly wouldn't be that brave, but I'm no expert...

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