Conductive Epoxy - Printable Version +- HP Forums (https://archived.hpcalc.org/museumforum) +-- Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum-1.html) +--- Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum-2.html) +--- Thread: Conductive Epoxy (/thread-173310.html) |
Conductive Epoxy - Kevin Kitts - 10-14-2010 I found a couple of old posts from 2000 on using conductive epoxy to repair old HP 41 calculator battery contacts. I have a 41cv from around 1981 that had a single (the leftmost) battery contact with corrosion and operation became intermittent and then finally failed. I applied some of the recommended conductive epoxy and now it seems to work perfectly. I am just wondering if either of the two original authors that discussed this are still around - and if the fixes they made in 2000 are still working after 10 years. In other words - what is the longevity of these kinds of repairs. Thanks All!
HP-41C battery contact fix I just discovered a relatively easy way of fixing the HP-41C series calculator battery contacts. These are the gold or other gold color metal plated contacts on the battery contact block. Battery corrosion and mechanical wear from the batteries tend to ruin these contacts. You can apply a conductive epoxy to the damaged areas and this seems to work. I don't know yet if this type of epoxy oxidizes in time which would cause it to fail later. The epoxy I used is made by Circuit Works (part # CW2400). It is available through Allied electronics and is not cheap at about $18 for the two tube set (7 grams). The tubes have Chemtronics (www.chemtronics.com) printed on them.(http://www.chemtronics.com/catalog/catalog.cgi?action=list_products&category=7) This product is normally used for circuit board trace repair. Please use at your own risk. Has anyone else out there ever used this type epoxy for battery contact repairs?
Re: HP-41C battery contact fix Hi Erik, Good idea! I've used the same stuff for several difficult to repair electrical contacts (e.g., attaching leads to solar cells and fixing rear window defroster contacts), but never for a contact that's likely to see some wear and tear. However, the stuff does seem to last for many years and does not break down easily, not even in outdoor applications. I'll bet that it holds up fine.
-Katie
Re: Conductive Epoxy - Katie Wasserman - 10-14-2010 It held up for a few years in my 41 but eventually failed because of the flexing -- I need to come up with a longer-term alternative. On rigid PCB's it seems to last forever and the repairs I've made years ago are all still good.
-Katie
Re: Conductive Epoxy - uhmgawa - 10-14-2010 Quote:
I've been concerned about this on legacy voyager units given
The primary point of failure is the seal of the LR44 cell in
Corrosion of the positive spring terminal seems less likely
Prevention is probably a far better route considering the Re: Conductive Epoxy - Katie Wasserman - 10-14-2010 LR44 cells are alkaline and I would not recommend them in a Voyager for the potential leakage problem you cite but more because of the much higher self discharge rate that they have compared to the 357 cells. 357 (also SR44SW) cells are silver oxide which have almost zero self discharge, almost never leak and if they do seem to have a less corrosive chemistry.
Re: Conductive Epoxy - uhmgawa - 10-14-2010 Quote:
I tend to have an abundance of LR44s on hand to feed digital
HP specifies voyagers for either LR or SR cell usage derating
I've had an SR44 eat a negative spring-style contact in an early
Edited: 15 Oct 2010, 1:29 a.m.
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