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HP-71B - Two keys responding erratically - Printable Version

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HP-71B - Two keys responding erratically - anetzer - 07-17-2014 11:34 AM


I have found an early 71B which has two keys on the lower left edge (ON and Shift-f) which respond peculiar: Pressing them rather determined often gets no response but pressing them rather lightly and shortly and gingerly works.

I do not really want to disassemble a keyboard assembly that is rather well preserved elsewhere. Does anybody know less invasive tricks? Is there a possibility to clean the keyboard, apply contact spray etc without cutting and remelting keyboard stakes and disassembling the keyboard proper?

Thank you!


RE: HP-71B - Two keys responding erratically - anetzer - 02-01-2015 05:21 PM


Half a year has passed, but sorrily without an answer. I guess these are not the only two HP calculator keys that have gone awry in the history of pocket computing...?

I would be very happy if one of you might at least point me to some general musings on keyboard restoration in general and possibly the 71B in specific?

Thank you all!


RE: HP-71B - Two keys responding erratically - Geoff Quickfall - 02-01-2015 06:09 PM

Try doing a Google search like "hp museum: keyboard repairs".

Looking through the postings this week alone, check out the following and follow the links from this week:



The fact that your original post was missed depends on the activity and the flavour of the day. I have seen a post disappear in one day to to a popular post receiving many replies. Don't take it to heart. Also, this board slacks off on the weekends, busier during the week.

Sounds like a contact problem. Could be as simple as oxidation in which case a conditioner introduced through the pin hole on the reverse side of the keyboard would help. It might be loose heat stakes at that corner which would respond to an application of a solder iron to flatten the stake out. Do this while pressing down on the keyboard PCA.

If you follow the above links you will see others imbedded in the threads, follow them also. Let us know how it works out.


RE: HP-71B - Two keys responding erratically - anetzer - 02-04-2015 08:25 PM

Thank you Geoff,

I did some searching before I posted but most of the threads scared me quite a bit. I want to escalate my approach as responsibly as possibly. So some suggestions like cutting heat stakes are far out off my list of options for quite some time to come.

Now I do seem to have a bundle of useful starting points... So, thanks again!