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Woodstock Keyboard Designs - aj04062 - 01-19-2015 03:30 AM
Does anyone know when in 76 HP switched from metal strip keyboard contacts to plastic membrane?
I think it was in 76 sometime. Just curious as it seems like a very high rate of membrane styles I come across FAIL.
membrane style
![[Image: Keyboard2.jpg]](https://lh5.googleusercontent.com/-KXdYV-09cJM/VLx6pz0BQPI/AAAAAAAAJCI/mGVD8F9sdS4/s640/Keyboard2.jpg)
metal strip style
![[Image: Keyboard3.jpg]](https://lh4.googleusercontent.com/-3Ui2ig6n3Ag/VLx6rO6r82I/AAAAAAAAJCQ/DO5obykEFXk/s640/Keyboard3.jpg)
RE: Woodstock Keyboard Designs - PANAMATIK - 01-22-2015 03:47 PM
(01-19-2015 03:30 AM)aj04062 Wrote: Does anyone know when in 76 HP switched from metal strip keyboard contacts to plastic membrane?
I cannot answer your question. But I have some other keyboards with different dates printed on it. Perhaps this can give you some information. Others don't show any date.
And I know that the keyboard rows and columns were routed differently on the main board to the ACT processor pins in HP-21 and HP-25, so they behave different, HP-22/HP-25C has the same layout as HP-25. The membrane style keyboard in the third picture I found in two of my HP-29Cs.
I have even more (different date) keyboards, but couldn't add all images as attachment.
[attachment=1468][attachment=1469][attachment=1465][attachment=1466][attachment=1467]
Bernhard
RE: Woodstock Keyboard Designs - aj04062 - 01-22-2015 05:03 PM
That's interesting. I wouldn't have thought they had different routings between models!
RE: Woodstock Keyboard Designs - aj04062 - 01-24-2015 07:27 PM
I just replaced a faulty 29C board with one from a 21. Seems to work fine.
RE: Woodstock Keyboard Designs - Frido Bohn - 01-28-2015 01:42 PM
Just happened to my HP-25 that key "5" didn't respond anymore. I disassembled it and was confronted with the fact that you cannot remove the keyboard from the contact layer without destroying the plastic posts. I was lucky to find a metal-strip contact layer so I could just insert a tiny wire in the hole underneath the faulty key and clean the contact area. Now it works perfect again.
How is it with the membrane-style keyboards if you happen to have non-responding keys? Any chance to clean them?
Cheers
Frido
RE: Woodstock Keyboard Designs - aj04062 - 01-28-2015 01:47 PM
I don't know. That is part of my dilemma with these. I have been able to get some working a bit better by wicking alcohol in. However, if the membrane is failing, there is no cure.