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Later HP-25C Keyboard Repair - Printable Version

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Later HP-25C Keyboard Repair - aj04062 - 04-22-2013

I have a HP-25C with SN starting with 1712. It has a membrane keypad contacts similar to what you would see on later model 10 series (and 41s?).

Would any care to guess what SN and later the woodstocks were converted to this style? It has some bad traces. I need to find a donor unit (hp-21?) or repair.

Any thoughts on repair techniques and/or spare parts are appreciated.

Edited: 22 Apr 2013, 8:35 p.m.

Re: Later HP-25C Keyboard Repair - Randy - 04-23-2013

The version you have is what was used on the 30 series. Plastic domes with traces that flexed with the dome - which is the failure point.

The design was put into production with the 30 series and late 20 series before life testing was complete. When HP discovered the design was flawed, they redesigned the 30 keyboard to be the 41 metal dome style. The 20 series machines at that point were out of production and I do not know if they continued to use the faulty design for service spares (I suspect this is so) or if they went back to the original classic style metal strip key. Because of this uncertainty, I don't think you can correlate a serial number to the construction type.

If you're removing the board to repair, my recommendation would be to abandon any hope of repair, at least a repair that would have any longevity and replace with a metal strip version.

Re: Later HP-25C Keyboard Repair - aj04062 - 04-23-2013

Good idea. I think I have a couple toast 21 or 25s