HP Forum Archive 08

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Help fixing HP-25 keyboard Message #1 Posted by Richard Halliwell (Australia) on 17 May 2002, 6:02 a.m. I need help to fix a faulty key on my HP-25 (owned since 1976). The '4' key does not work, except very rarely if used repeatedly. It has a normal tactile feel. I have taken the calculator apart and tried to clean the key's contacts by spraying with electronic contact cleaner through the holes under each key (this cleaner worked well on the rest of the PCBs). Unfortunatley, the keyboard can not be taken apart as it is heat-welded together (whereas I think the classics could be unscrewed). The only other problem, which I will have to live with, is that the registers and program memory don't work. I understand this is due to RAM chip damage when it was charged with failed Nicads. I have replaced the batteries with high capacity NiMH AA (1700mAh), so I hope each charge will give 10 hours of use. Hoping someone has a clever solution. Thanks Richard

Re: Help fixing HP-25 keyboard Message #2 Posted by Frank on 17 May 2002, 12:33 p.m., in response to message #1 by Richard Halliwell (Australia) Try at your own risk: I have had sucess with a strand or two of fine wire brush wire (radio shack solder brush) inserted into the contact pcb hold under the key, pressing the key lightly and burnishing the contact by moving and rotating the brush, do a little at a time then test, so you do not remove too much plating.

Re: Help fixing HP-25 keyboard Message #3 Posted by Richard Halliwell (Australia) on 18 May 2002, 6:35 a.m., in response to message #2 by Frank I will give it a try - I guess I can hardly make it any worse. Thanks for your prompt reply, shows how worthwhile this forum is! Richard

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