repair hp 27S calculator

[Bob Plachta]

I have an HP27S calculator that I've been using for 15 years. Recently the calculator started beeping when I pressed the multiply or divide keys, but still worked okay. Now those keys have started "sticking" sometimes, and I'll have to press them several times before they will display. However, they don't usually beep anymore. Now the plus and minus keys are also starting to stick sometimes, but they don't beep when pressed. Has anyone experienced either of these problems (beeping or sticking keys), and do you know how to fix them? I thought maybe circuit cleaner would help, but I can't get the calculator opened. Does anyone know how to open a 27S. Thanks for any suggestions!

[Randy Sloyer]

Circuit cleaners are not the answer. Don't go there, as they can cause more damage, depending on the formulation.

It sounds like possibly two problems.

One, a loss of connection between the keyboard and logic board. This would explain the multiply and divide key behavior. After opening, you'll have to shim the foam pad that holds the keyboard connector against the logic board to solve this one.

Two, if it beeps and displays "Memory Clear" or "Machine Reset", you might have fractured solder connections on the 8k ram chip or a bad connection somewhere. It will take at least 5X magnification to see the cracks. Very subtle.

See the Rosetta stone of Pioneer opening here: http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=5

Post again should you have any questions.

Edited: 30 July 2003, 12:49 a.m.