Repairing HP 20s?


Hi all,

My beloved HP 20s recently started malfunctioning. Input from the +-*/ keys was ignored, so that the operation:
2 + 2
was treated as the entry of the number 22.
I dug out the manual and ran a self test. The result was 20 - FAIL 8.

Working on the assumption that I can't send the calculator in for repair... I thought I'd try it myself. I'm posting in the remote hope that someone out there knows what this error code means, or better yet can point me to a service manual or schematic. Or can just give me any tips, such as about how to open the lid without damaging it.

Thanks much




If you really want to try repairing your 20S here's what you need to read for starters:

I doubt that HP will repair it for you as it must be out of warranty by now, but you can often find new (or nearly new) 20S's on ebay for around $30-$40.


Edited: 4 July 2005, 10:43 p.m.


Try pinching the calculator firmly, front-to-back just below the display on the right side.

If the keys work while the calc is being squeesed in this manner, you've got a common problem: an atrophied rubber pressure strip that is meant to maintain contact between the keyboard assembly and the main printed circuit board.

It's a relatively easy fix -- though perhaps more than many would care to attempt. If you don't want to try yourself, chase down Randy Sloyer (

Good luck, and let us know how it comes out.

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