How to open HP-28S?


Has anyone had any experience opening a HP-28-S?
I am unclear if the keypad with display is snapped, glued or heatstaked in place. Thanks.


My son's 28s fell apart -- apparently it had been flexed to death stuffed in his backpack with all his high school books.

The keyboard faces are snapped into the two "backs" (one is actually the "front" . . . ) and held in place by an array of plastic front-to-back pin-and-socket connections. (There are LOTS of 'em -- I'll be able to give more details on Monday, if I remember.)

I seriously doubt that the connections will snap apart without breaking a great many of them, but I haven't yet tried to take a working machine apart.

On my son's broken unit, the left-hand (alpha) keyboard was coming apart, and the keys were dropping out. I popped it apart the rest of the way, and took the opportunity to pop apart the right side too, with its PCB, battery contacts, & etc. I believe that some of the pins are still intact after my "surgery", but not many. (I just don't know how many of them were already broken at the time I started in.)

I'll take another look, and if no one has given a more detailed description by Monday, I'll try to do so.

Good luck!


..., would you send a photo (have a digital camera or a scanner?) of the open halves of the calculator's case, so we (me) could have a look at the joining pins. Is it possible?

I've read some posts about opening 48's and at least one about the 28, but I have not seen yet a photograph of an HP28 opened. The only one I have is the one at Hewlett-Packard Journal, August 1987, but is not intended to show the pins, it's a front-taken photograph.



Will do -- It'll take a few days . . . I've got a conventional ("chemical"?) camera only, but can scan the prints once they're available.


Thanks alot! I really appreciate the help.


I didn´t get it... Have you found the article about the HP28 in the Hewlett-Packard Journal? Did it help you anyway? Or you are waiting for the inside photo from Mr. Brogger?

Just to figure it out...


No, I do not have the article.



If you are interested on (it explains a lot about the HP28S production line, a bit of internals, some about RPL), I have scanned the pages. Just send an e-mail and I'll send them to you. I'll try enhacing the "exploded" photo if you want too.


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