Clamshell, shucking the clamshell, any thoughts!


Starting the clam shell with a non-functional 18C and a partially functional 28S

I am thinking it is the foam compression strip for the connectors on both, but, this means an operation.

I have searched the web and the only thing I see is a discourse with Tony Duell and others about heat stakes. Tony mentions that the heat stakes in this case are required to hold the upper and lower halfs together and there fore just breaking into it as some do with the pioneers is a no-no.

He recomends that the keyboard overlay be removed and the heat stakes drilled out in a careful manner, leaving enough for a good snap back into position.

My question:

Anyone out there done this or tried SUCCESSFULLY any other method?



Someone here once posted that he cut the cap portion off of the stakes while leaving as much of the projection of the stem as he could. Then he slid the pcb off/up. He mentioned that this took a lot of time and care, but it left just barely enough stem to melt back down over the pcb one time. I never tried this. Never had the patience.


Think you nailed it,

patience!!!! Well, I will lift the keyboard bezel off to expose the stakes and take it from there. Maybe I will end up with a fixed calculator or a spare battery hatch at worst.

Cheers, Geoff


I think that the highest use an algebraic 18c can be put to is to be the battery door donor for an RPN 28 C or S that needs one.


Unfortunately, about the only reason a 28C or 28S will have lost its battery door is because the plastic of the calculator *around* the battery opening has cracked or broken away. AFAIK, nothing can repair the real problem that would be worth the effort. Replace the missing door, and you're left with a permanently disfigured calculator that is very likely to lose its new door sometime in the future for the same reason the first door was lost.

A really nasty mechanical/industrial design, those clamshells!


You also need to lift the label above the display there is 10 heat stakes across the middle of the battery compartment. If you like I can send you pictures of a 28S I have open, and you can see what you are up against. I pried it apart without doing any damage to the case or the electronics inside. It still works but I have not put it back together as I need the hinge piece and I have not been looking too hard for a donor as I have another 28S in good condition.


Hello Paul,

Some pics would be highly appreciated. I have three non functioning to partially functioning clamshells aquired for the clamshell chapter in the book.

So by hook or by crook I will be operating on them. Of course any info in advance would be extremely appreciated. Pictures; YES!

Cheers, Geoff




Hi Geoff, I tried to transplant working 28S guts into the shell of another 28S (a case where a 'mint' 28S didn't work and its beaten up cousin worked fine but wasn't nice to look at).
It is a very fiddly job - the clamshells were not designed to be taken apart *ever*. In my case, I did manage to do the transplant, but it is hard to get the stakes to reattach to the new donor because you lose some of their length when you drill them out. You need to use a soldering iron on low strength to reattach them.
I do know someone who does have the patients and is very good at it though. I can ask if he is willing to help. Cheers, Keith


Thanks for the info and the offer Keith.

Must do the operating for the book and document each step so I will be doing the procedure here.

Cheers, Geoff


A blast from the past on HP-28 disassembly can be found here, courtesy of comp.sys.handhelds and Google Groups, in case it's of any use.


Edited: 31 May 2011, 6:01 p.m.


Thanks Bob!

These look like the worst of the entire HP family to get into, considering the relavent postings.

Now were talking about saws and the like. It is almost as hard as the HP01:



I wouldn't take that old USENET post as appropriate for our age. Plasma cutters have gotten a lot more affordable in the ensuing 20 years :-)

Edited: 31 May 2011, 9:14 p.m.


I guess you can also use the mini tractor beam from the Starship Enterprise to hold it still too! ;)

Possibly Related Threads…
Thread Author Replies Views Last Post
  "A Penny for your thoughts" on the HP50g Tom Grydeland 3 1,716 08-01-2013, 03:57 AM
Last Post: Les Koller
  A Non-Graphing Calculator with CAS? Thoughts...? mr-scorpio 1 1,035 02-17-2013, 01:02 AM
Last Post: Les Koller
  Exotic Clamshell collection Keith Midson 7 2,381 07-31-2012, 06:57 PM
Last Post: Keith Midson
  [WP34S] Beginner's positive thoughts - 1 week in. Chris Tvergard 7 2,389 05-14-2012, 03:35 PM
Last Post: Walter B
  Re: [WP34S] Beginner's positive thoughts - 1 week in. Chris Tvergard 2 1,437 05-13-2012, 06:50 PM
Last Post: Chris Tvergard
  thoughts about HP-35S P<-->R Matt Agajanian 3 1,313 04-07-2012, 08:47 PM
Last Post: Matt Agajanian
  Clamshell Battery Contact Repair aj04062 6 2,098 03-03-2012, 11:21 AM
Last Post: aj04062
  Clamshell Battery Contact Repair aj04062 11 3,351 02-23-2012, 08:23 PM
Last Post: aj04062
  HP 41CL; requirements and thoughts about donor shells Geoff Quickfall 11 3,286 12-06-2011, 11:04 PM
Last Post: Randy
  15c LE thoughts kc 20 4,506 10-20-2011, 01:14 PM
Last Post: Ethan Conner

Forum Jump: