How does the HP 42S come apart?

Anyone have any experience with repairing these?



Not so much repairing, as upgrading, but that involves taking them apart.

The case is heat-staked together, like most recent HPs :-(. The stakes are in the battery compartment, and under the metal overlay.

Take off the battery cover and cells. I find it best to carefully peel off the overlay -- use a thin screwdriver worked across the machine between the rows of keys. Don't try to pull it up starting at one end, that _will_ crease it. Then cut off the top of the stakes with a 3.5mm twist drill bit held in the fingers. The case will now open.

For _my own_ machines, I just clip the case back together. I find it says together well enough, even without the stakes, to stand up to the usage I give the machine.

Others have said you can leave the overlay in place, drill off the tops of the stakes in the battery compartment, and then pull the machine apart, breaking the stakes at the front edge (the tops of which are under the overlay). While this preserves the appearance of the overlay, I feel the forces involved could damage the keyboard or even the PCB, and I prefer to have a working machine to one that looks perfect (as I've said here and elsewhere, I don't really care what my machines look like).

On the main PCB there's a large TAB chip (CPU, display driver, ROM, etc), and a 8K*8 SRAM chip. Oh, and a few small components, IR LED, etc. There's not a lot to repair. What's the problem with your machine?


Our friend Paul Brogger has posted extensively on repair of pioneers. Search the archives, plus see these two articles:

Pioneer "Observational Internals"

Increasing HP-42s Memory to 32K


Thank you very much for the ine info, Tony and Jeff.

Thanks also to Paul.

The 42S? D.O.A. (for now... ;-)



In my case something fell on the calc and now none of the keys 3 rows to the left dont work. May be a simple enough repair. What do you think.


The keyboard contacts are contained in a multi-layer mylar "sandwich" with a 15-conductor edge connector. That connector's contact with the PCB is maintained by a rubbery cushion that sits a bit below the display, above the top row of keys, and behind the case front. (Don't confuse this with the longer, thinner, also rubbery LCD contact strips running above & below the LCD.) If you're living well, removing the PCB will allow you to beef up the cushion strip and re-establish keyboard contact.

I'm one who does NOT remove the overlay -- and I claim I've never damaged a Pioneer by taking it apart the other way. (That is, drilling the stakes in the battery compartment, then prying the case halves apart with my fingers.)

Read the two articles (linked-to elsewhere) and ask questions as they arise. Good luck!


Hi Paul.

THANKYOU very much (!) for your reply...
Very cool answer.

There is certainly a bit of Art to doing repairs on these babies, isn't there? (Even the 41 has a few tricks, traps and pitfalls)

I will certainly write if/when I need to as I go.


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