HP42S upgrade and opening... pictures ;-)


Just a short note.

It was brought up that opening a Pioneer by removing the keyboard overlay and then drilling the eight heat stakes may be risky or destructive. I thought I would post these results to let you be the judge.

I tried the force full pry technique on a 48SX and was not happy with the results. Suffice to say it is working, looks good, but now has a wavy keyboard due to the forceful separation of the shells without predrilling.

Now when I say drill out the heat stakes I mean just enough to separate the shells and yet provide a snap back into position without the aid of glue.

Here are some shots of the procedure. I have completed 3 restorations and while inside the 42s I also upgraded the memory to 32K. Of course this will all be found in the book in greater detail 8-)

By the careful application of a little heat to the keyboard (warm but not hot to the touch), just enough to soften the glue you can pry the overlay off the calculator starting at the bottom as pictured. Note the flaked paint at the lower right hand corner.

'Calculator one' non-functional with corroded overlay:

While peeling the overlay back, do not bend it at such an angle that it creases.

'Calculator one' non-functional with corroded overlay. This calculator still needs the overlay touched up but has had the contact foam replaced, keyboard circuit cleaned and memory upgrade:

Here is a shot of two overlays looking at the back. The one on the left has had the adhesive removed. Once off, the overlay can be placed between two vinyl sheets on a flat surface. By rubbing a large spoon, bowl side touching the vinyl, the overlay can be flattened as seen below. Of course do not flatten the factory folds! The one on the right has not had the adhesive removed or been flattened yet.

The overlay pictured below had some corrosion on the bottom right corner which had caused flaking paint prior to it's removal (see above). I am currently experimenting with paint but need an airbrush to correctly and invisibly apply it. At the moment the overlay is flat and crease free and could be placed back on the calculator with contact cement. Note the available memory!

'Calculator one' with corroded overlay:

The offending foam used for pressing the keyboard flex PCB into the logic PCA:

The heats stakes under the overlay prior to drilling:

The heats stakes under the overlay after drilling, you can see just how little needs to be shaved off the top of the heat stake:

Of course what good is all this unless you have an after picture. This is one of the three. It had and almost perfect keyboard and I was reticent to open it up until I had experimented on the two non-functioning beat up versions.

Minty version with six small glue dots. This was used by a company in Britian that had overlays produced and then affixed to the keyboard overlay with six small dots of glue. I have removed as much of the glue that I can (mechanically) without harming the overlay. Both the next pictures show completed upgrades and restorations. The memory of 27,xxx reflects the available memory after the upgrade and my suite of progams have been loaded:

Here is a shot of a beat up version. The overlay was removed, keyboard cleaned as well as PCA and LCD panel and the offending degraded foam was removed which supplies the force to allow the keyboard flex PCB to contact logic PCA. The memory upgrade completed and then the whole thing bundled up. This overlay had dents and scratches. The spoon and vinyl method removed the dents and flattened the overlay after the adhesive was removed. The scratches were touched up with a combination of black and brown felt marks.

'Calculator two' non-functional with scratched and dented overlay. This calculator also had the overlay touched up, contact foam replaced, keyboard circuit cleaned and memory upgrade:

All three calculators snapped together with a healthy 'snap' yet allow me to open them if required. The overlays were affixed to the calculator with contact cement judiciously placed on the both surfaces.

I think they turned out alright and it is my opinion, having opened stretch and normal pioneers, that I prefer the keyboard overlay removal and heat stake drilling. If you try this experiment do it on a TOTALLY dead HP pioneer.

Cheers, Geoff

Edited: 26 Oct 2009, 9:03 p.m. after one or more responses were posted


Hello Geoff,

Absolutely nice and documentary your albums at photobucket!!!!

I have seen HP images WOW...nice work!

these images are of a 42S opened via Credit Cards ;)

Look at the undrilled Stakes.



Hello Nacho,

Nice work. I will be trying the credit card method on an HP48SX with bad keyboard flex PCB and logic PCA contact. The foam again!

I will let you know how it works. I will also include the technique in the book as an alternative.

I can't read the RAM chip, did you upgrade the calculator RAM to 32K?

Also, did you remove the LCD for swapping purposes with one the worked?

Also, did you modify the stakes for re-assembly as I have found they do not go back into their holes easily, at least on the 4 I have done with the pry apart method. I had to shave the mushroom head shape (narrow it) before they would snap back into place.

Cheers, Geoff

Edited: 19 Oct 2009, 12:50 a.m.


Hello Geoff!

I did not any upgrade to the 42S!

I removed the LCD because I cleaned all the Keyboard and Overlay intensely, they were plenty of dust!

I put the Keyboard in a recipient with distilled water and then with some neutral soap and a toothbrush I cleaned all the keyboard and overlay. A shame I did not the before pics.

To do a re-assembly I have always to shave the mushroom head shape, if not, it is impossible to assemble it well.

The calc was not very well treated, but now ( the calc ) is living a 2nd life.



Edited: 19 Oct 2009, 4:08 a.m.

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