HP 28 Internal Photographs?



I'm presently translating ``Voyage au centre de la HP 28C/S'' by Paul Courbis and Sebastien Lalande to English. The book contains a few photographs of the internal circuitry of the HP28C that I'm unable to duplicate.

Would any of you have--or be able to take--such photographs? In particular, I need a reasonably high-resolution picture of an HP28C circuit board with a memory module from an HP71B soldered in, as is depicted in Photo IV-3 of Part 2 of the book.

--Travis Goodspeed


I seriously doubt you'll find anybody able to supply what you are looking for. The reasoning is that the 28S/C and the 18C/19C series machines share the same hardware and as such, they cannot be opened, modified and closed back up for use. The case construction simply doesn't allow it.

IMO, it's not a hackable machine. The 48 series was far more interesting in that regard which relegated the 28 to serve only as a reminder of how not to build a calculator.


Other than the battery door, the 28 seems like a fine example of how to build a calculator not intended to be repaired, and not intended to survive more than five years of heavy usage.

(It's been many years since any company has made calculators designed to survive more than five years of heavy usage.)


At least the HP-28S _is_ hackable.

Christoph Giesselink demonstrated a wired serial I/O on the Allschwil meetings

(with an HP-28S I gave him especially for this;-)

It was possible to send data in both directions, from and _to_ the HP-28S.

The demonstation was a proof of concept, the target of interest was the HP-42S,

or more exactly to check whether it will be possible to do wired serial I/O on a 42S-like machine.

Since the 28S and the 42S are relatively similar from the I/O point of view,

and the 42S is even expandable with RAM and an optional ROM chip,

with some effort it will be possible to make the HP-42S an I/O capable machine.

The only problems are things like effort/price ratio,

or in other words: Who would pay for such modifications?

I guess the answer would be near to 'noone';-)




One good point about the HP28 series was that it did not requires a case and the alpha keyboard was distict from the numerical keyboard.


Someone posted a link to some internal photos a month or two back, as part of a thread on adding a new LCD or PCB to the 28S.
A search of the archives might bring it up.



You could buy a parts machine on an auction site...


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