HP-28S with User and Advanced Reference Manuals

[rprosperi]

(02-24-2017 10:59 AM)jebem Wrote:  It's kind of intriguing that a calculator such as the HP-28S can be found for low prices in eBay and in local auction sites like in Portugal, Spain and France.

I was checking the sold items on eBay for this model, and perfectly good working units were sold for very low prices indeed, even including the s&h.

It seems to be a very common model to find for sell everywhere.

All of the clamshell design models (except very late-production 19BII) suffer from an amazingly poor battery door design - easily the worst of any HP models - which result in almost all units having some level of broken plastic in the areas around the perimeter of the battery bay; sometimes it's only cosmetic (but always visible due to it's location, but even can get to the state that the door will not stay closed.

Collectors don't trust vague descriptions and poor photos, even with comments that say "battery door OK", etc. As these machines get older, the plastic becomes more brittle, and risk of damage increases, even with careful use. Since machines are already broken, or likely to break soon, prices and demand are not high. (But this is good news for collectors if you plan to simply display or store the machine).

It's too bad too, as the business models are excellent machines, with Clock, Solver, trig functions, etc. and also including a simple text editor to take notes (leveraging the dedicated alpha keyboard).

The 28C and 28S aren't bad for early RPL (though 28C has such limited RAM you can't do much with it) but without I/O to load/save programs or backup, it's just a no-brainer that a 48/49/50 is the way to go.

Very late-production 19BII models introduced a totally different battery bay/door design, which was accessed from the rear of the machine. (Note: even this design wasn't great as the door release clip could easily be broken if squeezed too hard). On auction sites, these "rear door" models typically sell for at least $100 more than the earlier type, for similar condition machines.