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HP-28S with User and Advanced Reference Manuals
08-10-2016, 03:56 PM
Post: #1
HP-28S with User and Advanced Reference Manuals
I have for sale a USA made 28S that's in good condition. The battery door is still tight, although I would recommend holding it while you close the calculator.

There are very few dings on the case and the screen is free of scratches and haze.

I will include both the User Manual and the Advanced Reference Manual.

I bought it but didn't use it much because I'm addicted to the red glow of the classics.

$150
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02-22-2017, 07:13 PM
Post: #2
RE: HP-28S with User and Advanced Reference Manuals
Any interest? I still have this for sale.

How about $100?
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02-22-2017, 08:44 PM
Post: #3
RE: HP-28S with User and Advanced Reference Manuals
PM sent

Saludos Saluti Cordialement Cumprimentos MfG BR + + + + +
Don Luigi
KindleFire7 Free42 '<3' I + + +
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02-23-2017, 08:49 PM
Post: #4
RE: HP-28S with User and Advanced Reference Manuals
Thanks for the pictures you sent to me via email, Dan.It is nicely preserved and in good shape!
I have been doing the numbers and import taxes and shipping from the USA will finally add too much onto the price. I am not in a hurry, it was meant as a second unit in my little collection. I think I will wait until a seller from Europe pops up.
I wish you good luck with the sale of that beauty. 73&DX ;O)

Saludos Saluti Cordialement Cumprimentos MfG BR + + + + +
Don Luigi
KindleFire7 Free42 '<3' I + + +
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02-24-2017, 10:59 AM
Post: #5
RE: HP-28S with User and Advanced Reference Manuals
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.

Jose Mesquita
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02-24-2017, 09:26 PM
Post: #6
RE: HP-28S with User and Advanced Reference Manuals
(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.

--Bob Prosperi
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02-24-2017, 09:44 PM (This post was last modified: 02-24-2017 09:47 PM by revwillie.)
Post: #7
RE: HP-28S with User and Advanced Reference Manuals
I got a 28c for $40 on ebay last year. Maybe I was just lucky, but the battery door is pristine and it was very clean all around. The seller had installed new batteries. I opened the battery door just out of curiosity, but I'll resist the temptation moving forward. Personally, I prefer the 42s for ease of use. RPL is obviously powerful, but there's a learning curve. $150 is a fair price for a 28S if it is still like-new. Also, it looks like manuals are harder to find and DanLewis was including two original manuals.

Was the 28c the first hand-held graphing calculator?
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02-24-2017, 10:26 PM
Post: #8
RE: HP-28S with User and Advanced Reference Manuals
Thanks for your explanation, Bob.

I guess that there are very large quantities of these machines in the market and it helps to lower the market value a bit as well.

In 2014 I bought one pristine, almost new in the box, complete with manuals (although in Brazilian Portuguese language edition) HP-28S for just 40 Euros.

The original owner paid 31260$00 Portuguese escudos in 1991 (about 160 Euro) from a HP dealer in Porto city.

I don't even try to insert batteries in it because I know the battery door can break at any moment, even if it was rarely used before. If it breaks, its value will be close to zero these days.

Jose Mesquita
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02-24-2017, 10:28 PM
Post: #9
RE: HP-28S with User and Advanced Reference Manuals
(02-24-2017 09:44 PM)revwillie Wrote:  Was the 28c the first hand-held graphing calculator?

I was under the impression that the first ever graphical calculator was a CASIO fx-7000G model, but I might be wrong.

Jose Mesquita
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02-27-2017, 02:57 PM
Post: #10
RE: HP-28S with User and Advanced Reference Manuals
Since it's obvious to me that these are going for less than I have listed it, a price reduction is in order: $75
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03-03-2017, 02:06 AM
Post: #11
RE: HP-28S with User and Advanced Reference Manuals
You have a PM from me.
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