Subject: Need info HP 28S

From: "Keys" <[email-masked]>
Date: Mon Apr 7 17:45:01 2003

Anyone know the size or type of batteries used in this model? On the back
cover it shows three batteries being used to power the calculator. Thanks in
advance

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From: Dave Mabry <[email-masked]>
Date: Mon Apr 7 17:48:00 2003

It takes 3 "N" cells.  Radio Shaft sells them, for one.

Keys wrote:
> .

-- 
Dave Mabry             [email-masked]
Dossin Museum Underwater Research Team
NACD #2093

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From: [email-masked] (Tony Duell)
Date: Mon Apr 7 18:04:00 2003

> Anyone know the size or type of batteries used in this model? On the back

Sure. It takes 3 off N size cells. These are 1.5V each. Whatever you do, 
don't use the similar-sized 12V batteries (used, I believe in some car 
alarm key fobs, etc) which will totally ruin the calculator.

N size cells are easy to obtain in the UK (even food supermarkets sell 
them), but I am told they're harder to get elsewhere.

> cover it shows three batteries being used to power the calculator. Thanks in

-tony

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From: "Patrick Rigney" <[email-masked]>
Date: Mon Apr 7 20:25:00 2003

> > cover it shows three batteries being used to power the

I have a 27S, which may or not be similar, but does take three button cells
and has markings like what you described.  Mine are MS76.  I think Energizer
357 is equivalent, also SR44.  --Patrick

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From: David Holland <[email-masked]>
Date: Mon Apr 7 20:45:01 2003

Yah, N cells sound about right, if I remember the one I used to have
many moons ago..

Careful of that fool battery clip, the plastic is _easily_ broken.  (And
much of the "cool factor" is lost by masking tape wrapped around the
thing. :-)  ) 

David

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From: Joe <[email-masked]>
Date: Mon Apr 7 21:14:00 2003

Yeah, It uses three 1.5 volt N cells. Be dammed sure you don't put in 12 volt batterirs by mistake. The batteries connect DIRECTLY to the CPU and they'll burn it up in an instant. I've had a good number of people that have tried to run them off of the 12 VDC cigarette lighter batteries and then send them to me to try and fix them but it hopeless after they put 36 volts into the CPU!

    Joe

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From: Joe <[email-masked]>
Date: Mon Apr 7 21:14:19 2003

The 27 s and 28 s are completely different models. The 28C and 28S are physically similar but the S has more memory.

   Joe

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From: Joe <[email-masked]>
Date: Mon Apr 7 21:38:01 2003

>much of the "cool factor" is lost by masking tape wrapped around the

  Good point!  The batteries have a tendency to press againt the cover and push it sideways out of it's slot. Then when you really press on it to try and close it it jams and you break it. Press the batteries into the calculator and try to keep them from pressing against the battery cover as you install it. Make sure that you get the cover lined up properly in it's slot before you press it closed.

    Joe

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From: "Eric Smith" <[email-masked]>
Date: Mon Apr 7 23:44:26 2003

> Anyone know the size or type of batteries used in this model? On the
> back cover it shows three batteries being used to power the calculator.
> Thanks in advance

N size alkaline.

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From: [email-masked] (Tony Duell)
Date: Tue Apr 8 17:18:23 2003

>   The 27 s and 28 s are completely different models. The 28C and 28S 
> are physically similar but the S has more memory. 

The 28C and 28S have the same case, and take the same cells, but the 
logic boards are very different (i.e. a 28S is _not_ a 28C with 
extra/different RAM chips added). The 28C has 3 direct-on-board chips 
under the display (CPU in the middle, 2 RAM/display drivers), and 2 
saturn-bus ROMs on the back side. The 28S is more like a 19B -- it has 2 
TAB chips under the display (which I think are CPU/ROM/display drivers, 
with the CPU disabled on one of them) and a 32K JEDEC-pinout RAM on the 
back side.

Actually, the 28C is the more expandable one. You have access to the 
Saturn bus (which can address 512K bytes), and the machine _will_ 
recognise extra RAM (e.g. taken from an HP71). There are no extra address 
lines available on the 28S CPU AFAIK, so you're pretty much stuck with 
the 32K.

I've often wondered if it would be possible to get a 28C to talk to an 
HP71 HPIL module (the hardware interface should be trivial). Of course 
writing the necessary software could prove 'interesting'...

-tony