HP 48GX Ram Cards

[XizDaqrian]

Hi all,

I've been checking eBay, CraigsList, HPCalc, etc for RAM cards. I've
read some of the online discussions about voltages, etc. Does anyone
here in the know have any info about the following type of card I saw
on eBay?

HP/Agilent 85700A RAM Memory Card, 32kB

I would ideally like to get more than 32kb, but we crawl before we can
walk, now don't we? The prices of these RAM cards are outrageous for
the most part. I don't know how some of these dealers sleep at night. /
end soapbox

I know HP was making cards which were about the same for other
devices, but don't match the specs. Thanks in advance all.

[John H Meyers]

On Mon, 03 Aug 2009 22:11:26 -0500, XizDaqrian wrote:

> I've been checking eBay, CraigsList, HPCalc, etc for RAM cards. I've
> read some of the online discussions about voltages, etc. Does anyone
> here in the know have any info about the following type of card I saw
> on eBay?
>
> HP/Agilent 85700A RAM Memory Card, 32kB

http://www.4gte.com/EquipmentPages/85700Amemorycard.htm
http://www.4gte.com/partsagilent5.htm#85702A
http://www.electronicspoint.com/advantest-memory-card-t102941.html

Are these the same cards used in original HP48 calculators? (see below)

> I would ideally like to get more than 32kb, but we crawl before we can
> walk, now don't we? The prices of these RAM cards are outrageous for
> the most part. I don't know how some of these dealers sleep at night. /
> end soapbox
>
> I know HP was making cards which were about the same for other
> devices, but don't match the specs.

IIRC, Epson (OEM) made the calculator cards for HP and for EduCALC (and Sparcom?)

They were said to be originally designed
as removable storage for electronic typewriters,
and HP chose them, at that time,
as suitable for original HP48 series calculators.

HP required spec changes from Epson,
to suit different voltage levels in the calculators,
and exclusive distribution of some capacities of cards made to HP's specs
(1MB, maybe 128K?).

Without the spec changes, an original, unmodified card might,
under adverse conditions, short out the calculator power supply,
due to "static protection" circuitry that deliberately shorted
the card pins when the card "thought" that it was unplugged.

"Grid" brand computers also adopted the same Epson typewriter cards as storage,
but did not modify the original specs -- consequently,
there were various sources of original, unmodified Epson cards,
which were bought anyway by some HP48 calculator users,
either not knowing or disregarding the risk.

Example of "close call" incidents with "Grid" cards:
http://groups.google.com/group/comp.sys.hp48/msg/85fc3c24a49d3265

> The prices of these RAM cards are outrageous for the most part.

This was even said when they were in production and sold by HP:
http://www.hpcalc.org/hp48/docs/faq/48faq-12.html#ss12.4
(also explains how unmodified cards may damage calculators)

Once things are out of production but still in demand,
then they sometimes become like tulip bulbs :)

http://www.uglychart.com/2004/09/26/sir-isaac-newton-tulips-and-real-estate/

When original HP48 calculators were more common,
a few private entrepreneurs once built and sold cheaper RAM cards, up to 4MB?
(the "maximum" capacity actually can not be entirely used, due to a bug),
often sacrificing the shielding (and the possibly patented Epson "shutter");
is anyone still at it, opening the dusty box in their garage for special orders?

[r->] [OFF]

[XizDaqrian]

Thanks for another fantastic answer John. That was the rest of the
story! I'm gonna call you Paul Harvey. Thanks again.

[John H Meyers]

On Wed, 05 Aug 2009 12:56:28 -0500:

> That was the rest of the story! I'm gonna call you Paul Harvey.

That would be quite a long distance call,
like this one, containing a deeper story than ever found here:

http://www.youtube.com/watch?v=aYEFkYtANVg

Have another level, from Mohandas K Gandhi, recorded in 1931:

http://www.youtube.com/watch?v=dk_RtLayZqY

-[ ]-