> Does a battery have to be installed to use the 67 and/or > 97 on the AC Adapter? Someone
> told me that they could not test a calculator because they > only had an adapter and did not
> have the battery.
>
> How useable are either of these models with only an AC > Adapter and no battery?
Here is a post from comp.sys.hp48:
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From: John H Meyers <jhmeyers@miu.edu>
Newsgroups: comp.sys.hp48
Subject: Care of old HP calcs and chargers
Date: Thu, 21 Sep 2000 07:30:21 GMT
Organization: Deja.com - Before you buy.
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I'm prompted to post this by seeing old HP calcs offered for sale
with notices such as this:
"HP25C: Includes charger and battery pack, which looks fairly clean.
Compartment is clean. When I plugged it in,
I got a flashing display, then nothing."
Plugging that calc in without a good battery pack in place
would probably have destroyed it, unfortunately.
Practically all HP "LED" calculators whose charger has
only two pins depend upon a fully functional battery pack
to absorb and filter the output of the charger, which
has no internal filter or voltage regulator itself
(it is often just a transformer, no power supply electronics
in it at all).
Without the battery pack, the transformer delivers
too much voltage to the calculator; I destroyed
one or two myself before I learned better.
Three-pin chargers (HP35, HP80, etc.) are okay
(they deliver a filtered steady voltage supply for the calc,
plus another separate charging voltage to the batteries only),
but two-pin chargers are life-threatening to old HP calcs
without fresh, chargeable batteries securely in place.
Radio Shack (USA) may still be selling "Replace-a-cell"
NiCd AA-size batteries; these have the "flat tops"
exactly like the original HP-supplied
cells ("button-top" cells are slightly longer,
and will flatten and damage battery contacts
if inserted into some calc models);
cells removed from cordless phone battery packs
(often on sale at Wal-Mart etc.) are usually similarly
without the "button tops" and if so will also work fine.
In a pinch, you can, believe it or not, bang down the
"button-top" of a couple of AA-size alkaline cells
with a hammer, to make cells which will fit and
properly operate an HP calc (but you should not then
use the charger at all, because it would overcharge
and possibly cause ordinary batteries to burst).
Knowing these facts will help to preserve and increase the value
of any old HP calcs still circulating in the market, and I hope
that any sellers who read this will profit by this information
(and "save the skeets," as Tom and Ray say :)
-----------------------------------------------------------
With best wishes from: John H Meyers <jhmeyers@mum.edu>
Sent via Deja.com http://www.deja.com/
Before you buy.
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The HP-67 is not mentioned above but its charger has
three pins too.
I tested my HP-67 purchased from eBay some months ago,
without the accu-pack, at my own risk. It seems to work.
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