HP 25 and HP55

From: Joe R. <rigdonj_at_cfl.rr.com>
Date: Tue Oct 26 09:51:45 2004

At 05:35 PM 10/21/04 -0700, you wrote:
>
>On Oct 21, 2004, at 2:59 PM, Dwight K. Elvey wrote:
>
>>> From: "Ron Hudson" <ron.hudson_at_sbcglobal.net>
>>>
>>> I just got some HP calculators!
>>>
>>> Now I have some questions :^)
>>>
>>> --Anyone have a spare manual for either?


   Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha! Ha!
Ha! Ha! Ha! Ha! Ha! Ha! Go buy the CD manual set from the HP calculator
museum or else go to E-bay and be ready to pay the collector's price for an
original.

>>>
>>> --Have pointers on replacing the battery pack on the 55?
>>> (it seems to be 3 AAA nicads)

   Yes. Replace the cells with other nicad cells. Forget LiIon, NiMH and
all the other types. Buy GOOD NiCads and they'll last for many years. My
personal preference is the >>>>>>>>>> Japanese made <<<<<<<<<<<<<<<<<<<<
Sanyo batteries. Don't let them substitute the Mexican made Sanyos or
Chinese made trash!!!!! Don't let them tell you that even the Japanese
marked batteries are made in Mexico of that the Mexican made bateries are
the same as the Japanese made ones, THEY'RE NOT! FWIW I have a set of
Sanyos that I bought in Thailand in 1974 that are still useable.


>>>
>>> --Anyone have any pointers on cleaning up leaked nicad crystals?
>>> what is that stuff anyway?

   The leaked electrolyte is potassium hydroxide. The blue corrsion is
double carbonate salt of copper (from the battery contacts) and potassium.
I forget the exact chemical formula but it's something like CuKCO3. The
hydroxide reacts with carbon dioxide in the air and forms a carbonate. The
best thing that I've found to clean it up is Lime-Away. It's a product
that's sold in the gorgery stores here in the US and is used to clean up
lime and mineral deposits/stains in sinks, showers, toilets, etc. The main
ingrediant in it is phosphoric acid. Put it on full strength and let it
soak for a few minutes, then scrub it (I use an old toothbrush) to make
sure all the corrision is removed then wash well with clean water. I scrub
it while rinsing to make sure that I get ALL of the Lime-Away out. Then dry
WELL. If you don't get all the Lime-Away out and dry it well it makes
purple stains on the gold contacts when you apply electric power.

   Joe



>>
>> Most likely potasium hydroxide or similar base. You need to first
>> wash with water, then 50% mix of white distilled vinegar followed
>> by a rinse and dry.
>>
>>>
>>> I do have cases and power suplies.
>>>
>>> -- I took apart the 25's battery pack and replaced the nicads with
>>> nickel metal hydride cells (the same ones I use in my camera)
>>
>> Not a good idea. Nickle metal hydrides need different types of
>> charging. The won't last long with a NiCad charging circuit.
>
>I won't charge them in the calculator, they are regular AA cells so I
>can remove them and put them in a proper charger. :^)
>
>
>>
>>>
>>> -- Is is ok to run the 55 on wall power supply without a battery
>>> pack installed?
>>
>> Don't know. You should be able to find NiCads to replace.
>> Check out JameCo. Also, we have a place called Batteries Plus
>> that will weld together NiCad stacks.
>> Dwight
>>
>>>
>>>
>>> Will trade the 55+case+powersupply+leakybatteries(in a ziplock bag)
>>> for complete set of docs for the 25 + 1 good application book,
>>> preferably games :^)
>>>
>>>
>>
>>
>
>
Received on Tue Oct 26 2004 - 09:51:45 BST