HOW TO REBUILD A HP-97 BATTERY PACK



#4

I have two HP-97 battery packs that need rebuilding.One is for a HP-41 Printer and the other one for a HP-97.I also like to know if a simulator can be made in order to use the calculator and the printer without the battery.Thanks for your help,Jorge.


#5

Please be VERY cautious about running any of these products without a battery pack. In most cases, the batteries act as both a filter and a regulator. If the batteries are not connected, excessive voltages may be applied to the electronics, damaging components in an irreversible manner. You can find many messages on this same forum regarding this issue, and also on specific parts of this Museum.

Just as a suggestion, you may try with normal, alkaline batteries in place of the rechargeables BUT DO NOT USE AN AC ADAPTER WITHOUT A RECHARGEABLE BATTERY PACK.

DO NOT TRY TO RECHARGE ALKALINE BATTERIES, MAY EXPLODE.

If you plan to use an external DC power supply, BE SURE to check the following:

1) POLARITY

2) IT MUST BE ELECTRONICALLY REGULATED [VOLTAGE] (Zener diodes or IC such as LM 340 series / 7805, etc.). Normal cheap AC adapters are not well regulated, and may apply excessive and dangerous voltages.

3) IT MUST BE CAPABLE OF ENOUGH CURRENT [AMPERAGE], specially important for machines with motors and thermal printheads.

BE VERY CAREFUL. THESE SUGGESTIOSN ARE TO BE USED ONLY AS GUIDELINES AND AT YOUR OWN RISK.

#6

Use a sharp knife to slice down the joins in the battery pack. use a screwdriver etc. to separate the halves (be careful!).

Remove the cells. Note the polarity and placement of the metal contacts. Really note it! If you get it wrong you'll be sorry.

Get a new pack made up (or make it yourself from 4 sub-C nicads with solder tags).

Connect the V shaped contacts (are they the right way around -- polarity).

Make sure the bits that sto pit all shorting out are in the right place.

Note that the 4 cells are arranged in a rather non-conventional way, so if you get a pack made up from 4 cells, make sure they make it the right way!

Place cells in shell

cover with the other half

check polarity again (Just because you're paranoid it doesn't mean you're wrong).

insert in device (printer, HP97, etc)

charge briefly

turn on device (does it show some life?)

charge it completely.

There is no real need to glue the halves back together again. They'll stay together in the device. Otherwise pich the adhesive of your choice (but pick something you can disolve later if you need to re-rebuild.)


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