Hp 65


I've just got an old Hp-65 and I have some questions if there is some specialist there,
The machine hasn't any charger, is the same of the Hp25?
There is a general key bouncing, but the keys seem to have a regular touch feel.
Is there any way to replace the battery pack for another kind of batterys?

Thanks in advance.


It needs a classioc series charger (35,45,65,67,70,80,55) Three female plugs. The 25 series had 2 prongs.

Get a pack rebuilt at batteries Plus or similar place.

Key bounce can sometimes be helped by opening and fixing the machine (be careful and learn how to do it)



Like Dave said, you need the "classic" battery pack for this one; the HP-25 uses a different kind.

One word of warning, however -- the "classic" battery pack gives you only 3 hours of power after a full recharge of FOURTEEN (14) hours. It's always seemed disproportionate to me. If you can, try to find a different solution for your battery replacement. I don't know much about these things, but perhaps the HP-65 can be used directly from the AC adapter/charger, bypassing the batteries altogether.

Can anyone elaborate, please?



Never operate a HP calc without batteries in place. Voltage surges can fry them. Calcs w/card readers and printers will be burned out when attempting to operate the motors without batteries.


Dave is right. Never operate an HP without its battery pack, as it can fry the electronics inside.

Regarding battery packs, you can get them from Mark Hoskins, eBay callsign Waterhosko@aol.com. He is a great source for batteries and spare parts, and his advice is excellent when it comes to repairing.

Repairing the 65 is much like repairing the HP-67. There is an article about it in the Articles section.


The only reason I mentioned bypassing the batteries is that I've read in this forum, repeatedly, that it can be done SAFELY with any of the "classic" HP calculators. If I remember well, it had to do with the way the recharger plug breaks the contact between batteries and CPU while the plug is in place.

I admit I've never done it myself (I used to have an HP-67 many moons ago), but it always irritated me to spend 14 hours charging, just so I could have 2 or 3 hours of operation before the "low battery" light started blinking.

At least the ratio of recharge/use times wasn't as severe for the HP-25.

About a quarter of a century ago a friend of my father's was the owner of the HP distributor in Lima, Peru. I remember visiting them very often, and seeing several calculators that were connected and working without a battery pack, while the technicians did their work.



Key bounce is simply just dirty key contacts. They are easily cleaned. A piece of fine grit emery under the contacts is all that is required to remove debounce. Just one or two passes is all that is needed. Don't over do it.

Taking the calculator apart without damaging the calculator is another trick that takes practice.

If you have the old battery pack, repairing it yourself is easy and costs less than $8. Three fine slits on the end to cut through the tabs that hold the pack together is all that is needed. 3 packs of batteries that are already welded are available. Almost dropin. Two easy solder operations is all that is required.

You can buy replacements, and save the work, but they do not have the look of the original battery pack.


If you don't like rebuilding the battery pack yourself, places like Batteries Plus and Batteries, Etc. will rebuild your pack for you for probably less than $20. They can do a much better job than you can do becuase they have spot welding equipment to assemble the packs and contacts. Welding does not risk damaging the batteries like soldering can do.

I always use nickle metal hydride cells in my packs. You can get up to three times the capacity of the normal nicads and they don't have that pesky "memory" effect where you have to be careful about charging a pack that is not fully discharged.

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