HP-65 battery problems


I just acquired an HP-65 which works fine when running from the charger. But when I try to run it off of batteries it is dead. I know the battery pack is good because I tested it in another "classic" model and it works fine. The contacts in the battery compartment of the 65 look great--no corrosion and they have good spring to them.

Any ideas?


The problem is most likely that the gold plated contact located where the charger plugs in is not properly short circuiting the two posts it is touching. Try and pry the contact away from each post and remove any debris and clean with alcohol or contact cleaner. If it is corroded here, you may have to use some sand paper. I guess it is also possible that a wire is loose from the battery connections inside the calculator.


If the problem is the contact plate at the charger plug-in point, you can aslo check this by jumping across the two outside charger posts with a wire. This would duplicate the function of the gold contact. If that is the problem, the cleaning should do.

Alternately, I had a similar problem with my HP-65. When I bought it the battery pack was bad, so I rebuilt it. Therefore I knew that it was good. Yet when I put it in, the calculator wouldn't run off of it. I found that if the battery pack was in to far it didn't work. I determined this by putting in the battery pack without the battery door, and then turning it right side up on my hand. As I lifted up slightly on the calculator it started working normally off of the battery pack.

The final solution was just a strip of paper, the length battery compartment, folded up until it was 1/8" wide by 1/16" deep. Once this was underneath the top of the battery pack, the door could be put on and it has worked normally ever since. Hope this helps.


Thanks for the information, but I do not know anything about the wiring of the three posts where the charger plugs in. Which two of the three need to be jumpered for the test?


While holding the calculator upside down, the left and the right posts (the two that are farthest apart) are the ones you want. If you shine a light down into the plug socket, you will see a shiny metal tab hopefully touching these two posts. This metal tab is what allows the battery power to make it into the calculator, and is what Erik Wahlin mentioned might not be making a good contact.

If you jump from the left most to the right most post and the calculator works, then where this tab touches the posts is dirty and needs to be cleaned as Erik mentioned. Just be careful to not connect either of these posts to the center one, which is the opposite polarity.

Using a wire with a clip on each end will give you a secure connection while you flip the calculator over to see if it is working. Alternately, hold the wires and have someone else check the other side for signs of ife.


OK, now I think I understand what you guys are talking about. I looked at my HP-55 and I saw the springy connector tabs that get pushed out of the way when you insert the charger plug. I assume when you unplug it they then make contact with the two outer posts to complete the circuit? If this is true, then I assume the HP-65 should look the same way? If so, the news is not good--it looks like this 65 was taken apart previously and maybe the connector plate was lost or damaged because I see nothing in the 65's charger connector area that looks like what is in the 55's connector area. Any ideas on how to fabricate a connector plate?


I have a connector plate from a 67 which should work. Let me know if you need it.


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