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Walterthomas · 02-08-2016, 08:40 PM

I had a battery leak and corroded one of the contacts. I cleaned the contact and the HP works fine. My problem is every time the contact corrodes or I replace the batteries I get "Memory Lost" and the programs I have in the HP are gone.
Is there an internal battery or something that maintains enough juice to retain the memory when the batteries are replaced?
If yes, can it be repaired?
I did a search for internal battery HP41 and got no results.
Thanks in advance.

Steve Simpkin · 02-08-2016, 08:43 PM

There is no internal battery. There is a small capacitor that retains the memory contents while changing batteries. This is intended as a short term power source only.

Walterthomas · (This post was last modified: 02-08-2016 09:11 PM by Walterthomas.)

Ok, I don't use it very often and I guess the one battery contact corrodes and it's not getting enough power long enough to lose the memory.
Guess I will have to remove the batteries and clean the contacts weekly.
Thanks.

**rprosperi** · 02-08-2016, 09:58 PM

(02-08-2016 08:45 PM)Walterthomas Wrote: Ok, I don't use it very often and I guess the one battery contact corrodes and it's not getting enough power long enough to lose the memory.
Guess I will have to remove the batteries and clean the contacts weekly.
Thanks.

The internal capacitor will keep the memory intact for longer than you might guess, at least 30 seconds (though some folks have reported up to days without loss), so if you change your batteries fairly quickly, you should not get a ML. If you are swapping quickly, but you still get ML, then it is likely that the damage done by the corrosion is preventing good contact in general. If so, try cleaning the contacts and then treat them with DeOxit Gold contact cleaner and preserver. It's not a gimmick, it really works well, and the small bottle will last a LONG time as very little is required. It can be use for all kinds of contacts in many devices around the house or shop.

quantalume · 02-08-2016, 10:00 PM

If you start with fresh alkalines and use your calculator often, then it should run the batteries down before they leak. Definitely turn on the calculator at least once a month to see if the batteries have become discharged. The HP-41 draws power to maintain RAM contents even with it turned off. I recommend you remove the batteries after the date printed on them, regardless of whether or not they still have a useable charge. I don't recommend no-name batteries without dates.

Steve Simpkin · 02-08-2016, 10:19 PM

(02-08-2016 09:58 PM)rprosperi Wrote: ... (though some folks have reported up to days without loss)...

Indeed. I store my HP-41C without the battery holder installed since I very rarely use it. One time when I put the batteries in and fired it up I was shocked to see my test program still intact after approximately 4-5 months of storage without the batteries installed! My experience aside, HP never guaranteed it would hold the memory for more that the few minutes it took to change the batteries.

I second the recommendation for DeOxit Gold contact cleaner. This product forms a protective anti-tarnishing layer on the contacts that helps prevent oxidation.

damaltor · 02-09-2016, 11:06 AM

(02-08-2016 09:58 PM)rprosperi Wrote: ...(though some folks have reported up to days without loss)...

I removed the battery pack, and had none in there while building a new rechargeable pack. I left the calculator sitting over the weekend without power supply and without battery, and when i wanted to put the finished battery pack in i remember that i definitely pressed on a lot of keys before inserting the new pack. The calculator started without memory loss and all programs were still there.

ElectroDuende · 02-09-2016, 02:39 PM

(02-09-2016 11:06 AM)damaltor Wrote: I removed the battery pack, and had none in there while building a new rechargeable pack. I left the calculator sitting over the weekend without power supply and without battery, and when i wanted to put the finished battery pack in i remember that i definitely pressed on a lot of keys before inserting the new pack. The calculator started without memory loss and all programs were still there.

As far as you don't press ON, it will keep your data for a long time.

damaltor · 02-09-2016, 09:16 PM

(02-09-2016 02:39 PM)ElectroDuende Wrote:
(02-09-2016 11:06 AM)damaltor Wrote: I removed the battery pack, and had none in there while building a new rechargeable pack. I left the calculator sitting over the weekend without power supply and without battery, and when i wanted to put the finished battery pack in i remember that i definitely pressed on a lot of keys before inserting the new pack. The calculator started without memory loss and all programs were still there.

As far as you don't press ON, it will keep your data for a long time.

I think i did - i wanted (!) to clear memory because i wanted to start with a fresh system, as i wanted to write a test program to test the quad mem module i got. So i thought to myself, i had the battery out now for 3 days, press a few keys to be sure the memory is cleared. Also i am pretty sure i pressed on, because i pressed the first two or three columns of keys from top to bottom.
Might be that my memory is wrong though, and i missed ON...