Low Battery Asterisk - HP10C

[John Cadick]

I just bought a 10C. It seems to work well; however, the low battery alarm asterisk is flashing almost constantly. I have put three new sets of batteries in it. The last were brand new silver oxide.

When I first installed the new batteries, the asterisk disappeared until I had done a few calculations. But then it came back with a vengeance.

In addition to replacing the batteries, I have cleaned the battery terminals in the calculator. They seem to making good contact.

I have searched the museum and the voyager series literature but haven;t found any suggestions.

Anybody have any thoughts? The serial number is 2248A11157. It is stamped USA.

John

[rprosperi]

(03-24-2017 04:16 PM)John Cadick Wrote:  I just bought a 10C. It seems to work well; however, the low battery alarm asterisk is flashing almost constantly. I have put three new sets of batteries in it. The last were brand new silver oxide.

When I first installed the new batteries, the asterisk disappeared until I had done a few calculations. But then it came back with a vengeance.

In addition to replacing the batteries, I have cleaned the battery terminals in the calculator. They seem to making good contact.

I have searched the museum and the voyager series literature but haven;t found any suggestions.

Anybody have any thoughts? The serial number is 2248A11157. It is stamped USA.

John

That's a very old 10C, made shortly after introduction. These old ones have the battery contacts that are relatively 'flat' (vs. the later larger spring) and I've found that if battery corrosion gets into the spring contact, it can prevent good contact. Try some DeOxit contact cleaner.

Also, verify the voltage of all 3 new batteries BEFORE inserting them; if good, insert them and use the machine until the annunciator comes-on, then remove them and verify voltage again. Try to keep track of which battery was where, as another recent post reply indicated that could reveal where (which contact) the trouble is (possibly shorting).

Also, while batteries are out of the machine, short the terminals to drain any residual voltage (or is it current?) in the machine.

In the past, when I was sure I had a bad Voyager machine with same symptoms, it turned out to be only several bad batteries purchased in the same batch. Maybe you'll get lucky too.

[Geoff Quickfall]

What Bob said!

Some batteries have very flat -be ends also. That causes the negative end battery to calc contact to short and prematurely drain at the contact end.

[John Cadick]

I knew that the calc is pretty old, and I have never seen battery contacts like these. (Photo attached.)

There are three contacts on each end of the battery compartment, but I have no idea why they are arranged like they are.

Should all three of them be making contact with the battery terminals. What am I missing/

john

[John Cadick]

Sorry. I forgot to attach the photo.

J

[rprosperi]

(03-24-2017 07:39 PM)John Cadick Wrote:  Should all three of them be making contact with the battery terminals. What am I missing/

I have a similar age 10C I just examined (though all early Voyager models should be the same), the contacts look the same. If old batteries have leaked in the bay in the past, sometimes the dried battery crud surrounds the leads and prevents contact. Again, a gentle clean with DeOxit will remove the crud and prepare the surface of the leads.

On mine, on each end, the 2 outer leads/contacts seem to extend inwards (towards the opposite end of the battery bay) more than the center one, at least making it appear as if only those leads 2 touch the battery. Can't tell for sure once the batteries are in place.

I can't tell from the photo if your leads are the same, but if not, VERY gently pry the 2 outer leads upward (away from the wall) using a dental pick, fine-point tweezers, etc. But I'd try simply cleaning and testing with known (voltage tested) good batteries first.

[John Cadick]

Thanks, Bob. The center lead on both ends is pushed outward -- away from the batteries. Each one looks like it is very close to if not resting on the plastic. The other two are pushed inwards -- towards the batteries. They are about equidistant from the end of the compartment.

The batteries don't seem quite as tight as the other Voyagers that I have. Perhaps with time and/or over-zealous owners, they have been bent a little too far outwards.

A close inspection with a magnifying glass shows very little corrosion or contamination on the terminals. I have cleaned them once with CRC contact cleaner. I cannot find my DeOxit Can nor can I find my contact burnisher.

In my early years, I was a protective relay engineer and have done a LOT of contact cleaning. I'll see if I can't scare up the DeOxit and my burnisher. Also, maybe a little VERY gentle manipulating to get all of the contacts a few millimeters farther in.

I'll keep you posted on my results. Thanks for the help.

John