Spice battery connection: images


Hi, all;

about a month ago I was asked about images and information related to connections in Spice models. I once repaired one HP31E and it worked perfectly fine. I replaced the entire flex circuit for a cut of flat cable (used in computers to connect drivers). The pictures in both links illustrate the 'good' and the 'restored'.

Hope this helps those who need. (In fact, I am not sure if I sent these images to the one who asked me for them... Sorry!)


Luiz (Brazil)

Edited: 4 Nov 2005, 7:26 p.m.


You guys are one bunch of brave men...
... or insanely rich...
... or have a secret cache of old HPs! ;)


...or in the desperate need to bring a calculator back to business. qB^(

I forgot to mention that the one that's been restored had a partially destroyed flex circuit (the one that is good remains good, it is unchanged), and after the 'restoration', it worked perfectly (it was, in fact, 'dead').d8^)

I am not sure, but it seems to me you thought I removed a good flex circuit and place a cut of flat cable. q8^O If I had done such a thing, this would be the last place I'd risk (my head) mentioning the fact... That would be insane, you bet! d8^)

Best regards, Ed.

Luiz (Brazil)


Bonjour Luiz, all!

And for the fellows who already opened their calc and want to change the decimal separator, here is the picture of the jumper to cut (Europe) or solder (US). It is the LEFT one on the picture:

and how to get to it: Decimal separator change

Have a nice day!



Hello Etienne,

Nice picture! When I opened my 34C to change decimal point to comma, I took some photos too, but none are so clear as yours.

The most difficult thing was separating the case halves. I tried the dental floss trick but it didn't work (perhaps the quality of the dental floss I had at home was not so good). I found a good tip at Hugh Steers's site.

I had to rebuild the battery pack and fix the battery contacts which were broken, but the calculator worked fine until last week, when two segments ('a' and 'g' of the leftmost digit started to faint. Awkwardly only half of these segments remain lit. Now it looks like this:

­ ____
| |
| |
| |

When I removed the redish lid I noticed signs of battery leakage I hadn't notice before. Is this irreversible? It's very easy to replace the display, the problem is findind a replacement.



P.S.: This should be a separate topic, but since you and Luiz have a good experience with Spices, I thought you might help.


Hello Gerson,

If only a part of each segment does not light, then you should test the display.

Here's what I usually do (Luiz might have a better idea):

1) Take the display out if unsoldered otherwise use your probes.

2) With an ohmeter, check continuity of each display circuit track from pin to end of visible track. If a track is broken, tin it with your iron.

3) With your bench PSU at 1,5V DC (+current limit to 20mA if you can), apply BRIEFLY voltage directly to couples of the display pins.

Powering anode & cathode should (and I hope will) light the corresponding segment for each couple.

Continue till you find an offending segment.

If all segments light this way, then the problem is NOT with the display.

4) If problem is not with the display, repost here for us to go further.

5) If problem is with the display, let's wait for somebody else's idea because I've tried everything including ultrasonic cleaning with no result.

6) If nobody has a better idea, check your mail once again :-)

Best regards from France!


PS: Well, I'm getting snobish with my "PSU", a simple 1,5V battery will do ;-)

Edited: 5 Nov 2005, 12:49 p.m.


Hi Etienne, Gerson, guys;

I guess that we can point out other ways, but this one Etienne described seems to be fast, accurate and easy. I`d add that most digital multimeters can briefly lit a LED segment with their own measuring current, when set either to the highest resistence value or to semiconductor (diode symbol). In such circumstances, it is easy to see which terminal goes to each digit, and which terminal is common to each segment (I usually refer to it as `segment matrix` when teaching, as a form of comparison) hence finding the best way to test each segment faster.

About having part of a segment lit: I had problems like this one, too, and I remember that one of them was exactly doe to some sort of dust from battery leakage. I tried to remove with chemical solutions and the display was destroyed for good...d8^(

Sorry not helping too much.


Luiz (Brazil)


Hello Luiz,

Thanks for your concern. If I cannot fix it, I will send it to you (if I receive the other 34C I am waiting for), along with your book for an autograph :-)

Last year I googled for your book (Da HP41 para a HP48) and find only two left: one in Belém and the other ... in a used books store just three blocks from home! This was in fact new, from an old stock and cost only R$ 17.00 (~$7.50). I read half a dozen pages and learned something I didn't know yet about the 48.




Hey, Gerson, thanks! I appreciate your comments about the book.

In fact, my first one, writen in 1994/1995; took me three months writing, finished in January. I know that there are some `typos` and some stuff is missing, but I was so excited with the idea of having it published that I did not care too much. I remember that the revisor asked me if I did not miss something in the sentence:

"Avaliar é executar a ação associada ao objeto avaliado"

(To evaluate is to perform the action related to the object being evaluated)

He asked me "What is the action to be performed?". I thought I'd need some extra time to explain him, but I decided to ask him please to RTFM, in a polite way, of course, prior to discuss the subject... I hope I was not rude, though.

It will be a pleasure to sign your sample. Please, be my guest sending it and I'll add a few words of mine, too. BTW, have you been told about this subject? The English version exists, but has not yet been disclosed. As the Portuguese version is already available to be downloaded through the HP site, Brazil, I think there is no trouble spreading this news around, though.

About the HP34C and its LED display, I'd be more than happy to try to repair it, thanks. I am running out of free time these days, but in my vacation time I think of going ahead with some interrupted activities (good activities) related to HP calculators, electronics and the like.

Wrote too much, sorry folks.

Best regards and thanks again.

Luiz (Brazil)




Hello Ettiene,

Thanks for your suggestions. I will try them next week as I left the 34C at work (it's always on my working desk!). For testing the display, I will use a digital multimeter with diode tester.

Warm regards from Brazil!



Hi Luiz again!!

Yes, why not confess :-))

For the Spice I kept for my own use (a 31E), I replaced completely the good flex with a cut of IDE disk flat cable and soldered the display once for all.

Since then, I NEVER had to reopen it for repair.

Kind regards from France!



Hi Etienne, all;

Thank you for your very welcome additional information, Etienne. It is always good to see complementary information added this way, wiht the very intention to contribute. I appreciate that.

Merci et bonjour por vous aussi, Etienne.

Luiz (Brésil)


Hi All,

Could someone explain in details how to open up the top and the
bottom shells of a Spice? I have tried to open it up but the 2
shells are so tightly held together that I was afraid to break
or damage something.



Hi Tien,

Of course: Spice repair

Courtesy Tony Duell & Voidware.


Edited: 5 Nov 2005, 10:09 a.m.


Merci beaucoup!!

Thank you very much!!

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