HP11C Bedienungs- und Programmierhandbuch - a curiosity


if there is someone with an HP11C originally commercialized in German, I'd like you to help me satisfying one curiosity of mine. Battery changing is shown on pages 232 and 233 (May 1983, Rev. B). I have an HP11C and its back drawings are different. The ones shown are exactly the same as the HP12C's back drawing. I was told that the HP11C commercialized in German is like this. Well, I cannot say a word about it, but the statistics data in both HP11C and HP12C use different register numbers. In the German HP11C's "handbuch", the back drawing shows the HP12C's statistics registers, what is wrong.

Does anybody know anything about it?

Just curiosity.


Hello Luiz,

I have a 11C with german "Handbuch". The backside which is shown in the manual at the mentioned pages is different than the real one. Supposingly they just took the battery-change-photo from the 12C because the battery replacement is the same.

I don't know if my 11C is commercialized in Germany, but since I got it together with a german manual, I suppose that it has been selled here.

My 11C's backside exactly matches the one shown in the museum. It has also U.S.A. stamped beside the serial number.




Thank you for your answer. I believe that if it was bought in German it must be the one that's comercialized there.

Best regards!



don't know if my 11C's were commercialized in Germany,
all have the same back drawings, but these are different
than the ones shown in the manual ( e.g. 00011-90002
German 12.81 ).
That's no surprise, because the drawings in the
manual don't show the charateristical functions of the 11C,
the drawings look like short functions-charts of 12C.

curious, indeed. ( Hmm, first historical
appearance of cost reductions by Fiona ? )

thx......(h)appy (p)rogramming.....Erich N.

( BTW, Luiz, my evil 11C [ you remember ? ] has
- in the moment - the generosity to do the things
he is designed for. But he doesn't fool me, I don't
trust him anymore < crossing fingers > )


Hey, Erich;

good to know it is alive. What sort of measures did you take? What did you do? Even if briefly, tell us about it. Maybe others are curious, too... Thank you for remembering.

About the photos in the German HP11C's Programmierhandbuch: mine is dated May, 1983, and I have a Brazilian printout (original) dated 1981. I believe Fiona was not at Hewlett-Packard's office then, because good stuff came from there after this date (if she was there since then, HP was already doomed). Anyway, the Brazilian manual has the HP11C's back drawings (p. 239 and 240) intead of the HP12C's shown in the German version. I had a look at the museum's scan for the HP11C's manual, English version, and the same photos presented in the Brazilian version are there. For now, only the German manual has different images.

Best regards and a better 2003.


Hi Luiz,

OK, my best 11C is alive. What measures did I take
to achieve this ? Hmmm, nothing special. The usual procedures......remove batteries...short cut ( with [ !!! ] and without batteries inserted )...keep it in the shelf for some weeks ( without batteries )....then some day it starts breathing...until now.

I'm very suspicious about 11C's, I think they all have some
11c-specific major design or production flaw inside, concerning keyboard-control or power-supply.

happy programming..........Erich N.



As I probabyy mentioned at the time I read and answered your post, there is a common problem I found in many Voyagers, being them HP11C, HP15C or HP12C (all types): bad soldering contacts. I cannot say anything about the HP10C because I saw only one till now and the HP16C, because the only one I know so far is the one I have.

Anyway, by simply resoldering all IC's terminalsn in these machines allowed me to bring a dozen of them back to life. In many cases, the symptons used to come and go from time to time, sometimes weather dependant (metal shrinks and expands with temperature, so bad contacts come and go with temperature variations, if bad contact occurs; in Brazil we call it "solda fria" or "cool-solder", being cool a low-temperature reference, not a good-stuff reference). Have you observed this? Is it cold in Deutschland for these days? You are in Deutschland, aren't you?

Well, time will tell. I do not think the HP11C's are guitly as charged, after all. They are good, reliable calculators. Maybe after more than 12-15 years they allowed themselves to look as normal as other calculators... Who knows?

My best regards.


The most common failure in the 42S class machines is solder connections on the 8k ram chip. It seems the case back is in direct contact with the chip and any flexing and twisting of the case imparts stress on the surface mount solder pads.

Over time the solder connections fracture and leave the calculator either intermittent or completely dead. The most common failure point is pin 14, the common pin of the supply.

If you open a calculator with problems, look for the tell-tale rubbing of the chip on the aluminum esd shield mounted in the case back. 5X magnification will reveal cracked connections. Simply resolder all 28 pins for good measure. Don't attempt to resolder the cpu pins!! The spacing is too tight for manual methods and these don't fail, has there are not under stress loading from the case.


Hi Luiz,

[ bad soldering contacts ]

this would explain the behavior of this species.

[ the symptons used to come and go from time to time, sometimes weather dependant. Is it cold in Deutschland for these days? You are in Deutschland, aren't you? ]

Yes, I'm living in Deutschland. The term "cold" is a little bit cloudy, e.g I'm living in the Rhineland, here we had 10 degrees Celsius ( PLUS !!! ) last days. Same time around Berlin they had minus 6 to 10. Generally in the Rhineland we have mild winters. OK in August we had some heat, but you cannot compare this with other regions. In general we have no great changes in temperature and humity here. Beside this the calcs are used inside the house, where the temparature keeps around 18 to 20 degrees Celsius .

[ "solda fria" or "cool-solder" ]

Interesting in german we called this " kalte Lötstelle ",
i.e. cold soldering.

happy programming.........Erich N.



the correct term is "Cold Solder", not "Cool solder".

Thenk you and sorry...


Hi Luiz,

the following auction shows an 11c with german handbook and a photo of the cover:


another prove.



Hello, Holger;

based on these photos, we can also verify that the HP11C commercialized in Deutschland was made in USA. The back label is, indded, the same.


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