HP 41CX halfnut


Hello out there!
Can someone tell me exactly why HP made the 41, 41cv adn 41cx in regular and halfnut versions?
What evactly (besides the processor board and the display) is really improved/ better /worsws than the regular one?
Thank you all for your time in advance with this question,


Hi Ted

Supposition on my part, but I beleive the halfnut has a lower component count so I'm guessing that Norm's friends, the beancounters and MBAs, at HP changed to the halfnut as it was cheaper to produce.

From comments made on this board, it appears that halfnuts may be more reliable (although my two fullnut CVs - ebay purchases - appear to be fine with no problems even after a trip across the Atlantic (so far - touch wood) BUT the fullnuts are a lot easier to repair as they can be disassembled more readily (not that I've tried).

Functionally I don't think there's much difference, opinion seems to be divided as to which display is preferable but the halfnut display is optimised for viewing at an angle (machine lying on the desk) whilst the fullnut is easier to read from a 90 degree angle (machine in your hand).

Apparently the halfnut can also display lower case characters but this requires machine code (mcode) programming techniques, eprom burners, et al so isn't a practical difference for low tech guys like me.

Hope this helps with a bit of info until the experts can reply.


PS see also in the latest archive





AFAIK, James pointed out almost all user-related differences and their reason. The only two extra points are:

- key-feeling: halfnuts' keys are a bit "harder" to punch because of a thicker rubber sheet between the keys and the keyboard
- display contrast - using the same extra ROM mentioned by James, you can adjust halfnut's contrast and consequently their viewing angle, not available in fullnuts' LCD.

It's a fact that many other hardware related aspects are not even known, or disclosed as information, but what we can say by observing and describing is about that.

Just an extra 1¢.

Luiz C. Vieira - Brazil


Semiconductor technolgy was expanding so quickly at that time (really just getting into the curve that we are still enjoying), plus the 41C family were in production for so long, that it would have made perfect sense to have changed the design several times as HP did. Cost reduction is almost always reliability improvement. Number one is reducing the number of IC package pins involved (by putting more functions in one chip) because every time a wire is bonded to an IC, the die suffers a severe shock that can ruin or weaken it. This also reduces the number of solder joints which are a potential source of un-reliability. Keeping more functions on a chip reduces total current consumption because the signals that have to go to external pins need relatively high powered drivers to charge the capacitance of PCB traces, which aren't required for internal nodes.

Eliminating some PCB traces also improves radio frequency interference (reduces radiation - makes it easier to pass the test!) FCC and other regulatory compliance can add a lot to the engineering cost because it can require redesign and additional tooling. One Tandy computer that was designed with a plastic case (the last one, I think!) had to have a number of internal sheet metal shields added at the last minute - each one recommended by a very expensive consultant! Shortly after that, the entire department spent two days in school taught by that consultant, learning how to design for compliance.

Also, as semiconductor technology advances, as measured by the "microns" (gate length?) which are always always getting smaller, it is not possible to continue manufacturing older designs - the new equipment is tuned for the new, smaller geometry. So chips that stay in production for extended periods have to undergo "die shrink" - literally reducing the masks and seeing if the logic still works - or be re-designed in the new technology. Since the new technology always allows higher density, it is logical to try to take advantage of it to reduce the chip count, with all the ancillary benefits, one of which is cost reduction.


I really have to thank each and every one of you for your time with this question. I've learned a lot just within 24 hours. Guess the only thing I must decide for myself now is if I can get to love the rounded window as much as I loved the square one on my original HP 41.
Thanks guys!



Why not get one of each? :^)


Well, at the moment there are people in the UK selling mint unopened CX's on eBay as well as in some stores- and they are all halfnuts. Don't know if I'd dare buying used CX via eBay really.....but your idea is OK with me :)


Ted - which stores?

(Bank manager in full panic mode now!)


James, email me on that one!


I just bought a used 41 CV fullnut on e-bay.

The seller concealed the fact that the battery terminals were corroded. Would not work until I took it apart, and cleaned--corrosion even got into the contacts on the main PCB.

(By the way, I learned how to open it up safely by going to the excellent write up here in the museum--written by Stefan Vorkoetter, found in the articles forum, under "reapairs")

In every other way, a brand new looking unit. I do not think the original owner ever used it.

Caveat Emptor.

But now she works, anyway.

I also bought a 48g dud, similar situation. Seller said it works, but it didn't. He said "Sorry about your luck--claim it on the postage insurance---which the post office of course refused because the shipping package was pristine.

So now I know what's going on in some cases:

1. seller sells a dud (and buyer is supposed to understand this somehow)

2. Buyer buys, with "postal insurace"

3. Buyer takes package after receiving it, and beats it up a bit,

4. Buyer requests postage receipt, takes mess to post office, and claims!

Seems like a scam, and I bet it happens more and more on EBAY.


Hi, Bill;

is your 48G still needing assistance or you alredy have it working? If so, let us know. Maybe help is available...

Luiz C. Vieira - Brazil



Thanks for asking. Actually, I have not done anything with it yet.

I have read a couple of different articles on performing surgery on the 48 series, and it certainly seems like quite a bit of work, so I have not started to explore, yet.

As it only cost me $30 USD (inlcuding all costs) I have not been too compelled to go after it, yet. But certainly moral support makes all the difference....





The seller of the corroded unit was very apologetic (I wrote him a nice note--not a mean one) and he agreed to either totally refund my money, OR give me compensation for the unknown damage. In fact, we came to a good agreement on the real worth of the machine, and all parties are happy.

So far, in my small e-bay experience, I have only one true "dud" out of eleven (11) purchases.

Ebay is rather remarkable (in a good way, I think)



I'll second that - so far I've only had good fortune with ebay purchases - my first 41CV was in very good condition, perfect battery contacts (with new batteries but shipped outside the calculator) and all covers, including the side cover, present other than for one port which had a real estate module in it, and all 4 rubber feet.

My second backup 41CV was also in good condition, all feet and all covers apart from ports that had modules in. I bought it mainly for one of the modules, it was advertised as a 41C but turned out to be a 41CV.

Also picked up a very good refurbished card reader which looks like new.

The only problem purchase I had was a 12C with 5 non-working keys - the vendor readily offered to replace it but my curiosity got the better of me and with assistance from contributors on this forum I was able to diagnose and fix it.

The only problem with ebay I have had so far is trying hard not to get carried away! Only had limited success with this!


SNIP>>The only problem with ebay I have had so far is trying hard not to get carried away! Only had limited success with this!<<END SNIP

Yes, I already have my wife saying, "not another CALCULATOR!" or, "O.K., what are you buying THIS time?!" or, "there goes the money for our new mattress....."

And I only started buying calculators about 3 months ago when I went to buy a second 32sii and found them out of production.

The world is truly full of temptations. Fortunately some are more benign than others!




Hi Bill

Yeah, I only started buying a couple of months ago when the battery in my Casio expired (buying a new battery was way to logical for me!). As the house is empty during the day I got my purchases delivered to the office - my colleagues thought I was nuts spending $100+ on a used calculator and that was before they found out it has no equals key! Their eyes glaze over when I start on stacks and roll-downs / ups!

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