[41CL] Alternative serial connector, saving a port


I hesitated for a long time to include a serial connection with my 41CL in order not to lose a physical port. Finally decided to try an alternative solution which is not as elegant as Monte’s serial port design but saved me a physical port and allowed me to utilize the battery charge port on the side (especially since it was missing the cover). I am sure it can be improved. I routed the serial connection wires through the two holes on the side by drilling to the side of one of them. After soldering the stereo female connector, I used a super glue to attach the connector inside the charge port flush to the battery holder. The tip of the stereo jack is almost flush (within <1mm) with the calculator when you look from the top. I used AeroMicro insta-set glue accelerant with ZAP Plasti-zap Medium CA super glue. If I have to make any repairs in the future, there is still enough room in the side port hole for a fine soldering iron. I hope you find it useful. Now transferring to/from 41CL is a simple and fast process.


Edited: 2 July 2012, 8:00 p.m.


Nice and creative approach Kerem, who said engineering was a thing of the past?

Thanks for sharing the idea, the pics say it all. Good job you did - congrats on the mods.



I second Angel, congratulations.

I am still trying to find a -safe- way to buy and 'grab' at least one 41CL mainboard (two would be even better). I have the $$$ for the two units, just miss the safe means to bring them. And I have two good HP41CV 'bodies' just waiting to 'incorporate' them.


Luiz (Brazil)


Hi, Luiz

Bom dia


I am still trying to find a -safe- way to buy and 'grab' at least one 41CL mainboard (two would be even better). I have the $$$ for the two units, just miss the safe means to bring them.

"Monte" helped me very much with the Customs Forms. Just send me an e-mail so I will tell you how this happened.


OK, obrigado! (thanks!)

Will contact you soon.


Luiz (Brasil)


I'd be interested as well. I was recently given a fullnut 41CV, but I don't want to open it. What should I get, another 41CV or a 41C? Thanks!


Hi, Gerson.

As you get your 41CL, please drop me a line. I think I can provide you a 41 case, free of charge. The only problem might be the module/IO assembly. I have at least four ones in the need of a new flex circuit. I guess Diego is the one that would save the day... but then again, the 'unsafe-way-of-buying-foreign-stuff' ghost awaits in the dark room... If you find a way to do so, I could pay for three amongst four flex circuits and you'd keep the fourth one so when I provide you the 41 case you'd just have to attach the new flex circuit.

Let me know what you think of it. Feel free contacting me by e-mail.


Luiz (Brazil)


Thank you, Luiz! I'll call it HP-41LCV when it's ready :-)


Hi Gerson,
My suggestion would be is to use the HP-41C instead of CV unless there is another reason for collectors point of view. Simply I would use the C because it lacks the capabilities of CV (memory etc.) Then you can use NoV-64 or Clonix-D modules with CV and CL to further expand their capabilities.


Olá, Gerson.

Both models will work with 41CL board, since they are fullnut versions as mentioned in "41CL Manual".(Is there a 41C halfnut version???)

I have also one 41CV that I prefer to keep intact and recently purchased one 41C (tall keys) to upgrade into a 41CL. It's really a incredible machine...

Just one point, here in Brazil is getting hard to find 41 machines in good shape and when we find, they costs very much...(as you know).



Thank you Jamil and Kerem for your suggestions. Once I have a suitable case, I'll go for the CL board.


Just one point, here in Brazil is getting hard to find 41 machines in good shape and when we find, they costs very much...(as you know).

I would gladly trade an HP-41CV for a Brazilian "Prestige" version of the HP-12C.

Mark Hardman

Houston, TX


I still have one, NIB (B from Blister, factory sealed). Wouldn't you have a bare CX, just the bare working calculator, no need for protective case, batteries holder, neither the I/O port covers? If so, drop me a line.

l/i/n/u/x _ l/c/v (at) y a h o o DOT c\o\m.br


Luiz (Brazil)

Edited: 3 July 2012, 3:33 p.m.


Olá Luiz,

Does yours do trigs? Mine does and gets the same forensic test result the HP-41CX does :-)

I won't trade mine, at least for the time being. I'll keep an eye on the market trends :-) Good luck for both of you!

Thanks again for your kind offer.



Do you know what I like it the most? The blueish color against the brass. I like them blue...

Thanks for your support, fellow country-mate!


Luiz (Yep, still there...)


Yes, the blueish body is very cool! :-)
It's a pity I didn't pay attention to them when they were widely available.





You've got mail.

Mark Hardman

Houston, TX


Ángel and Luiz, thank you for your kind comments. This is nothing compare to what Monte, Ángel, Diego, Geir and others have done. Nice to hear positive comments from the Master's.

One more thing I wanted to mention:

The stereo connector could easily fit into a hole through the side port cover. All you need to do is drill a hole large enough, fit the connector through and glue the connector to inside the side cover. However the side covers are already physically and mechanically challenged. The plastic wings on the sides break very easily. Although it would look more elegant, perhaps wouldn't be a good idea unless it is also secured to the calculator.


Kerem, I'm glad that you got it to work. It's certainly an option for anyone who doesn't want to tie up a Port. My initial thought was to use the side port for the serial connector. But I figured that this option was probably too complicated for a lot of users to implement. Hence my Port Cover implementation. I also didn't like the thought of leaving the side port partially uncovered.


Hi Monte, I knew you had a plan :) Serial port would have been great, unfortunately the JTAG software is too expensive. I agree with you about leaving the side port partially uncovered. Since I was missing the port cover in the first place, didn't make too much of difference. However I am keep thinking ways to cover it, short of any elegant solutions, I am leaning towards using black silicone like material to cover rest of the port. Having the serial connectivity is so convenient updating ROM images in the RAM or Flash, transferring files back and forth.

SD card would be a great tool as well. A micro SD card reader could be placed in the side port and cover could be used to keep it closed. I think there is enough room.


Hi Kerem, Hi all!

Compliments for your job first of all

Actually I thought, before to order the connector already plugged in the rom slot cover, toghether with the CL board, to this solution (the charger connector slot I mean, not ofcourse to your personal engeneering job), in way to keep one more port free, but then before to write to Monte I changed my mind:
I think infact that it's better to keep the charger port free, expecially with the 41CL which requires more power than the others...and for this reason, I think, it should be reccomended the use of a battery pack in place of the more used alkaline cells holder, what do you think about?


Edited: 4 July 2012, 4:06 p.m. after one or more responses were posted


Thank you for the compliment. I use my 41CL every day and power consumption never has been an issue. Although I don't do any FLASH burns which can consume more power. There is plenty of RAM. My batteries last about 4-5 months which I cannot complain, they are relatively cheap. Also I have rechargable N cell batteries that I can charge on a conventional AA charger with an adaptor. However they hold less power than regular N cell batteries, and the battery pack holds even less power than the rechargable N cell batteries, therefore I only use Alkaline N cell (wish there were Lithium N cell). The stereo connector is only 1cm long. I will check the tolerances within the calculator to see if there is any room that connector can be mounted through the side of the body. If there is room, tip is long enough and it can be easily glued to the side from inside. There is definetly room for improvement.

Enjoy your 41CL, it is a great machine with a strong team behind it and lots of labor of love.

Edited: 4 July 2012, 4:05 p.m.


Hi Kerem, just for my personal kwnoledge, how much cost in your shops N alkaline cells? here for a quartet you should spend around 6-8 EUROS
Actually I was worry in the past just using the card reader with cells for the consumption..maybe (I live near to Genova) it's thrue the said that we. like the Scottish people are like Scrooge with money...I don't know exactly how to translate this said, excuse me.
I please somebody from Scotland to tell me that it's not so....)=:
Thanks again

Edited: 4 July 2012, 4:22 p.m.


Hi, I buy them in bulk [from] battery junction. I had good luck with Duracell procell batteries. Quantities 1-23 is $1.19 each. Sometimes even lower. I am not sure what is the best way to obtain these batteries in Europe. A pack of N cell batteries cost less than a MD Happy Meal(Or a pint of Guinness), last longer and no calories ;) Cheers...


Ciao Kerem, thank-you for your answer and thank-you for the link.
I just want to join my compliments to yours for the Monte's job: actually the CL is a little jewel!
For the "consumption" issue actually I must say that I was personally worried cause of the reports I read here and in other places in matter of extra power need.
By the way , personally, I have not yet experieced it and I must say indeed that since a couple of months, the time I'm enjoying this calculator, cells are still alive....
So that any my thought upon this matter was actually based on what I read about, on "said".
I'll be glad to know the experience of other fans of this lovely "neoclassic" calculator as I like to define it.

Cheers from Italy


Edited: 6 July 2012, 3:10 p.m.

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