Which Model HP-41C For the 41CL Transplant?


I have nine working HP-41's to choose from. I only have a single HP-41C, so I don't want to use that one.

Of the remaining machines, one is a NIB HP-41CV that has only rarely seen the light of day. I'm tempted to use this calculator as it would likely have the longest useable life span and would be the least likely to have broken posts. However, I would have to sacrifice a port and a time module to make it fully functional as a 41CL. I also run the risk that once opened, I'll find the wrong type of zebra connector.

Would it be better to use one of my HP-41CX's? I know they all have good posts and the correct zebra connector.

Is there any advantage to using a 41CX over a 41CV?

Mark Hardman


This is a good struggle to find yourself in, better than not having any suitable donor :-)

Because the TIME module needs to be added to get the timer functional, I'd definitely use a CV over a CX - and if you had more then I'd use the (plain) C - my preferred choice, going from the smallest to the biggest.

In that way you'll still have 7 CX's (fully functional) plus the CL and your "token" C.

Good luck with the transplant!


I appreciate your answer. I had to go back and re-read the 41CL manual--and you are correct. Regardless of the model used, a time module is required. So using a 41CX gains me nothing and really would be overkill.

I just received confirmation from Monte that my board is on its way. The donor 41CV has been opened and inspected.

Christmas is coming about a month early at my house!

Mark Hardman


Regardless of the model used, a time module is required.

Not true, see Time chip inside 41CL. If you use a CX it's possible to use its timer chip instead of a TIME module.


Technically I guess that's correct but I'm not inclined to get into that kind of intermediate-surgery and very much prefer using a physical TIME module.

Besides, what else do you need the ports on the CL for? :-)


What do you need the ports for?

Printer, Card reader


HP IL module


Clonix to load new roms into the 41CL

One port is gone with the serial connector if installed.

Might start running out of ports!


But, I do have a physical TIME module installed in my 41CL which is soon on its way back to me.


Back in 1979-80 with silver prices soaring, many people sold all the silver they could get their hands on. Most of the silver sold was melted down, refined and poured into ingots.

Common (at the time) silver coins were one of the things sold and melted. After all, those common coins had no collector value, but at those silver prices those old coins were worth a lot just for the metal they contained.

Now coin collectors have discovered that what once was common is now rare since so many were melted, and some of what was once rare is considered common since so many were NOT melted.


I wonder what HP-41's will be considered common or rare in another 20 years? Will the 41CL cause a significant loss of 41C or CV models leading to a "glut" of the 41CX?

I don't think there is any way to second guess or predict. I find it simply an interesting thought experiment.


If you don't attach the 41CL label to the case and keep the

old cpu board (guys, PLEASE don't throw them away), it's easy

to change a CL back to what it started out as.

Actually, the 41CL will always be rare, given that I'm not

really expecting to make a ton of them. That, plus the FPGA

and Flash memory are only guaranteed for 20 years.


the FPGA and Flash memory are only guaranteed for 20 years.

you mean to say no more CL fun after 70? :-)

Edited: 2 Dec 2011, 9:22 a.m.


The 20 years is what the Flash manufacturers guarantee. Since

as far as I know the failure mechanism is charge loss on the

floating gates, reflashing the memory and the fpga should be

sufficient to extend the life. Of course there is no guarantee

that the tools will still exist or work in that timeframe. But

since the design is done in Verilog HDL presumably it could be

moved to whatever technology is common in the future.



One of the happiest days in my life, Santa came early! just received my HP-41CL today.
Monte, thank you so much for this “Beautiful Functional Art”; it is not only an elegant high technology core for the classic HP-41 but also it is beautiful from both design and manufacturing aspects. So much to explore and learn about the new HP- 41CL functions and capabilities… Will keep me busy for a long time for sure…

Thank you and Best Regards,Kerem


Three paragraphs into your post, I was under the impression that you were suggesting we melt down our surplus HP-41's!

Just as an HP-41CY commands extreme high prices among collectors,
I would be certain that a well cared for and operational HP-41CL would sell for a king's ransom.

One thing is certain, I will pass away before I offer any of my collection for sale. So, I've given explicit instructions in my will for the liquidation of my HP calculators.

Mark Hardman

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