41CX Needs Serious Help


Hi: This reliable calculator is a gift that served me well for over 20 years with the Math 1 and Advantage modules. 4 Type N batteries; Serial No. 2338S42235.

Low Bat indicator never lit. Problem noticed when Ex Alpha Matrix Function used: Prompts order; I enter 2, 3, & 4. Display always ORDER=5\/ TVM Function (compound interest) OK. I lost manuels but have the user guide. Can't set time, date etc. {Later I foolishly tried clearing Reg & Stack. etc} Cat. #3 still showed the apps. "Invalid Entry" was a typical response for all Alpha cmds. Later, unable to store intermediate calc via: STO 00,01,02... Regular Calc. operated OK then.

Removed battery pack to "reset things." Blank display after installing 30 sec later. Cleaned contacts; found cells were 1.2 V each - why no lo bat indicator? Before I get 4 new ones, how messed up is the data structure? I likely made it worse, but had to get Cramer's rule working. Sorry if this is long. Dan. ICT, KS.


It can be hard to reset things by removing the batteries. The internal cap can keep the memory alive for over a month. For a well and truly reset machine, you have to open it up and short the two big caps out.

1.2V is a good voltage. It is the standard cell voltage of the NiCad pack The low bat comes on around 1V per cell.


Discharging the electrolitic capacitors seems reasonable. Given that the unit came with 1.5 V Alkalines, 1.2 V/cell seems low but OK for a NiCad. Are there 4 screws - Allen, Spleen, Torx hiding under the rubber feet? They are not visable, and I don't want to pry on the case just yet. What should I expect after a reset?


Reverse (all) the batteries and plug the battery holder in for a few seconds, then go back to normal. This will discharge the caps and should normally get your machine running again.



I agree with your concept. My only concern is that there should be reverse biased diodes across a power supply. If so, they would shunt the reversed current to ground and could burn out - to a permanent short. The battery pack is out while I gather info. Thanks.

{For matrix operations, HP's 48g2 is a minimum but no RPN keyboard! Leads me to a 49G+. While a graphing calculator is nice I don't need it. I could learn how to program the 41 CX which I may need to anyway! The trig functions sinh and cosh are abailable using the natural log function repeatedly.} :-(


Sounds like the HP-42S would be the perfect calculator for you (it has the matrix functionality, is not complicated by fancy graphing functionality you don't need, and it's actually easier to program than the 41CX)...

If you don't mind the rather steep prices they tend to fetch on eBay, at least!


Thanks for the information. Both the 42S and the 33S are replacement candidates. RPN operation is for me essential, which it seems is no longer offered by HP - only RPL. When crunching numbers, I simply can't worry about whether or not my keyboard algebra is "still correct". User Programming is required for only a few simple functions. (If sinh and cosh are in the Advantage or Math 1 Application Packs, then the 41CV/X is just fine.) I'll buy a replacement 41CV.

Are there any new HP scientific's that have RPN? Perhaps RPL is also offered for those such as I, who have not written a program for a decade, as well as regular programmers.



The 33S is a true, 4-level stack RPN calculator. (It also has an algebraic mode, but that can be ignored.) It has hyperbolic functions on the keyboard. However, if you don't mind spending at least 3 or 4 times as much, the 42S is one to get. It has hyperbolic functions, although they are not accessible directly from the keyboard. They can be assigned to a custom menu, which can be easily accessed when needed.

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