41CX alpha mode challenge (help!)


I have a 41CX that is otherwise working except for the alpha toggle, which is totally inoperable. Can anyone come up with a way to enter alpha mode without using the toggle? I don't have a card reader or wand, either. Thanks.


Your most likely problem is a dirty switch contact for the ALPHA key. These can be cleaned fairly easily if you open up the machine (one screw under each rubber foot).

Beneath each key dome is a tiny hole in the circuit board. Make a tiny wire brush out of three wire brush bristles twised together, mounted in a pin vise, and trimmed square. Place a drop of 91% isopropyl alcohol on the hole, dip the wire brush in more alcohol, and gently "scritch" around in the hole with the brush. In stubborn cases you may have to repeat a few times.

While the machine is open, clean all the board and battery contacts with alcohol (including those ender the CPU card in fullnut machines).


Hi, Paul;

I am somehow worried, now. Except for what you already have available through the keyboard, I cannot think of anything else... Two of the "keys" that are more often used in an HP41 are [XEQ] and [ALPHA]; then you have all ALPHA keyboard as an aid to type in the function you want to. What might help you is a card reader with cards that contain assigments to keys so you can use other resources in USER mode OR a wand, but you have none, right? This is because you don't need to perform any specif [XEQ][ALPHA] something [ALPHA] to load from both of them. Also you might load programs with ALPHA messages... Oops, sorry! No further bad mood...

David's suggestions are the ones you must follow. Cleaning the key contacts seems to be the only way out.

Let us know if you need advice. I have some pictures of a disassembled HP41 (in time: is yours a half- or a fullnut?) that may be of help.


Luiz (Brazil)

Edited: 10 Apr 2004, 3:01 p.m.


Paul wrote: I have a 41CX that is otherwise working except for the alpha toggle, which is totally inoperable. Can anyone come up with a way to enter alpha mode without using the toggle?

Is this a trick question? Why not just use the AON command? Assign it to a key for use in USER mode for faster access.

Surely the challenge is how to get _out_ of Alpha mode ;-)

Regards, Wlodek


Neat, but how do you assign AON if ALPHA doesn't work?



Well, you can use its function id (AON = 048C) and use the CCD or any other synthetic method...

Also, to get out of alpha mode, switch the calc off, then on again. Cumbersome, better to get the toggle key cleaned!!


Hi, Angel;

Now I'm curious: is there a way to activate any other function by it's ALPHA name with the use of regular keyboard? I mean, does the CCD allow a way to access a ROM address withou the use of ALPHA? If so, this is something I'd like to know about! 8^)

In time: Paul, this image is available to download. I guess you know it well, but it is probably easier to locate the contacts for the ALPHA key. It is about 120K large.

Hope it helps.

Luiz (Brazil)


Hi Luiz,

Yes, you can always use the function id# to invoke it, no need to spell its full alpha name.

If you use the FDATA function in the SandRom, that will give you any function's (or program) hex id# (end of the info string). For instance AON = 048C hex = 004.140 dec.

The CCD Module has extensions to the normal XEQ function that allow the function digit entry in either dec or hex. Have you ever used it? it's quite nice.



And how do you plan to run the FDATA function, or any other function without pressing ALPHA?

In short. Without ALPHA, you're pretty stuck.
You only have the functions that are already assigned to keys to start with, and possibly functions that modules make available as extensions to the OS.

Such things are the Wand (which gives you the whole keyboard), the Card Reader (which have some functions started by feeding a card) and some extensions in CCD or ZENROM, such as synthetic stuff. But unless I've missed something in CCD, it will not by default change the behaviour of the keys so that you can get any function without first running a function in the CCD. The 41 still works as a 41 by default.



The CCD extensions work making use of the interrupt vectors, thus no need to call them using Alpha. In other words, it alters the normal behavior of the calculator, so the XEQ key for instance always presents the digit prompts as "default".

But of course I agree with your that without a working Alpha key you're pretty much stuck, it was just as a work-around.



Yes, the ZENROM also uses the interrupt vectors.
But it's all to extend the ability to do synthetic stuff.
The actual functions in the module cannot be accessed without pressing alpha. But you have the ability to do such things as RCL d. GTO gets one more mode, ALPHA mode is extended with full lowercase capability, and so on.
But these are all just extensions to the functionality. None of these extensions can help you run functions not assigned to a key. You still need to press XEQ ALPHA name ALPHA to call other functions, including AON.

Now, as I've implied above, I have a ZENROM in my 41, and have no experience with the CCD (unless you count a little playing on an emulator), but I believe the same is true there. You still need a working ALPHA key to call any function not assigned to a key. The fact that the rom hooks into the interrupt vector don't help. It's used to extend the functionality of the calculator, not change it.

But correct me if I'm wrong.

How about just a keystroke summary on how to do AON without using ALPHA?


Hi, Angel;

I don't own a CCD (I wish... and an HEPAX, and...), but I have a copy of the CCD quick reference guide. I think I got it: [XEQ][ENTER] gives an alternative two-byte (dec or hex) entry (ROM address), so you can use [XEQ][ENTER]004.014; is it correct?

Thank you! That's pretty "neat"!


Luiz (Brazil)

Edited: 12 Apr 2004, 10:15 a.m.


Exactly. And if you press "H" the prompts change to:
XEQ '_ _'_ _' meaning hex input is expected.

This is the "normal" behavior of the XEQ key when the CCD is plugged in.

Also, to execute FDATA without switching to Alpha, you can use its own id#: A3:69.



Ah. Well, ignore my previous question.
Here we have the answer.
The CCD module is really neat. I wish I had known about it when I got my ZENROM, since the CCD looks even better.


Another clever thing about the CCD is that you can single-step CAT'2 until you see the function you want, and then press XEQ, and the function is run. - or you can press the A-button to assign the function!
Unfortunately it doesn't work with CAT 3...so it won't solve the original ALPHA-key problem.



I had a prgm key starting to go; I squirted a little
alcohol into it and pressed it a few hundred times,
repeating two or three times, holding the calc upside down
to avoid the alcohol spreading into the rest of the
electronics, then waited a few days before putting
the batteries back in. It works fine.

Not that I wouldn't open a 41 if necessary:




OK, apologies for my previous AON suggestion :-)

Here's a serious one.

Find someone who has a card reader, who would write a card or cards for you and would loan the card reader to you
for a few minutes.

Ask them to make key assignments of the functions and programs that you regularly use that are not on the keyboard. Also create a program
02 AON
03 R/S
05 END
and assign this to a key.

Save the assignments and the program on cards.
Read those cards into your HP-41CV. Give back
the card reader :-)

Then use USER mode to execute the functions and
programs you need.

To enter ALPHA mode for writing text in the ALPHA
register, not function names, press the key to
which program ALPH is assigned.

To quit ALPHA mode, press R/S which will run the
second part of the ALPH program, and turn ALPHA mode

If you use more programs and functions than can be
assigned to the keyboard, you need a second level of
trickery. Write a big program with each function or
command you need given its own label. For example
02 R/S
03 LBL 01
05 R/S
06 LBL 02
08 R/S
09 LBL 03
10 FS? 17
11 R/S
12 LBL 04
14 R/S
and so on

Assign this program to a key for execution in USER

To execute any of the commands in prgram LABELS,
press the key for LABELS in USER mode, then type
XEQ 01 for FACT, XEQ 02 for BEEP, XEQ 03 for FS?17,
XEQ 04 for XEQ "THING", and so on.

This will work. If you can borrow a card reader and an
HP-41 with a working ALPHA key. Admittedly it is far
more complicated than having a working ALPHA contact
and I hope that one of the methods described for
cleaning the contact will work.

Good Luck!



Oops, sorry, my second method - storing in a program - will not work for tests. Test functions will have to be assigned to keys. That includes DSE. ISG is on a key anyway :-)

Wow, what a problem for a software approach! I hope one of the hardware fixes works for you.



Maybe you can try connecting wires to the column x row traces of the keyboard, to allow a external switch to replace the ALPHA key. The schematic diagram of the 41c says that at J2B (a connector), pin 4 is column C5, and pin 6 is Row R5. At C5 x R5 guess what ?

At the CPU chip, C5 is pin 13 and R5 is pin 18 (again according to the schematic).

I know Nelson has a 41C keyboard open, and Luiz would be another source of information.

I think it will work, if done correctly. You could probably get wires out of the case using the side AC adapter slot.


With best regards from the small and happy community of HP fans in Brasil.



Hello Renato, folks;

I'll give it a try and let you know. Yeap, I have (my own) at least one halfnut I can try that. It seems reasonable to me.

Anyway, why not to consider also a cold soldering? It's not too hard to happen, and maybe a single resoldering at the nut CPU terminals would solve the problem. As you have already described the pinout, Renato, following them and checking for fissures with a god lens would also be of help. I've done it and succeed many times, mostly with Voyagers and HP41 halfnuts.

Just another suggestion.

Best regards, folks.

Luiz (Brazil)

Edited: 13 Apr 2004, 2:06 a.m.

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