HP-41 Quiz (big, contains pictures)


Recently, I stumbled across a strange HP-41CV. It has no LCD display, the battery compartment is closed with a fawn cover, and on the side, there is a cable with a plug at the end (labeled 82106A memory module):

After thinking some minutes what this device is all about, I found the solution. It is a .... STOP. I know the folks here likes quiz games :-) And this one is not too difficult. But the only prize I can offer is a picture of the inside of this device.

Enjoy, Juergen


Hi Juergen,

Okay, I'm game - here's two guesses:

1. Ports expander.

2. Memory expander.



(semi)-remote keyboard?


OK, Here's what I think we know:

  1. Fawn colored cover on the back where the batteries go
  2. Cable emerging from AC power port
  3. No display
  4. Cable terminates in a module reading "82106A"

OK, so #1 #2 and #3 clearly point to a homebrew project of some kind. In light of that, #4 is a red herring, since a hacker could implement just about anything inside an 82106A case. (Hi, Diego!) #3 clearly implies that processing for local consumption is not a feature of this device. #2 says the same thing. So what's inside the box that could be a resource for an external 41C? Probably not another 41C. I doubt the 41C electronics would be happy running without an LCD, so I'd guess that the case is just an enclosure for something.

What could that be? Well, if you replace the PCBs, practically anything. But what is a 41C case good at holding, other than the PCBs, keyboard etc? Ah, the modules. You haven't shown us the ports, have you? 8)



I thought of a second processor thing, like the Acorn BBC used to support, but on second thought I also bet on a port replicator.

But then, why would the LCD have been removed?


Because the PCB is gone, not just the display?


Two guesses I know, that's cheating ;)

1) using the 41 "framework" (electronics removed) as a cheap keyboard
2) using the 41 with a speaker box instead of a display for blind people


It doesn't do anything. You see it, you get curious, you open it up, and a spring snake jumps out. 8^)


Thank you all for your guesses which show, on the one hand, your expertise and, on the other hand, your
good sense of humor. I enjoyed the ideas of remote keyboard, dual-core 41, 41 for the blinds, etc.
Now it's time to disclose the secret (well, it's not so secret anymore; you already found the solution):
it is a port replicator. when opening the calculator, I saw that there was no PCB, too:

This might mean a second life for many "cannibalized" HP-41. Unfortunately, I cannot open the
plug because it is glued and I borrowed the calculator from a friend of mine. Thus I cannot
provide the exact connections but probably they can be deduced from information in the HP-41
service manual.

Best Regards,

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