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Full Version: HP-41 internal upgrade. ????
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When I buyed my actual HP-41CV I find inside a circuit:

I put here two images: http://www.teclas.org/HP-Question.htm

Can anybody tell me what is? Thanks.



I am not sure about it, but the most common "upgrade" is the speed-up circuit. As the IC's are scraped and no ID to confirm, the best shot is to redraw the connections and check with the original (I should dig-in these five PC's and nine hard drives... but I'm needing it, too.)

Anyway, it's also normal to find a switch, usually a magnetic switch or a dip-switch, to "start" the faster clock. Have you found something like this? I also heard that, depending on the speed-up design, turning the calcualtor ON with an specific key pressed would toggle from speedy to normal.

Anyway, let's hear form the others. I'm curious, too.

Best regards.

Hi Daniel,

try the hint of Luiz. Do a 'Beep'. Does your HP-41 'Beep' normal or faster? Then try to press 'Alpha' and 'User' at the same time. Do a 'Beep' again. Does the speed of the 'Beep' change? I think it should.

Best regards, Andreas

Muito obrigado Luiz, vielen dank Andreas:

The problem is that I can not test it because I unsoldered this upgrade as you can see in the images. That's because I like to have the machines original.
But I had curiosity to know if anibody was able to say me if it is an interesting upgrade.

was it a comercial upgrade, a kit,...?


Hola, Daniel; mi placer poder ayudarle.

I'll post what I heard about it. I never had one of this, but I'll add one "turbo" add-on as soon as I have time to build one.

What I know is that:

- in some cases, it is incompatible with some clock-dependant devices; some 82104A card readers were mentioned as not working correctly with some speedy 41's
- it enhances power consumption, reducing battery life.

Other then these "features", it is harmless for the calculator itself.

About availability, I was also told that it was fairly available in Deutschland (your 41 came from there, right?) as a kit, not exactly as a "commercialy availble" merchandise. I saw some different "versions", one of them with a magnetic switch mounted inside the calculator, aligned with the middle frame. This way, a small magnet could be used to toggle from "speedy" to normal. Others, as mentioned, used dip switch or key combinations/sequencies.

That's all I know from other contributors at the MoHPC.

Hope these informations are acurate (if I did not change them) and helpfull.