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HP-41 internal upgrade. ???? - Printable Version

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HP-41 internal upgrade. ???? - Daniel Sancho - 01-10-2003

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.


Re: HP-41 internal upgrade. ???? - Vieira, Luiz C. (Brazil) - 01-10-2003


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.

Re: HP-41 internal upgrade. ???? - Andreas Müller (GER) - 01-11-2003

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

Re: HP-41 internal upgrade. ???? - Daniel Sancho - 01-11-2003

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,...?


Re: HP-41 internal upgrade. ???? - Vieira, Luiz C. (Brazil) - 01-11-2003

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.