Exotic Calculator Modifications


Ok folks:

Back at Berkeley in 1985 I did the "capacitor change thing" to double the speed of my HP41CV. Worked great & the calc is still working fine.

Although as you may know my "service machine" is a mint 71B with numerous modules & enhancements including the 41/71 Translator Pac which will run 41 software at roughly 2.5X the speed of my turbo CV.

My question to you is:

What are some other exotic do-it-yourself calculator modifications you have seen or tried? EVEN if you tried and failed.

John in DC


I'll start you off:

Once, I tried ripping open the Time Module and hardwiring it directly inside my 41. Bad idea. That didn't work at all. 41 survived fine, but the Time Module Pac was DOA.



My 71b test machine has an INTERNAL 32K memory and FORTH rom. I have not seen any other 71b with this modification, but know some were changed by third parties back in the 80's/90's. I find it pretty handy, and does not take up extra slots. The daughter card is about 1/2 cm from the Card reader slot, and can be seen by looking through the 3rd and last Memory slot.


Very Good!

I've not heard of that one. My extra RAM comes from the semi-exotic CMT massive RAM in the space of the card reader.

Thus we have the same RAM but your CR slot is free. I own but never used the card reader, preferring instead the Digital Cassette Drive which I use for mass storage.



See my mods at www.kuiprs.nl/museum.htm. My good old HP41C was upgraded with a Time Module, Quad memory and speedup capacitor (with reed switch for getting it back at its original speed. And it still works!



Forgot to mention: I also have a triple XFUN/XMEM/XMEM module!




I think one of the most exotic mods to the HP-41 is the W&W HP-41CY Turbo.

Ok, that was a commercial thing, but it was a very deep mod.

Some time ago I also saw an HP-34C with speech synthesizer (now may be somewhere in southern Europe;-)

Back in the Eighties, a friend of mine and me made a small 'backlight' for the HP-41.

This mod consisted of two _very_ small light bulbs (from ALBA) and a small switch,

like those used with the CY Turbo.

The bulbs were put into the small gaps on the left and right end of the LCD plastic.

It worked fine, but it was more an effect to impress the colleagues,

because the display readability didn't improve when using the 'sidelite'.

Actually, it was better readable when the lites were off;-)

And there were some other side effects,
like higher battery drain and the bulbs getting warm after a short while.

At the same time in the early eighties, some US company offered an external light,

which was mounted on a flexible neck, and connected to the HP-41 via a printer plug.

Very much like the current USB lites for notebooks, but decades earlier.

<OT>ThinkPad users like me have a ThinkLight, of course:-)</OT>





I've heard of the CY Turbo but though it was a joke. Is that thing real? What does "W&W" stand for?

Do you have any links or details on the CY Turbo?


I made an external KeyBoard for my HP 48G+.

Have some pics of it.

I just externalized Calc keys*./

It works fine!

I wanted to double it's speed ( calc speed) but don't know how.



W&W Software Products GmbH is a German company which was founded

back in the Eighties to produce the famous W&W CCD Module.

Later they made and sold various HP calculator related things,

amongst them the W&W HP-41CY Turbo, which is a 'pimped-up' HP-41CX

with a built-in 64K RAM box and a speedup switch.

The optical changes from the standard CX were a different keyboard overlay,

a W&W CY faceplate, and the visible turbo switch on the left side.

I can send you photos of a CY, if you send me a mail to M a g i c 4 8 g e s @ g m x . d e

The hpmuseum forum archives also contain some threads related to the CY.

W&W still exists, but isn't active in the calculator area anymore.

All inquiries regarding CY service will be redirected to me.


BTW: AFAIK W&W initially stood for 'Wilfried and Wolfgang',

the names of the founders Wilfried Koetz and Wolfgang Baltes.

Later Dr. Wolfgang Baltes, who wrote his dissertation about an HP-IL topic, joined HP Grenoble.


Raymond will do.

FYI, I LOVE the anthem Deutschland uber Alles.



Hello Raymond,

I once had one of those HP-34C with a speech synthesizer, It was an amazing calculator: It was modified for blind people so that the content of the display would be "spoken" by the speech synthesizer. They had soldered a connector to the display to capture the digit displayed and this connector would connect to an external black box that contained the speech systhesizer. You could at any time press a button and a robot-like voice would read the digits one after the other. I sold it to someone in Switzerland, I guess it's still there ...


At the same time in the early eighties, some US company offered an external light,
which was mounted on a flexible neck, and connected to the HP-41 via a printer plug.
Very much like the current USB lites for notebooks, but decades earlier.

Ah yes, the Port-X-Light from AME. I have one of those. It uses one of those "grain-of-wheat" bulbs that were so popular before LEDs became commonplace, and has little snap-on bulb covers in different colors. Plug it into a module port and it curves above the keyboard like a miniature gooseneck lamp. That's probably the accessory that attracted the most attention when I used it at the office.

And before anyone asks, no, it's not for sale. :-)


My most exotic modification was a watchog system for a HP-71B running a remote control application for a customer:

Software was stored in an EPROM module, but I experimented unexpected errors and/or system hang, maybe due to ESD, supply transients (there was no batteries), or even HP71B timer bugs (the 1BBBB version). I built a watchdog that monitored the STR signal, in case of no activity (HP71B stopped or hanged), a reset was done and the software restarted automatically.


Edited: 25 Dec 2007, 2:02 p.m.


Back in the 80ies I had a Sharp PC-1500 and expanded its memory from 2k to 55k, in banks where I could program my own Basic commands. I also increased its speed by nearly 2x. Once I hardwired it to work in multi-tasking mode, but the software was not stable enough, so I had to revert to single-tasking. The machine is still working fine, but nowadays I use HPs as calculators.

Best regards


I may remember that Sharp did it "run horizontally" like the 71B so to speak? I think we may have carried it in our store. It did not sell to well but it did have an interface of some kind- I think for used a standard cassette tape player as a storage device.



Correct, it was quite similar to the HP71 in several aspects, although the 71B was faster and more robust. In the USA it was sold as TRS 80 PC2 I think.

The Sharp did have an interface to a cassette recorder and a plotter built in. I remember that I put in a cable to skip the high-pass filter in the cassette output, so I could record (= backup) at higher speeds.

Best regards


Yes, we definitely stocked that one.

Most people who bought Sharps bought the inexpensive scientific one (can't recall the model number) for $35 because they did not want to shell out $100 (in 1984-86) for an HP.

I can't recall the cost of yours but think it was marketed as a "handheld computer" and went for $100-$125. Again we stocked the 71B and it sold through the school store for $425 at first and later down to $399.

Definitely remember that one that you had though. You could interface it with the Sharp Thermal typewriter we sold- a typewriter that printed to thermal paper and had a serial port for interfacing with a computer as well.

John K


I ordered the 41 speed-up kit from Educalc in the 80's but the literature said that it should not be used if you have the IL or double modules. I had both (with a combined HPIL and Ext I/O, ZENROM, and Advantage, for four modules in three ports), so I sent it back. A couple of weeks ago I got the double extended memory, so now I have six modules in four ports, plus the Extended Functions and Time modules and other stuff built into the 41cx.

Edited: 26 Dec 2007, 2:56 p.m.

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