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HP 41C mod - Printable Version

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HP 41C mod - vk6ti - 01-07-2015 12:48 PM

Hi Folks,
Back in the early 80's as an electronic engineering student, I used my HP41C
as a "guinea pig", to change the capacitor on the board, to speed it up and put reed switch in the side, so we could use the card reader at normal speed.( after reading PPC mags) Subsequently I ended up doing a heap of them for fellow students on campus.
Meanwhile 30 years on, and collecting HP stuff and not really working on these type of instruments, so please excuse my ignorance on this simple question.

I was recently repairing a HP41CV, due to battery corrosion, and quickly noticed different board and architecture to what I remember on the 41C,
This is were I start sounding dumb, but were the models after 41C,
ie 41CX and 41CV, able to be modified in the same way as the original 41C ?

It's been a long time, since I have done this sort of thing, but only like to know
out of curiosity


RE: HP 41C mod - Massimo Gnerucci - 01-07-2015 12:58 PM

A quick view of several board types (from Diego's site).

RE: HP 41C mod - vk6ti - 01-07-2015 01:13 PM

Ciao Massimo,
the 41CV I pulled apart seems to be the HalfNut version, as per photos of your link page. Hardly anything to it.
Nice place Milano, will be going there to visit family this year
Mangia e Bere


RE: HP 41C mod - Massimo Gnerucci - 01-07-2015 01:36 PM

Hi Ray,
halfnuts can be easily spotted by their rounded corners in the display. (here's a link in this same site).
And yes: boards were heavily re-engineered in the course of Coconut's life.

Let me know when you'll be in Milan...

RE: HP 41C mod - John W Kercheval - 01-10-2015 08:07 PM

I did that modification myself many times on the UC Berkeley campus in the mid 1980s.

The CV was modifiable. The CX was not. I think certain versions of the C were but i never did any of those. The double speed mod was for the CV.

RE: HP 41C mod - Dave Frederickson - 01-10-2015 08:18 PM

I had a Fullnut CX and put the speedup switch inside the battery compartment.

RE: HP 41C mod - TASP - 03-04-2015 02:20 AM

I have an HP41CX with the magnet activated switch built in. I was able recently to get it back to regular speed (the magnet fell out of the port cover and is long gone).

I didn't do the mod, but I don't remember who I sent it to. Undoubtedly they advertised in PPC Journal.

Except for gronking the card reader, I don't recall any trouble with it at 2X speed, although it makes all the beep tones exceedingly shrill.