Halfnut vs Fullnut

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Halfnut vs Fullnut

Postby jotne » Mon Nov 24, 2008 9:07 pm

The HP-41 was made in two different version.
Fullnut and Fullnut

The first versio was Fullnut.
It does have a CPU board innside the the unit.
The big problem with this was the plastic holding the screw for the cover.
They break quit easely and the CPU board does loos its conntection with the keyboard.
Here is a picture showing a workaround using two nuts to make it stick.
This 41C does also have to memory modules added internaly.
P5110154.jpg (111.17 KiB) Viewed 5307 times

The new version, Halfnut does has a new design, no CPU board. The only board is the CX time module.
P5110165.jpg (101.66 KiB) Viewed 5307 times

How to see the difference on the two version on the outside?
Look at the display.
The Fullnut does have square corner on the display.
HP41C.jpg (265.69 KiB) Viewed 5309 times

The Halfnut has rounded corner.
HP-41CV-M.jpg (138.24 KiB) Viewed 5306 times
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Re: Halfnut vs Fullnut

Postby Drulli » Wed Mar 19, 2014 7:38 pm

Hi jotne,
I try to find out if my hp41cx bought in '83 is halfnut or coconut.
You Pictures would be helful however I cannot see them.

It Looks like a broken reference to the pics.
If so, can you repaste the Pictures in?

Can the type be determined by the Serial number?

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Re: Halfnut vs Fullnut

Postby Garth » Wed Mar 19, 2014 9:26 pm

This picture on Geir Isene's website (linked in this website's links page):


shows a Halfnut. Note the rounded corners of the display. The Coconut's display corners are square. This is the first giveaway, since the insides are not immediately visible. The Halfnut started selling in '85, which would mean serial numbers starting with 25. Note that HP never had a "Fullnut" however. This is a name the HP-41 community uses to refer to the models before the Halfnut; but HP codenamed the original the "Coconut" (which came out in 1979); and then in the early planning stages of the next version (in 1983), there was talk of cutting the manufacturing cost in half by cutting down to two ports and cutting the IC count in half, so it was natural to give it the code name "Halfnut." They reduced the IC count more than half but fortunately kept the four ports, and made a slightly better unit that's more reliable too. Many users won't notice any real difference.
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Re: Halfnut vs Fullnut

Postby Drulli » Thu Mar 20, 2014 8:41 pm

Thanks Garth,
my hp is definetly a coconut. It has square corners.
Meanwhile I opened it and made some photos and put them on the Internet. I will start a separate threat about it that everybody can see them.
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