HP-41 CX

[Jon]

Hello:

I have bought a HP-41CX halfnut with faulty working "user key". Sometimes it works sometimes not. Don´t worry, I knew it and I got a very good price (good seller).
May be somebody knows if it can be fixed anyway.
I have also a 41CV halfnut. Could I use it´s keyboard for the 41CX?. If it is possible, can I change the "HEWLETT PACKARD 41CX" logo from the original to the CV`s keyboard?

Thank´s in advance

Jon

[Massimo Gnerucci (Italy)]

You could also use SF 27 / CF 27 to get in and out of user mode... :)

Massimo

[Jon]

Oh God!

I didn´t realize there is another thread for the 41 keyboard repair. Anyway may somebody has an special solution for the user key.

Thanks to Massimo for the alternative. It is a good idea if can´t repair the contact

[David Smith]

See the threads on HP keyboard repair. The user key is just another key on the keyboard. Its' contact is easily cleanable using the "wire brush" technique.

[db (martinez, ca.)]

David has a good first idea. It may just be me but i have had more dirty on/user/prgm/alpha keys than any other and they can be cleaned out. Be gentle.

[Jon]

The problem was the plastic foil under the batteries. After cleaning the key several times with isopropilic alcohol I didn´t get any result until I forgot placing that foil. It seems this element produced any bad contact. So I made the hole for the contacts 1 mm wider and now everything works. YAHOO!!! (and I have the cleanest user key of the world).

This is the first time I open a halfnut. Although it works fantastic it seems it has been serviced. There are two diodes and a capacitor soldered one over the other on one side. I see also red wire connecting two points. Has anybody a photograph of one of these calcs opened. In the main page I have only found a fullnut inner photographs.

Jon

[Vieira, Luiz C. (Brazil)]

Hi;

I posted a photo a few days days ago showing an opened (dismanteled) halfnut and these components are present in at least eight halfnuts I have already opened (two CX and six CV). You may also notice that earlier halfnuts have a post-production cut in the cooper trail where the red wire is soldered, while the newer units have this trail already separated in the PCB layout.

I've been served by a provider that does not care a damm dot for its customers, so the page I was using was removed and created again and all my pictures are gone. I'm lucky I have all of them, so I'll have to upload them all back.

If you want, I can e-mail you the image so you can check if yours is the same type.

Best regards.

Luiz C. Vieria - Brazil

[Vieira, Luiz C. (Brazil)]

Hi;

look at the picture below:

The extra black&red wires in the top of the image were added to test the unit with an external battery pack, they do not exist in regualr units. I don't know how long will it survive again, so if you like it, copy it to your HD...

Regards.

Luiz C. Vieira - Brazil

Edited: 21 June 2003, 12:00 p.m.

[Massimo Gnerucci (Italy)]

Luiz,

would you be so kind to reload the picture about the comma/dot jumper on the spice series?
I wasn't fast enough and couldn't see it...

Thanks a lot,
Massimo

[Vieira, Luiz C. (Brazil)]

Hi, Massimo;

long time, no "read"...

Here it is:

I'm organizing the images so I'll keep them in one directory in my working HD. If (when?) it happens again I'll quickly put them back. I'll "collecting" them around because I have four computer connected to each other (my own home net) and there are at least 3 hard-disks where some images are stored...

Thank you and best regards.

Luiz C. Vieira - Brazil

Edited: 21 June 2003, 1:27 p.m.

[Massimo Gnerucci (Italy)]

Thank you very much, Luiz!
Now I've stored it on one of my PCs too... it will hardly get lost again ;-)

Greetings,
Massimo

[David Smith]

The diodes and caps and wires are standard construction for the halfnuts.

BTW, when opening a halfnut be very careful of the speaker wires. They just LOVE to break off the circuit board.

[Jon]

Thank you.

I see it hasn´t been modified. It´s no the best design I have seen from HP.

Jon

[db (martinez, ca.)]

I never met an hp41 speaker wire i could not do without. The only time i ever used the noise function on purpose was to set up my 41 with the ppc rom to be a piano. I handed it to a friend who plays keyboard. He hit all the keys once and proceeded to play "Mary Had a Little Lamb". OK, it wasn't Mussorgsky's "Pictures at an Exhibition" but i was impressed.

[Ellis Easley]

Maybe that's because when we first go to the machine, we turn it on and whatever bits are on our fingertips fall off and into the gaps around the On/User switch.

[db (martinez, ca.)]

It has gotten no worse since i started to keep the calc in a baggie. With that tidbit it makes even more sense.