HP-41CX
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Both of my hp82341A printers suffer from the same problem: The paper advance is not working properly anymore, as you can see from the picture.
When the paper is not advanced as it should be, the printer writes the lines ontop of eachother. I checked the printer before already, everything looks fine. Thus most likely the Rubber Wheels and the Roller Pinchs are worn out, not soft enough. A replacemenet of Roller and Wheels would be ideal, whoever the service manual doesn't tell any diameters or widths.
So first step is to disassable the printer.
Disassmbling the printer was almost no problem, thanks to the service manual. However, removing the flexible PCB from its connector was quite tricky. hp advices you to take a special tool but naturally this tool is not available. I built myself a tool, just a piece of stiff cardboard.
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In this blog I describe how I refurbished my hp battery pack 82033A.
In order to run the Printer 82143A or the Cassette Drive 82161A it is mandatory to use this battery pack, that can provide higher currents, which cannot be provided with the standard hp AC power supply.
The 82033A battery pack originally consists of 4 NiCad rechargeable batteries, 1,2 V. Naturally, after more than 30 years in service those batteries are not working anymore. Even worse, some of them are leaking.
The procedure to change the batteries is relatively simple...
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After a repair of broken screw posts my HP-41CX (coconut) runs very satisfying, almost without any problem. (I can’t say if the below mentioned problem existed before, I haven’t used the CX for years).
BUT - the time in the CX runs much faster than it should. One minute standard earth time means 2:56 minutes in the CX universe. With this big delta to the real time the Correct function does not help. Did anyone come across this problem? Does anybody have a hint what can be the reason?
All commands of the Timer Module U11 work correct, no problem at all (Date, CLKT, DDAYS, etc.), thus I hope that the problem is outside of the U11 (HP Part Number 01LF6-0001).
The Timer U11 uses a crystal / quartz Y1 with a parallel switched resistor R4 (22 MΩ).
Has anybody seen a specification of the Quartz/Crystal (HP Part Number 0410-1381)?
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01.04.2014
The world most famous and in my opinion best handheld computer in the world was and is the HP-41C/CV/CX of Hewlett-Packard. Build and sold in the 80s it has reached "cult status" and a worldwide community of HP-41 enthusiast are keeping the information about it alive.
I can call a HP-41CX my own, which accompanied me during my studies. It was exactly that what a student needed in the 80s, studying electrical engineering. Together with a Math-Module and a card reader at least the electronical support in the exams was perfect.
After several years passed by without touching the device I found out last week that my beloved HP-41CX was "dead" even though powered up with new batteries. Even worse, after I took out the card eader, I noticed that I could spread the upper and lower cover at the upper part of the hp easily.
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First step is to remove the screws which keep the hp41 together, usually. The screws are located under the rubber feet, and under a grey foil, at least in my model.
After I opened the calculator it became immediately clear that the screw posts, which task it is to support the screws to put proper pressure onto the contacts of the key- and mainboard. Without proper posts the contact between different parts of the hp won't work correctly. A known problem.
As you can see on the picture the area around the upper screw holes at the lower cover were broken. In addition at the upper part the inner 2 of the "guidance" pins between the upper posts were broken not able to keep the in the right position.
Furthermore the right post of the lower ones was broken. Altogether a quite substantial damage even though my hp war treated gently in drawer.