Musings and comments about our common interest
I have prepared an early HP41C (serial number 1944A...). I write it here because initially I put it on sale with not good enough pictures, but now it comes in all its beauty.
It is so early a model that it has tall keys and the original, early metal plate keyboard surface (not textured plastic)
I have found an error in the HP41 repair book - in the part referring to the card reader repair.
It is about the order or the cables leading to the electric motor. The black cable is the one furthest from the calculator; the red one is the closed to the calculator. The book said the opposite (or could be understood as the oppositce - it is strange to me since I knew the right order!
Here is a picture illustrating what I say: it is the two cables on the left. The upper part is towards the calculator.
Finally it is here!! 133 pages of our repair experiences and methods. Thanks also to the help and advices of Ignacio Sánchez, who suggested many of the repair methods and helped testing them.
You can click on the link below:
It is also available on all amazon country sites.
Here is the chapter list:
We are in the final stages of writing a book on HP41 repair. We expect to have it finished by the end of September. In our experience you do not need to have any electronics knowledge to repair 80% of HP41's damages. The nature of many of these is either mechanic or bad connections due to corrosion. The focus of this book is on that 80%. It is written for those of you that wouldn't dare to repair your calculator before!
Here are some of the chapters:
The target price will be 9,99€ for the kindle version a 2-3 € more for the print version, and will be sold through amazon.com and on this website. I'll keep you posted through this channel. Do not hesitate to bring suggestions for additional content!
We are finalizing the design of three different products. As they are not fully prepared, we'll show them in 3D printing form. We will present it during three blog installments.
Until now we have been using a test order of zebra PCB circuits ( Zebra PCB version 3)
We have just received the definitive version (v4) which has a slightly modified dimension to have a better fit (we're talking tenths of mm) and a more precise alignment of tracks.
All orders received this week end are already supplied with the new model
We have introduced a new product. This is only for those that want to use the HPCL circuit on an old HP41c (with serial number before 1954AXXXXX). The screen set requires that the processor have specific capacitance. This is provided by the processor that came with the machines, but not by later processors (in case the original became defective) or if you want to install a CL super-processor. So we have bought a pile of 10nF surface-soldered capacitors, to install between two parallel circuit lines. We will provide instructions if needed:
We have done more tests and now we have put it for sale: it works well. Now thinking about packaging to send them in the best way - so that the adhesive stays put until installation. Alternatives are mounting it on a lower post assembly, or another clipping method to maintain the pressure between up and down.
Further pictures on the first production run:
You can see now some more pictures of the new zebra model:
In continuation of a previous blog entry about a new series of educational videos on HP graphical calculators, here are chapters 2 and 3:
And here is chapter 3: