HP-86B keyboard repair

[Benoit Maag]

A well-known problem with the HP-86 keyboard is key sticking as a results of splitting of the underlying square plastic key stems. There is a fix proposed by Tech Tangents on YouTube but it requires desoldering every key and 3D printing of 91 very difficult key stems.

https://youtu.be/4DPMTiUihQc?si=NkviKj7KpdfxUOyH

Does anyone know another way? Glue the little corners without overspill? Fuse the stem corners with heat?

[Martin Hepperle]

During the last years I have fixed several HP-85 keyboards.

So far I never had to desolder key switches.

It is possible to extract the old "plunger" and insert a 3D printed part without destroying the mechanism.

Note that there were two different types of HiTek keys used in Series-80 machines.
One type has four thin "feet" extending downwards and the other type dose not have them and has slightly different dimensions.
So far I only designed and manufactured the type with the four prongs.

In my experience the best results are obtained with resin printed parts as the plungers must be rather accurate and smooth to work satisfactorily.

Martin

PS: some 3D printable models are available in my repository https://github.com/MartinHepperle/HP-ReproParts